The role of EMI filter for noise suppression
EMI Filters
In today's world, where technology plays a crucial role in our daily lives, electromagnetic compatibility (EMC) has become a significant concern for both individuals and businesses. Electromagnetic interference (EMI) is a common issue that disrupts the proper functioning of electronic devices. However, with the advent of EMI filters, this problem can be effectively addressed. EMI filters play a critical role in ensuring electromagnetic compatibility, reducing noise, and enhancing the performance and reliability of electronic systems. This article will delve into the role of EMI filters, especially in noise suppression and addressing electromagnetic interference.
Noise Suppression
One of the primary functions of EMI filters is noise suppression. Noise, in this context, refers to any unwanted variations in the electrical signal that may affect the performance of electronic devices. Such disturbances can come from a variety of sources, including power lines, radio waves, and other electronic devices. Noise can manifest as conducted or radiated emissions, both of which can be detrimental to the proper functioning of sensitive electronic equipment.
EMI filters help mitigate noise issues by providing a barrier between the power source and the electronic device. These filters act as a buffer, blocking or absorbing unwanted high-frequency noise while allowing the desired power signal to pass through. This allows electronic devices to operate without any disruptions or malfunctions caused by electromagnetic interference.
Electromagnetic Interference
Electromagnetic interference (EMI) occurs when electromagnetic radiation emitted by one electronic device interferes with the operation of another device. This interference can disrupt the functionality of electronic systems, leading to malfunctions or even complete failures. EMI can be particularly problematic in areas where multiple electronic devices are operating in close proximity, such as office buildings or industrial facilities.
EMI filters play a crucial role in managing electromagnetic interference. By incorporating filters at the entry point of electronic systems, such as power supply connections or data ports, EMI can be effectively suppressed. The filters isolate the electromagnetic noise and prevent it from spreading throughout the system, thus ensuring the integrity and reliability of the electronic devices.
Conclusion
Overall, EMI filters play a pivotal role in ensuring electromagnetic compatibility and minimizing the disruptive effects of electromagnetic interference. Whether in single-phase or three-phase applications, these filters provide robust noise suppression, protect electronic devices from external disturbances, and enhance the overall performance and reliability of electrical systems. By incorporating EMI filters, both individuals and businesses can ensure their electronic devices operate smoothly and without any detrimental interference.
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EMI power filter selection considerations
Notes On EMI Power Filter Selection
The main performance indicators of EMI power filter generally include insertion loss, frequency characteristics, impedance matching, rated current value, insulation resistance value, leakage current, physical size and weight, use environment and its own reliability. In the use of the most considered is the rated voltage and current value, insertion loss, leakage current three.
When we choose the power filter, we should mainly consider three aspects of the indicators:
1.The voltage/power supply
Power supplies can be divided into AC power supplies and DC power supplies. Accordingly, many manufacturers of power filters can also be divided into AC and DC.
In principle, the AC power filter can be used for both AC and DC power supplies, but the DC filter can not be used for communication, mainly due to the low voltage resistance of the capacitor in the DC filter, and may have high AC loss and cause overheating. Even the voltage resistance of the DC filter is not a problem because the DC filter uses a large capacity common-mode filter capacitor if the leakage current will exceed the leakage current problem.
Therefore, DC power filters should never be used in AC situations.
Ac filter used in DC situation, from the point of view of safety is no problem, but to pay the cost and volume of the price; In the prototype phase, if you happen to have an AC filter, you can replace the DC filter.
When the working current of the power supply filter exceeds the rated current, the filter will not only be overheated, but also the low frequency filtering performance will be reduced. This is because the inductance in the filter will saturate the magnetic core and reduce the actual inductance in the case of a large current. Therefore, when determining the rated working current of the filter, the maximum working current of the equipment shall prevail to ensure that the filter has good performance under the maximum current state. Otherwise, when the interference appears under the maximum working current state, the equipment will be interfered or the conduction emission will exceed the standard.
When determining the rated current of the filter, a certain margin should be left; In particular, it is customary for people to call the AC "effective value", rather than the AC "peak", leaving a certain margin is very necessary. The rated current value of the general filter should be 1.5 times the actual current value.
2.Followed by insertion loss
From the point of view of interference suppression, insertion loss is the most important index. ? The insertion loss is divided into differential mode insertion loss and common mode insertion loss.
How to use the power filter to determine the required insertion loss?
Firstly, the filter is not installed at the power supply entrance of the equipment, and the conduction emission and conduction sensitivity of the equipment are measured, and compared with the standards to be met, to see how much difference between the two decibels. The role of the filter is to make up for this gap.
3.The last is the structure size
Since the inside of the filter is generally potting, environmental characteristics are not the main problem. However, the temperature characteristics of all potting materials and filter capacitors have certain influence on the environmental characteristics of power filter.
For more information about YBX EMI Filters, please visit us：https://www.emipowerfilter.com/.
Email：sales22@yanbixinkeji.com
EMI power filter selection considerations
Notes On EMI Power Filter Selection
The main performance indicators of EMI power filter generally include insertion loss, frequency characteristics, impedance matching, rated current value, insulation resistance value, leakage current, physical size and weight, use environment and its own reliability. In the use of the most considered is the rated voltage and current value, insertion loss, leakage current three.
When we choose the power filter, we should mainly consider three aspects of the indicators:
1.The voltage/power supply
Power supplies can be divided into AC power supplies and DC power supplies. Accordingly, many manufacturers of power filters can also be divided into AC and DC.
In principle, the AC power filter can be used for both AC and DC power supplies, but the DC filter can not be used for communication, mainly due to the low voltage resistance of the capacitor in the DC filter, and may have high AC loss and cause overheating. Even the voltage resistance of the DC filter is not a problem because the DC filter uses a large capacity common-mode filter capacitor if the leakage current will exceed the leakage current problem.
Therefore, DC power filters should never be used in AC situations.
Ac filter used in DC situation, from the point of view of safety is no problem, but to pay the cost and volume of the price; In the prototype phase, if you happen to have an AC filter, you can replace the DC filter.
When the working current of the power supply filter exceeds the rated current, the filter will not only be overheated, but also the low frequency filtering performance will be reduced. This is because the inductance in the filter will saturate the magnetic core and reduce the actual inductance in the case of a large current. Therefore, when determining the rated working current of the filter, the maximum working current of the equipment shall prevail to ensure that the filter has good performance under the maximum current state. Otherwise, when the interference appears under the maximum working current state, the equipment will be interfered or the conduction emission will exceed the standard.
When determining the rated current of the filter, a certain margin should be left; In particular, it is customary for people to call the AC "effective value", rather than the AC "peak", leaving a certain margin is very necessary. The rated current value of the general filter should be 1.5 times the actual current value.
2.Followed by insertion loss
From the point of view of interference suppression, insertion loss is the most important index. ? The insertion loss is divided into differential mode insertion loss and common mode insertion loss.
How to use the power filter to determine the required insertion loss?
Firstly, the filter is not installed at the power supply entrance of the equipment, and the conduction emission and conduction sensitivity of the equipment are measured, and compared with the standards to be met, to see how much difference between the two decibels. The role of the filter is to make up for this gap.
3.The last is the structure size
Since the inside of the filter is generally potting, environmental characteristics are not the main problem. However, the temperature characteristics of all potting materials and filter capacitors have certain influence on the environmental characteristics of power filter.
For more information about YBX EMI Filters, please visit us：https://www.emipowerfilter.com/.
Email：sales22@yanbixinkeji.com
How to Select an EMI Power Filter?
Switch-mode power supplies are inherently noisy with respect to electromagnetic emissions (EMI). The fast switching of high voltage and current nodes leads to relatively large di/dt and dv/dt values within the circuit causing noise to be emitted across a wide frequency range. Regulatory bodies in most countries set limits on the amount of electromagnetic noise that may be emitted. As a result, a lot of time and effort is given to mitigating noise sources and filtering out any noise that remains. However, while these power supplies will comply with regulations when tested alone, adding them to a system can lead to unintended electromagnetic emissions, which will require extra filtering to obtain regulatory approval. Off-the-shelf EMI filters, if properly selected, are an easy way to improve the emissions and comply with regulations.
EMI and Electromagnetic Compatibility Background
When dealing with electromagnetic compatibility (EMC), the problem is commonly modeled with three components: sources, paths, and receptors.
The sources are those devices or circuit nodes that produce the interference. In addition to the power supply itself, this may include other devices such as microprocessors, video drivers, RF generators, etc.
Noise generated by a source has two paths it can then travel. The first is a radiated path, which is electromagnetic energy propagating out into space and coupling into other systems. The second is a conducted path where the signal travels through the conductors of the system (e.g. PCB traces and planes, component leads, input wiring, etc.). This can get back into the mains power lines and affect other equipment being powered from that line.
Receptors are those devices which pick up noise emitted by the source and are affected by the interference. Receptors can include just about every analog and digital circuit.
When testing for EMC, the regulator will test conducted and radiated electromagnetic emissions separately. Each has its own limits and frequency range along with its own suppression method. Radiated emissions cover a higher frequency range (typically 30 MHz to 1,000 MHz) and as the noise travels through space it is limited in how it can be controlled. Besides using proper layout and circuit design techniques to attenuate the noise at the source, shielding can be used to contain the radiated noise. On the other hand, conducted emissions cover a lower frequency range (typically 0.15 MHz to 30 MHz), and, because they travel through conductors, can be controlled using electrical filtering components. The designer, when adding EMI filtering may choose to design it discretely or choose to go with an off-the-shelf EMI filter.
EMI Filters and System Requirements
For the engineers that choose an off-the-shelf EMI filter, there may be some confusion over how to choose the right filter for their system. The first step is making sure that the EMI filter meets the basic electrical requirements. Important items to review include:
Rated voltage, which is the maximum voltage that can be applied to the input. Exceeding this can damage components inside the filter.
Isolation voltage, which is the isolation rating measured between each input line and earth/chassis ground (there is no isolation between input and output).
Rated Current, which is the maximum current that can pass through the EMI filter within the specified operating temperature range.
Operating Temperature, which is the maximum temperature that the device may be operated.
Leakage Current, which is the current that flows through the earth/chassis ground. The EMI filter will contribute leakage current in addition to that of the power supply itself. Due to safety concerns leakage current has regulated limits and the contribution of leakage by the filter should be considered by the designer.
EMI Filtering Characteristics
After finding an EMI filter that meets the operating conditions of the system, the actual filtering characteristics should be reviewed. In the datasheet there will typically be insertion loss graphs, one for common mode and one for differential mode. These graphs show the user how much the signal will be attenuated between input and output with respect to frequency.
Insertion loss is the ratio of the signal at the input of the filter to the signal at the output, usually measured in decibels, due to the large frequency range covered, as shown in the following equation.
Insertion Loss (dB) = 20 Log 10 (Unfiltered signal / Filtered Signal)
This can be re-written, using the quotient rule, to solve for the filtered signal.
Filtered Signal (dB) = Unfiltered Signal (dB) - Insertion Loss (dB)
In some cases, a graph is not given and instead a noise attenuation value is listed in the datasheet. This is usually paired with a frequency range over which the attenuation is applicable. For example, a datasheet may specify 30 dB of attenuation between 150 kHz and 1 GHz.
The final item to note when reviewing the filter data is that the source and load impedances will change the filter's behavior. The insertion loss given in the datasheet was obtained using an impedance (typically 50 Ω) that may be quite different from that of the system it is being applied to. So, while a filter may look good on paper, it is important to test the filter in circuit to verify its performance under the actual source and load conditions of the end system.
EMI Filter Selection
When choosing an EMI filter, it is ideal if the power supply to be filtered has gone through preliminary EMC testing in order to get a baseline of the conducted emissions. The test results will tell a designer at what frequencies the unit failed and by how much. This information can be compared to the insertion loss graphs of the EMI filter to determine if it offers enough attenuation at the failed frequencies to pass the EMC test. For example, if the common mode emissions test failed by 64 dB at 500 kHz, referencing the EMI filter's common-mode insertion loss graph below shows at 500 kHz an attenuation level of approximately -75 dB. If this EMI filter was applied, one could expect to pass the EMC test with 11 dB of margin at 500 kHz.
Because of the inconsistent attenuation across the frequency spectrum, it is important to make sure that all failed or marginal frequencies will be properly attenuated. If the datasheet provided a single attenuation value instead of an insertion loss graph, it is crucial to make sure that this single value was greater than the largest margin of failure.
Conclusion
Switching power supplies are a major source of electromagnetic emissions (EMI), which makes their regulation vital to prevent interference with other electronics. Most, if not all, switching power supplies will have a filter at the input, but due to the wide range of applications, this may not always be enough to pass final EMC testing once applied to a complete system. Off-the-shelf EMI filters are a quick and easy way to reduce electromagnetic emissions if the internal filter is not enough and can save time over having to design a discrete solution from the ground up. CUI offers several ac-dc EMI power filters and dc-dc EMI power filters in board mount, chassis mount, and DIN rail configurations readily optimized for a system's electromagnetic compatibility needs.
How does an EMI Filter work?
Electromagnetic interference (EMI) is broadly defined as the electrical or magnetic interference that degrades or damages the integrity of a signal or the components and functionality of electrical equipment. Electromagnetic interference; which encompasses radio frequency interference, is normally broken into two broad areas:
Narrowband emissions are usually man-made and limited to a tiny area of the radio spectrum. The hum that power lines make are a good example of a narrowband emission. They may be continuous or sporadic.
Broadband emissions can be either mad-made or natural in origin. They tend to effect a large area of the electromagnetic spectrum. They can be one time events that are random, sporadic, or continuous. Everything from a lightning strike to computers generate broadband emissions.
Sources of EMI:
The electromagnetic interference that EMI filters deal with can be caused in a number of ways. Inside of an electrical device the interference can be generated by impendence opposition to current, in interconnected wiring. It can also be generated by voltage variances in conductors. EMI is produced externally by cosmic energy, such as solar flares, power or telephone lines, appliances, and power cords. A significant portion of electromagnetic interference is generated along and carried by power lines to equipment. Electromagnetic interference filters can be either devices or internal modules that are designed to reduce or eliminate these types of interference.
EMI Filters:
Without delving into the hard science, most electromagnetic interference is in the high frequency range. This simply means that if the signal was measured, as a sine wave for example, the cycles would be very close together. An EMI Filter has two types of components that work together to suppress these signals: capacitors and inductors.
Capacitors inhibit direct current, in which a significant amount of electromagnetic interference is carried into a device, while permitting alternating current to pass. Inductors are essentially tiny electromagnetics that are able to hold energy in a magnetic field as electric current is passed though it, thereby reducing total voltage. The capacitors used in EMI Filters are called shunting capacitors, which redirect current in a specific range, high frequency, away from a circuit or component. The shunting capacitor feeds the high frequency current/interference into inductors that are arranged in series. As the current passes through each inductor, the overall strength or voltage is reduced. Optimally, the inductors will reduce the interference to nothing, also called shorting to ground. EMI Filters are used in a wide variety of applications. They can be found in laboratory equipment, radio equipment, computers, and medical and Military equipment.
For more information about YBX EMI Filters, please visit us https://www.emipowerfilter.com/.
EMI Power Filter Manufacturers & Factory in China
As the best EMI Power Filter Manufacturer, factory, supplier, exporter in China since 2008, ISO9001:2015 listed, YBX provides different types of EMI filters.
A collection of research and development, production, sales as one of the high-tech enterprises.
Obtained the cUL，TUV，CQC, CE, ROSH certifications.
We became the listed company in 2016, and now we are the top 500 domestic enterprises designated suppliers.
We also can do different solutions according to the customers’ requirements in price or parameters.
Our Product
EMI Filter for Led Lights
RFI EMI Filter Switch
DC EMI Filter
EMI Filter for Power Supply
Active EMI Filter
EMI Suppression Filter
EMI Noise Filter for PCB
Medical Ac EMI Filter
EMI Line Filter
Electromagnetic Interference Filter
EMI Power Line Filter With Socket
3 Phase EMI Filter
Input EMI Filter
Single Phase EMI filter
Inline EMI filter
Low Pass EMI Filter
Our Certificates
As a professional manufacturer for EMC Filter, our factory has passed the latest ISO9001:2015, cUL, TUV, CQC, CE, ROSH certifications.
Have a Special Requirement?
Generally, we have common EMC/EMI products and raw materials in stock. For your special demand, we offer you our customization service. We accept OEM/ODM. We could print your logo or brand name on EMI body and boxes. For an accurate quotation, you need to tell us the following information:
Specification
Quantity
Warranty periods
Application
Please tell us requirements for size; safety certificate， and If you have special requirements, we can customize according to your requirements; such as size, switch, installation method, output method, etc.
No MOQ limit. But for the Max quantities, it will help you get the cheaper price. The more quantity ordered the lower price you could get.
Mostly, our guarantee periods for ourEMI Filter are 2 years, 3 Years, or 5 Years. Different guarantee periods will be with different solutions in raw materials.
Tell us your application or detailed information for your projects. We can offer you the best choice, meanwhile, our engineers can give you more suggestions under your budget.
What we can offer you.......
Best Quality
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After-sale
We have rich experience in the manufacture, design, and application of EMI Filter, and serve more than 50 customers worldwide.
We have an absolute advantage in the cost of raw materials. Under the same quality, our price is generally 10%-30% lower than the market.
We have the best shipping forwarder, available to do Shipping by Air express, sea, and even door-to-door service.
Working with the top research Labs to provide free EMI diagnostic tests and we supply you free samples for the test.
We provide a 3-5 years guarantees policy. And all costs by us will be on our account. Enough stock, new design batch orders take 15-25 days for fast delivery time.
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How does an EMI Filter work?
EMI Filter Basics - Operational Principles and Faulty Installation
How to Select an EMI Power Filter?
What is an EMI filter for power supply?
EMI Filter Basics - Operational Principles and Faulty Installation
1.1 EMI Filter Definition
The EMI filter (electromagnetic interference filter), also called RFI Filters or radio-frequency interference filters, is a filter circuit composed of a capacitor, an inductor and a resistor. Its filter circuit composed of a capacitor, inductor and resistor. A passive two-way network: One end is the power supply and the other end is the load. The principle of the EMI filter is an impedance matching network: the greater the impedance adaptation between the input and output sides of the EMI filter, the power supply and load side, the more effective the attenuation of electromagnetic interference is. The filter can effectively filter out a specific frequency or external frequency in the power line, thereby obtaining a specific frequency power signal, or eliminating the power signal after a specific frequency point. In fact, an EMI filter is an electrical device/circuit that mitigates the high-frequency electromagnetic noise present on the power and signal lines.
1.2 EMI Sources
EMI is electronic noise that interferes with electrical signals and reduces signal integrity. Every electrical or electronic device connection may become a potential source of EMI. It is generated externally by cosmic energy, such as solar flares, lightning strikes, atmospheric noise, electronic equipment, power lines and so on. A large part of it is generated along the power line and transmitted to the equipment through the power line. EMI filters are devices or internal modules designed to reduce or eliminate noise interference.
1.3 Common Mode Noise and Differential Mode Noise
Figure 1. Common Mode and Differential Mode Circuit
With this characteristic of the EMI filter, a square wave group or composite noise passing through the power supply filter can be converted into a sine wave of a specific frequency.
The noise to be suppressed by the line filter can be divided into the following two types:
1) common-mode: The same noise on two (or more) power lines can be seen as the noise of power lines to the ground.
2) differential mode: Noise between power lines.
An EMI filter will have different suppressing capabilities for common-mode noise and differential mode noise, and will generally be described by the spectrum of the frequency corresponding to the suppression (in decibels).
1.4 Why Do We Need EMI Filters?
Electromagnetic compatibility (EMC) is an important indicator to measure the quality of electronic products, and it has increasingly become the key in the design of electronic products. In the design process of the power system, the introduction of electromagnetic compatibility design can improve the overall anti-interference ability of the power system, extend the service life of the system, and ensure the safety of use. Therefore, the electromagnetic interference filter is a device that provides good electromagnetic compatibility.
Ⅱ Adaptation Principle of EMI Filters
The filter circuits commonly used in power supply filters are passive filtering and active filtering. The main forms of passive filtering are capacitor filter, inductance filter and complex filter (including inverted L-type, LC filter, LCπ-type filter and RCπ-type filter, etc.). The main form of active filter is active RC filters, also known as electronic filters. The magnitude of the pulsating component in the DC current is represented by the pulsation coefficient S. The larger the value, the worse the filtering effect.
Pulsating coefficient (S) = fundamental maximum of output voltage AC component / DC component of output voltage
The specific working principle is as follows: After the alternating current is rectified by the diode, the direction is single, but the current is still changing constantly. This pulsating DC is generally not directly used for radio power supply. Therefore, it is necessary to convert the pulsating DC into a smooth wave DC, which is filtering. In other words, the task of filtering is to reduce the fluctuation component of the rectified output voltage as much as possible and convert it into an almost constant DC power supply.
According to the electromagnetic interference characteristics of the power port, the EMI filter can transmit AC power to the power source without attenuation. This not only greatly reduces the EMI noise of AC transmission, but also effectively suppresses the EMI noise generated by the power supply, preventing them from entering the AC grid to interfere with other electronic devices.
This is a passive network structure suitable for both AC and DC power supplies and has a two-way suppression function. Inserting it between the AC power grid and the power supply is equivalent to adding a blocking barrier between the EMI noise of the AC power grid and the power supply, that is, two-way noise suppression, so it is widely used in various electronic products.
Aiming at the characteristics of electromagnetic interference from power terminals, an electromagnetic interference filter is designed. It is usually a selective two-terminal network composed of an inductor, a capacitor, a resistor or a ferrite device. According to the working principle, it is called a reflection filter. It provides high series impedance and low parallel impedance in the filter stopband, which causes it to be seriously mismatched with the impedance of the noise source and the load impedance, thereby transferring unwanted frequency components back to the noise source.
Ⅲ Operating Principles
The following figure is a typical circuit diagram of the EMI filter: C1and C2 are differential-mode capacitors, generally called X capacitors, the capacitance is often between 0.01μF and 0.47μF; Y1 and Y2 are common-mode capacitors, generally called Y capacitor, the capacitance should not be too large, generally in the tens of nanofarads, if it is too large, it will easily cause leakage; L1 is a common-mode choke, which is a pair of coils wound in the same ferrite ring in the same direction. The inductance is about a few millihenries. For the common-mode interference current, the magnetic fields generated by the two coils are in the same direction, and the common-mode chokes coil exhibits a large impedance to attenuate the interference signal. For the mode signal, the magnetic field generated by the two coils offsets, so it does not affect the performance of the circuit. It should be noted that this is a primary filter circuit, if you want better results, you can use secondary filtering.
Figure 2. Typical Circuit Diagram of An EMI Filter
To judge an EMI filter good or not, it is necessary to understand its performance indicators. The main parameters: rated voltage, rated current, leakage current, insulation resistance, withstand voltage, operating temperature, insertion loss, etc. The most important one is insertion loss. The insertion loss is often expressed by "IL", sometimes it is also called insertion attenuation. This indicator is the main indicator of the performance of the EMI filter. It is usually expressed by the decibel number or the frequency characteristic curve. It refers to the power ratio or terminal voltage ratio of the test signal from the power supply to the load before and after the filter is connected to the circuit. The larger the number of decibels, the stronger the ability to suppress interference. For example, some insertion loss can be tested with a 50-ohm test system. The following figure shows the insertion loss of an EMI filter.
Figure 3. The Insertion Loss of An EMI Filter
Ⅴ Selection
Therefore, when purchasing the EMI filter, the phase number, rated voltage, rated current, leakage current, certification, volume and shape, insertion loss, etc. should be fully considered. The rated voltage/current should meet the product requirements, and the leakage current cannot be too large. EMI filter with relevant certification system can be selected. Determine its volume and shape according to the actual application. When the insertion loss is large, the suppression ability is strong, etc.
In addition to these, there are some details needed to consider. For example, some EMI filters are military-grade and some are industrial-grade. Some are dedicated to household equipment, some are dedicated to inverters, and some are dedicated to medical equipment. Only when the object is determined can you choose a suitable one. As long as the basic conditions are met, the price is the key factor to consider.
Ⅵ Installation
1. The EMI filter cannot have an electromagnetic coupling path.
1) Power lines are too long.
2) Power lines are too close.
Both of these are incorrect installations. The point of the problem is that there is an obvious electromagnetic coupling path between the input wire of the filter and its output wire. In this way, the EMI signal present at one end of the filter escapes the suppression of the filter and is directly coupled to the other end of the filter without attenuation. Therefore, the filter input and output lines must be effectively separated first.
In addition, if the above two types of power supply filters are installed inside the shield of the device, the EMI signal on the internal circuits and components of the device will be directly coupled to the outside of the device due to the EMI signal generated by the radiation on the (power) terminal of the filter. Therefore, the device shielding loses the suppression of EMI radiation generated by internal components and circuits. Of course, if there is an EMI signal on the filter (power supply), it will also be coupled to the components and circuits inside the device due to radiation, thereby damaging the suppression of the EMI signal.
2. Don't bundle cables together.
In general, when installing an EMI filter in an electronic device or system, be careful not to bundle the wires between the power end and the load end together, because this undoubtedly aggravates the electromagnetic coupling between them to cause poor EMI signals suppression.
3. Try to avoid using long grounding wires.
It is advisable to connect the inverter or the motor to the output of the EMI filter at a length of not more than 30 cm. Because an excessively long ground line means a large grounding inductance and resistance, it can severely damage the filter's common-mode suppression. A better method is to secure the shield of the filter to the housing at the power inlet of the unit with metal screws and star spring washers.
4. The input line and output lines must be pulled apart.
Having distance does not mean parallel connection, because this will reduce the filter performance.
5. The EMI filter housing must be in good contact with the case shell.
The inverter-specific filter metal case and the case shell must be connected well, as well as the ground wires.
6. The connection lines should be twisted pair.
The input and output connection lines are preferably choosing shielded twisted pairs, which can effectively eliminate some high-frequency interference signals.
Frequently Asked Questions about EMI Filter Basics
1. What is an EMI filter?
EMI Filters, or electromagnetic interference filters, also called RFI Filters or radio-frequency interference filters, are an effective way to protect against the harmful impacts of electromagnetic interference.
2. What causes EMI?
Conducted interference
Conducted EMI is caused by the physical contact of the conductors as opposed to radiated EMI which is caused by induction (without physical contact of the conductors). For lower frequencies, EMI is caused by conduction and, for higher frequencies, by radiation.
3. What is an EMI filter used for?
Most electronics contains an EMI filter, either as a separate device, or embedded in circuit boards. Its function is to reduce high frequency electronic noise that may cause interference with other devices. Regulatory standards exist in most countries that limit the amount of noise that can emitted.
4. What is DC EMI filter?
Filter provides noise suppression in both directions protecting your DC lines from noise generating by a particular piece of equipment, or protecting your sensitive equipment from noise coming from DC power supply or other loads.
5. Where should I place my EMI filter?
A power line or mains EMI filter is placed at the power entry point of the equipment that it is being installed into to prevent noise from exiting or entering the equipment. Essentially, an EMI filter is made up of two basic types of components–capacitors and inductors.
6. What is the difference between RFI and EMI?
The terms EMI and RFI are often used interchangeably. EMI is actually any frequency of electrical noise, whereas RFI is a specific subset of electrical noise on the EMI spectrum. ... Radiated EMI is similar to an unwanted radio broadcast being emitted from the power lines.
7. How can I reduce EMI?
Use twisted pair shielded cable to carry instrumentation signals. Twisting the wires equalizes the effect of EMI on both wires, greatly reducing error due to EMI. Surrounding the instrument wires with a shield protects them from EMI, and provides a path for EMI-generated current to flow into ground.
8. How does EMI filter works?
EMI, or Electro-Magnetic Interference, is defined as unwanted electrical signals and can be in the form of conducted or radiated emissions. ... The capacitors provide a low impedance path to divert the high frequency noise away
Best EMC Filter Manufactures
As the best EMC Filter manufacturer, factory, supplier, exporter in China since 2008, ISO9001:2015 listed, YBX provides different types of EMC filters.
A collection of research and development, production, sales as one of the high-tech enterprises.
Obtained the cUL，TUV，CQC, CE, ROSH certifications.
We became the listed company in 2016, and now we are the top 500 domestic enterprises designated suppliers.
We also can do different solutions according to the customers’ requirements in price or parameters.
Our Product
EMI EMC FIlter
EMC Line filter
EMC Filter Led
EMC Low Pass EMI Filter
220 Volt EMC filter
EMC Power Filter
AC Line Filter EMC
EMC Filter 250v
EMC(IEC) Input Filter
AC EMC filter
EMC Noise Filter
3 Phase EMC Filter
Our Certificates
As a professional manufacturer for EMC Filter, our factory has passed the latest ISO9001:2015, cUL, TUV, CQC, CE, ROSH certifications.
Have a Special Requirement?
Generally, we have common EMC/EMI products and raw materials in stock. For your special demand, we offer you our customization service. We accept OEM/ODM. We could print your logo or brand name on EMI body and boxes. For an accurate quotation, you need to tell us the following information:
Specification
Quantity
Warranty periods
Application
Please tell us requirements for size; safety certificate， and If you have special requirements, we can customize according to your requirements; such as size, switch, installation method, output method, etc.
No MOQ limit. But for the Max quantities, it will help you get the cheaper price. The more quantity ordered the lower price you could get.
Mostly, our guarantee periods for ourEMI Filter are 2 years, 3 Years, or 5 Years. Different guarantee periods will be with different solutions in raw materials.
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EMC Filter Design
How does the EMC Filter work?
EMC Filtering For industrial Applications
EMC Filter Design - About EMC filter design foundation and abstract
The EMC filter design is critical to electromagnetic compatibility, EMC performance. The EMC filter must be capable of providing the required level of attenuation of the unwanted signals while allowing through the wanted signals. In addition to this, the EMC filter design must match both the source and load impedances.
Typically for a high impedance circuit, a capacitor connected between the line and ground provides better results, while for low impedance circuits a series inductor placed within the line provides the best results. Often a single component like this is designed to have a reactance with little effect at frequencies appropriate to the wanted signals, but a much higher effect at the higher frequencies of the unwanted signal can provide levels of attenuation of up to 30 dB or 40dB in some cases. To improve the performance of one of these basic filters, further components can be added to make multi-component EMC filters. However, to give the required performance they must be configured correctly. One precaution to ensure that inductors face a low impedance sink or source and capacitors face a high impedance.
EMC Filter Design:
In order that an item of electronic equipment can pass its EMC testing and gain its EMC compliance, it is necessary to incorporate various elements into the design. By designing the circuit to meet the electromagnetic compatibility, EMC requirements it is possible to significantly reduce the levels of unwanted signals entering and leaving the unit. One of the major ways in which this can be done is to use an EMC filter or a series of filters.
There are many ways in which EMC filters can be incorporated into a unit from a mechanical viewpoint. They may exist as stand-alone EMC filters to be fixed near to the extremities of the unit. They may be mounted on the edge of the electronics board. However, one popular method of incorporating an EMC filter into a unit is to incorporate the filter into the connector itself. This has many advantages in terms of convenience and performance. However, whatever the method used, a filter is often necessary if the electromagnetic compatibility, EMC requirements are to be met.
EMC filter application:
When developing filters for use in electromagnetic compatibility, EMC applications, the EMC filters are nearly always low pass filters, although on occasions bandpass filters may be used. The reason for using low pass filters is that typically interfering signals, i.e. ones that are easier to pick up or radiate tend to be at higher frequencies. These can be filtered by allowing the low frequencies through and rejecting the high frequencies.
The cut-off point for the low pass filter used as the EMC filter has to be chosen so that it rejects the unwanted frequencies, but does not have any undue effect on the wanted signal. Unfortunately, this choice is not always easy and it may require some degradation of the wanted signal.
The EMC filter placing is of importance. EMC filtering can be placed at any or every level of assembly between segregated areas of circuitry.
EMC filters may be placed between segregated areas of a printed circuit board. They may be placed between different boards within a module or subassembly, and an EMC filter may be placed between different modules or subassemblies. However, a particularly important place for EMC filters is between the equipment and its external environment. An EMC filter placed here is particularly effective as it will prevent unwanted signals from even entering the equipment. Once they enter they are more difficult to contain.
EMC filter methodology:
Although circuits may be well screened to prevent any signal radiated or being picked up by the circuit itself, there are always interconnections to and from the electronics circuit. These wires themselves can conduct unwanted signals into and out of the unit. If the unit is to be able to meet its electromagnetic compatibility, EMC requirements and pass its EMC testing, it is necessary to reduce the levels of unwanted signals that can enter or leave the unit via its interconnections.
In order to enable the unwanted signals to be removed, EMC filters need to be placed in the various lines. The idea is that the interfering signals generally have a frequency above that of the signals normally traveling along the wire or line. By having what is termed a low pass filter as the EMC filter, only the low-frequency signals are allowed to pass, and the high-frequency interference signals are removed.
These EMC filters can be in one a variety of formats. Often they may be as simple as a resistor or a ferrite placed around a wire or cable. For more exacting requirements, these EMC filters may need to be made up of a number of components.
The EMC filters may be categorized into two main types. One is where the unwanted energy is absorbed by the EMC filter. The other type of filter rejects the unwanted signal and in this case, it is reflected back along the line. For EMC filtering applications, the absorptive type is preferred.
How does the EMC Filter work? | YBX
Interference Sources
Typical sources of interference are, for example, IGBT inverters for motor control and switching power supplies. Both devices generate voltages and currents with steep edges in their operation. The interference spectrum covers the entire range of 0.15 to 30MHz where the conducted emissions is measured and 30 to 1000MHz where radiated emission is measured.
Common (Asymmetrical) Interference Mode
For higher frequencies, above 1MHz, the parasitic capacities in the source of interference and the disturbed equipment also produce an interference current in the earth circuit. This common-mode interference current flows towards the disturbed equipment along both connecting lines and returns to the interference source through the earth.
Differential (Symmetrical) Interference Mode
For low frequencies, in hundreds of kHz, the interference is spread the same way as the power supply voltage. Current flows in the loop formed by the L and N conductors.
Typical EMC Filter
Common Mode Choke
Common mode choke has two windings on the same core. Coupling coefficient between L1 and L2 is k=M/(L1*L2)^0,5, where M is the mutual inductance between L1 and L2. In ideal case, L1=L2 and k=L/M
During normal operation and in differential interference mode magnetic flux generated by current through L1 is compensated by current flowing through L2 in the opposite direction. In this case, L1=L2=0.5*LDM=L-M. For typical toroid common mode choke M approaches to L and LDM~1%L
In common interference mode currents flow through L1 and L2 in the same direction, L1=L2=LCM=L+M
Filter Insertion Loss measurement
The insertion loss is a measure of the efficiency of filter. The test procedure used to measure insertion loss was updated in the IEC publication CISPR 17 in 2011 and was published as the EN 55017 standard. Generator output impedance Z0 and filter load Z2 is 50 Ohm.
Filter insertion loss depends on output impedance of interference source and load impedance. In the practice, interference source output impedance is not known and filter load impedance is not 50 Ohm. Therefore, the insertion loss graphs published in the datasheet can only be used to compare the filters to each other. It is not possible to estimate the filter attenuation in the real situation by using these graphs.
In order to better characterize attenuation in the differential interference mode, IEC CISPR 17 proposes to measure a filter with an interference source impedance of 0.1Ohm and a load impedance of 100Ohm and vice versa. This method of measurement approximates the worst case.
It is clear from the FMAB NEO 5500.2637.01 insertion loss graph that the differential mode interference suppression may be in the worst case 20 to 30 dB lower. The graph also shows that for the frequency range 20 to 50 kHz, the attenuation is negative. If some harmonic component disturbance falls into this band, it will not be suppressed but amplified!
Conclusion
For the estimation of attenuation for frequencies up to 1MHz (differential mode), it is advisable to consider 0.1/100 Ohm graph. Above the 1MHz frequency, the common mode interference prevails and the 50 Ohm graph approximates the actual EMC filter loss.
For further information about EMC, products, please do not hesitate to contact us at alisa@ybx-emc.com.
EMC Filtering For industrial Applications
EMC (Electromagnetic Compatibility) filters are used to ensure that electrical and electronic equipment does not generate, or is not affected by, electromagnetic disturbance.
Most territories apply standards to the equipment that can be sold that include requirements to limit emissions of radio frequency interference (RFI) or susceptibility to incoming RFI. In Europe, we have (EMC) Directive 2014/30/EU and in North America, they have FCC Part 15, military applications have MIL specs to name 3. EMC filters are very often needed to specifically help meet the conducted immunity and emissions.
EMC filters are produced using deceptively simple combinations of inductors, capacitors, and resistors. “Deceptively” because the way that the components can be combined to achieve the necessary real-world performance is a delicate balance between safety, physical size, cost, and manufacturability. Because of the near-infinite possible combinations of components, there are as many unique performance characteristics as there are filter products available to buy. For any particular application/standard combination, there will be many different filter products that work however there will be many others that do not. As higher performance is produced by the use of larger, more numerous, or more expensive components there will be many filter options that achieve a pass but at an unnecessarily high cost.
For this reason, YBX EMC offers a pre-compliance test service. Conducted emissions test equipment is portable so this can be carried out at our laboratory in Scunthorpe or onsite with the customer. The first stage of the process is to ask the customer to fill out a single-page questionnaire. This asks for technical details relating to the operation and connection of the equipment to be tested. Also required are details of the applicable standard and, if appropriate, which limit lines from within that standard should be applied. This information is then reviewed by an engineer firstly to determine that we have the required equipment and secondly to produce an estimated test time – and therefore price.
The equipment will then be tested with no filtering to determine if indeed a filter is needed. If a failure is detected the most appropriately rated filter with the minimum performance will then be tried. If there is still fail then the next performance level up is tested and so on. The aim is to find the product that just produces a pass with a small but significant margin to ensure that the pass can be replicated on other test setups which will have minor differences.
YBX EMC engineers are happy to modify filters to create variants that are ideally suited to the application. They can also advise on other aspects of the design and construction of the equipment which will make a pass easier (and lower cost) to obtain.
After the test, a full report can be provided. Manufacturers who are applying a self-certified CE mark can use the report as part of their technical file to demonstrate due diligence. Manufacturers who are using a notified body to provide third-party safety certification can then engage the notified body safely in the knowledge that their equipment already passes.
Changing the EMC filter used should be approached with caution. The components and insertion loss curves can be compared to give a good idea of which filters will function similarly but in the real world small differences in specification can change a pass to fail so it is best to carry out a new test when a new filter is to be used.
These, often unpredictable, real-world effects coupled with the unique circumstances of each application mean that it is not possible to specify a filter that guarantees adherence to a particular standard. There is some potential comfort in using a very high-performance filter but even one over specified filter could cost more in the long run over a test in the YBX EMC pre-compliance lab and equally as important, may still not achieve a pass unless installed correctly.
What is EMI/RFI filter?
EMI filter also called RFI filter is an electrical device/circuit. Can reduce the high-frequency electromagnetic noise on a power line and signal line. This noise is typically in the 9KHz to 10GHz frequency range. And it can degrade or prevent the signal transmissions and/or the intended performance of electrical/electronic equipment. The lower frequency components of the EM noise can impact the power quality as well.
The high-frequency noise is generated by a variety of electrical and electronic devices such as electronic controls, motors, power supplies, clock circuits, inverters, appliances, microprocessors, electronic devices, etc.
3 Phase EMI Filter
Single Phase RFI Filter
EMI Power Filter
EMI/RFI Filter Applications:
Our selection of EMI/RFI power line filters includes single-phase filters and three-phase filters in an assortment of styles and configurations to meet your specific requirements.
Our EMI/RFI filters are assembled, designed, and tested to ensure the best quality and performance for any power line application, including:
Linear power supplies
Medical directive
Modems
Systems with switching power supplies
Surge protection
Hard-disk systems
SMPS with on-board filter
Microprocessors
Computers
Machinery directive
Digital test equipment
Data terminals
Transient suppression
Process control equipment
YBX unmatched design capabilities, innovative solutions, and dedication to customer satisfaction guarantee the highest quality EMI filters for your needs. Our RFI/EMI filters are the best choice for superior power line filter safety, design, and performance.
What is EMI/RFI?
EMI (Electromagnetic Interference) is also called RFI (Radio Frequency Interference). EMI and RFI are the radiation or conduction of radiofrequency energy (or unwanted electronic noise) produced by electrical and electronic devices at levels. That interferes with the operation of adjacent equipment. Frequency ranges of most concern are 10kHz to 30MHz (conducted) and 30MHz to 1GHz (radiated).
Although the terms EMI and RFI are often used interchangeably. EMI is actually any frequency of electrical noise, whereas RFI is a specific subset of electrical noise on the EMI spectrum.
What Causes EMI/RFI?
The most common sources include components such as switching power supplies, relays, motors and tracks. These devices are found in a wide variety of equipment used in industrial, medical, white goods, and building HVAC equipment.
What are the Types of EMI | RFI?
Conducted RFI is released from components and equipment through the power line cord into the AC power line network. This conducted RFI can affect the performance of other devices on the same network.
An Electrical or Electronic Device Emits RFI in Two Ways: Radiated RFI is emitted directly into the environment from the equipment itself.
What are the effects of EMI/RFI on your electrical system?
If you are occasionally experiencing interference with your telephone system, flickering computer monitors, reliability issues with computer networks, instrumentation errors, or misbehaving electronics you are most likely experiencing EMI/RFI in your electrical environment. EMI/RFI can wreak havoc with your electronics, computers, and telephones, making your workplace difficult to work in. Since most machines have control electronic circuits, they may become difficult to control or unreliable.
How do you reduce the effects of EMI/RFI?
Depending on your application, there are many ways to reduce the effects of EMI/RFI. For conducted EMI/RFI, you can choose from a large range of EMI/RFI filters.
What are the Circuit Configurations of EMI | RFI Filters?
Typical types of EMI | RFI filters are designed for a specific type of signal and the devices in which they will be installed. The wide variation in devices and equipment that benefit from EMI filtering necessitates a range of standard solutions, as well as an expanse of customization capabilities. The following are a few types of EMI | RFI Filters.
Three-Phase Filters
Three-phase filters are similar to single-phase filters except that the filter is designed to filter three signal/power lines for three-phase power and motor systems. There are some three-phase filters that also include filtering on the neutral line for applications that require it. Three-phase filters are useful as main input filters for industrial equipment, machine tools, machinery and automation systems. Depending on the leakage performance of a filter, they may even be used with some medical devices and equipment.
Single-Phase Filters
A single-phase EMI | RFI power line filter is designed for AC or DC power lines with a positive or negative, or dual, signal/power path. This type of filter is installed in line with the power/signal lines, allowing DC and AC signals to pass without attenuation, while heavily attenuating signals from 10kHz to 30MHz. These types of filters are used in single-phase motor drives, power supplies, office equipment, and test and measurement equipment, amongst other applications. Some single-phase filters are optimized for specific applications, such as their DC performance, medical equipment requirements, industrial safety requirements, and other standards.
DC Filters
DC filters are designed specifically for filtering DC power and control lines. This could be for protecting solar panels, photovoltaic charging/converting systems, battery charging and conditioning systems, DC motor drives and inverter/converters. Though similar to AC EMI | RFI filters, DC EMI | RFI filters are optimized for passing only DC signals and are typically rated for higher DC voltages and currents. These filters are useful in preventing premature aging and protection of solar panels due to conducted emissions, such as HF stray and leakage currents.
Consisting of a multiple-port network of passive components arranged as a dual low-pass filter, the EMI/RFI filter attenuates radiofrequency energy to acceptable levels, while permitting the power frequency current to pass through with little or no attenuation. Their function, essentially, is to trap noise and to prevent it from entering or leaving your equipment. Selection of the most suitable EMI/RFI power line filter can best be based on the type of power supply or the input impedance of the equipment and the mode of the offending EMI/RFI noise.
How to Choose an EMI Filter?
Switching mode power supplies are bound to emit noise when they encounter electromagnetic emissions (EMI). The fast switching of high voltage and current nodes leads to relatively large di/dt and dv/dt values within the circuit causing noise to be emitted across a wide frequency range. Regulatory bodies in most countries set limits on the amount of electromagnetic noise that may be emitted. As a result, a lot of time and effort is given to mitigating noise sources and filtering out any noise that remains.
However, while these power supplies will comply with regulations when tested alone, adding them to a system can lead to unintended electromagnetic emissions, which will require extra filtering to obtain regulatory approval. Off-the-shelf EMI filters, if properly selected, are an easy way to improve the emissions and comply with regulations.
EMI and EMC Background
When dealing with electromagnetic compatibility (EMC) issues, they are typically modeled through three components: noise sources, paths, and receptors.
The noise source is the device or circuit node that generates the interference. In addition to the power supply itself, the noise source may include other devices such as microprocessors, video drivers, and RF generators.
Noise generated by a noise source can then be transmitted through two paths. The first is the radiation path, whereby electromagnetic energy is propagated into space and connected to other systems. The second is the conduction path, whereby the signal passes through the conductors of the system (e.g. PCB alignments and levels, component leads, input wiring, etc.). This path can return to the main power line and affect other devices that receive power from that line.
The receptor is the device that receives the noise from the noise source and is affected by the interference. Receptors can include almost all analog and digital circuits.
When testing EMC, regulators will test separately for conducted and radiated electromagnetic emissions. Each type of radiation has its own limits and frequency ranges as well as methods of suppression. Radiated electromagnetic emissions cover a much higher frequency range (typically 30 MHz to 1,000 MHz) and may be limited in how they can be controlled as noise propagates through space. In addition to using appropriate layout and circuit design techniques to attenuate noise at the noise source, shielding can be used to suppress radiated noise. Conducted electromagnetic emissions, on the other hand, cover a lower frequency range (typically 0.15 Mhz to 30 Mhz), and because they pass.
EMI Filters and System Requirements
Engineers who choose off-the-shelf EMI filters may have some confusion on how to select the correct filter for their system. The first step is to ensure that the EMI filter meets the basic electrical requirements. Important items to review include.
Leakage current, which is the current flowing through the ground/rack ground. In addition to the leakage current from the power supply itself, the EMI filter also generates leakage current. For safety reasons, the leakage current has regulatory limits and the designer should consider the effects of filter leakage.
Current rating, which is the maximum current through the EMI filter in the specified operating temperature range. Operating temperature, which is the maximum temperature at which the device can operate.
Isolation voltage, which is the isolation rating measured between each input line and ground/rack ground (no isolation between input and output).
Rated voltage, is the maximum voltage that can be applied to the input. Exceeding this value will damage the components inside.
EMI Filter Characteristics
After finding an EMI filter that meets the system's operating conditions, the actual filtering characteristics should be reviewed. The data sheet will typically have insertion loss graphs, one showing common mode loss and one showing differential mode loss. These charts show the user how much the signal frequency is attenuated between the input and output.
Insertion loss is the ratio of the signal between the filter input and output due to the large frequency range covered, usually measured in decibels and expressed as the following equation.
Insertion loss (dB) = 20Log 10 (unfiltered signal/filtered signal)
The equation can be rewritten to solve for the filtered signal using the division rule.
Filtered signal (dB) = Unfiltered signal (dB)-Insertion loss (dB)
—— common mode ------ differential mode
（1A）
(2A)
(3A)
Sometimes a graph is not given, but rather the noise attenuation value is listed in a data table. This usually matches the frequency range to which the attenuation applies. For example, the datasheet might specify 30 dB of attenuation between 150 kHz and 1 GHz.
A final item to note when viewing filter data is that the noise source and load impedance can change the behavior of the filter. The insertion loss given in the data-sheet is derived using an impedance (typically 50 Ω) that may be very different from the impedance of the system to which it is applied. So, the filter shown in the datasheet may look good, but it is important to test the filter in the circuit to verify its performance under the actual noise source and load conditions of the end system.
EMI Filter Selection
When selecting an EMI filter, it is best to perform preliminary EMC tests for the power supply to be filtered to obtain a baseline value for conducted emissions. The test results will tell the designer the frequency of failure and the degree of failure of the equipment. This information can be compared with the insertion loss graph of the EMI filter to determine whether it can provide sufficient attenuation at the failure frequency to help pass the EMC test. For example, referring to the common-mode insertion loss graph of the EMI filter below, which shows an attenuation level of approximately -75 dB at 500 kHz, determine whether a common mode radiation test yielding a value of 64 dB at 500 kHz indicates a test failure. If this EMI filter is applied, it is expected to pass the EMC test with a margin of 11 dB at 500 kHz.
Because of the inconsistent attenuation across the spectrum, it is important to ensure that all fault or margin frequencies are properly attenuated. If the data sheet provides a single attenuation value rather than an insertion loss graph, it is important to ensure that this single value is greater than the maximum fault margin.
Conclusion
Switching power supplies are a major source of electromagnetic radiation (EMI), so their regulation is key to preventing interference with other electronic devices. Most, if not all, switching power supplies have filters on the input side, but because they are used in a wide range of applications, they are not always guaranteed to be adequate to pass the final EMC test when used for the entire system. Off-the-shelf EMI filters are a quick and easy way to assist in reducing electromagnetic emissions when internal filters are not sufficient and are more time efficient than designing a separate solution from scratch. cUI offers a wide range of ac-dc EMI power filters and dc-dc EMI power filters in board-mount, rack-mount, and DIN-rail configurations that can be optimized for the EMC needs of the system.
EMI Filter Basics - A Comprehensive Guide
EMI Filters, or electromagnetic interference filters. Also called RFI Filters or radio-frequency interference filters. are Electronic devices. Electronic devices play a vital role in nearly every industry. From hospitals to industrial manufacturing, to the military. Specific devices rely on uninterrupted and dependable electricity to operate correctly. But, as more and more electronic devices enter the market, they create electromagnetic interference. That can cause these devices to malfunction, crash or fail. To protect electronic devices and systems from damage, EMI Filters block adverse inferences and allow a steady flow of power.
What is the Difference Between EMI/RFI filters?
You may hear people use EMI and RFI interchangeably when referring to electromagnetic disturbances. But, EMI and RFI are not identical.
What is an RFI filter? The term, which is an acronym for radio frequency interference, refers to noise that falls on the radio frequency spectrum within the electromagnetic frequency spectrum. Meanwhile, EMI refers to any frequency of electromagnetic noise. In other words, RFI is a subset of EMI and includes only electromagnetic currents with a frequency between 3 kilohertz and 300 gigahertz. Just like EMI, RFI can be conducted or radiated and can cause a variety of problems with electronic devices.
What does an EMI filter do?
When attached to devices or circuits, EMI filters can suppress electromagnetic noise transmitted through conduction. These filters extract any unwanted current conducted through wiring or cables, while allowing desirable currents to flow freely. EMI filters that suppress noise from grid power are also called EMI power line filters.
How does an input EMI filter work?
Most electronics contain an EMI filter, either as a separate device or embedded in circuit boards. Its function is to reduce high-frequency electronic noise that may cause interference with other devices. Regulatory standards exist in most countries that limit the amount of noise that can be emitted.
EMI, or Electro-Magnetic Interference, is defined as unwanted electrical signals and can be in the form of conducted or radiated emissions. Conducted EMI is where the noise travels along the electrical conductors and radiated EMI is where the noise travels through the air as magnetic fields or radio waves.
EMI is generated from the switching of electrical current and comes from a variety of sources including electronic power supplies. Power supplies convert an input voltage into regulated and isolated (in most cases) DC voltages to run a host of electronic components. That conversion is performed at high frequencies ranging from several kHz to more than an MHz. LED lighting, computers, motor drivers, DC relays, and battery chargers all rely on power supplies to operate.
An EMI filter for a power supply normally consists of passive components, including capacitors and inductors, connected together to form LC circuits. The inductor(s) allow DC or low-frequency currents to pass through while blocking the harmful unwanted high-frequency currents. The capacitors provide a low impedance path to divert the high-frequency noise away from the input of the filter, either back into the power supply, or into the ground connection.
In addition to assisting to meet EMI regulations, the filter also has to meet safety standards. The inductor temperature rise is measured and for main operation, the minimum electrical spacing between line, neutral, and ground are controlled. This reduces the risk of fire and electrical shock. The capacitors are also individually safety certified, depending on their position in the circuit. Special “X” capacitors have to be used across the input terminals and “Y” capacitors from the AC circuit to the ground.
EMI Filter Applications
Different EMI filters can apply in various ways to most effectively protect against damage from electromagnetic noise. EMI filters block different frequencies of noise and meet varying regulations in different industries. Here are a few types of EMI filters in residential and industrial applications.
Medical-grade EMI filters: Medical-grade EMI filters meet current requirements for medical applications and protect sensitive medical equipment from damage. EMI filters for MRI rooms are purpose-built to create a secure test chamber free of EMI from lighting, intercoms and other sources of outside noise. Effective and reliable EMI filters for medical applications can be life-saving protection against electromagnetic noise interference.
Single-phase EMI filters: Single-phase EMI filters are effective for smaller equipment, such as home appliances and electronics, as well as industrial applications, such as food service equipment, power supplies, and telecommunications. Single-phase EMI filters can also be compatible with fitness equipment and motor controls.
Three-phase EMI filters: For more stringent EMI suppression, three-phase EMI filters can block higher levels of noise through a three-stage filtering system. Three-phase EMI filters are for use in high-power applications such as industrial machinery and motors, medical equipment, test equipment and industrial tools.
Appliances and washing machines: White goods EMI filters suppress electromagnetic noise for a variety of home appliances from washing machines to treadmills. These filters ensure devices meet electromagnetic compatibility regulations and help protect them from EMI damage that can impact their performance.
Military: EMI filters for military applications specifically meet regulations and compliance standards for EMC of military devices. These reliable EMI filters protect against damage to aerospace and military communication systems for secure operations. EMI filters designed for HEMP protection are also available to protect against EMI threats.
Depending on the desired application, the impact of EMI filters can include shutting out undesirable electromagnetic noise and protecting devices and electrical systems from damage.
Finally, Yanbixin is an EMI Industry Leader
If you need effective protection against electromagnetic interference, Yanbixin can provide durable and dependable EMI filters for every application. Our inventory includes reliable EMI filters for specialized applications in the military and medical fields, as well as cost-effective EMI filters for residential and industrial use. For applications that require a custom solution, our expert team can design an EMI filter that meets your specific requirements.
With more than 14 years of experience, Yanbixin is a trusted manufacturer of high-quality EMI filters for medical, military, commercial, and residential applications. We design all our EMI filters to meet industry standards and comply with EMC regulations. Explore our selection of EMI filters or submit a custom quote request for the perfect EMI filter for your needs. For more information about custom and standard EMI filters from Yanbixin, contact us.
EMC Filter Design
What is an EMC filter？EMC filter, also known as "electromagnetic compatibility filter". EMC filters reduce the transfer of electromagnetic noise between the drive and the main power supply. It is suitable for suppressing power grid noise and high harmonics and noise and high-frequency harmonics generated by switching power supplies. High performance and price ratio and the ability to connect quickly. Higher insertion loss, low leakage current.
EMC Filter Design：
The EMC filter design is critical to electromagnetic compatibility, EMC performance. The EMC filter must be capable of providing the required level of attenuation of the unwanted signals while allowing through the wanted signals. In addition to this, the EMC filter design must match both the source and load impedances.
Typically for a high impedance circuit, a capacitor connected between the line and ground provides better results, while for low impedance circuits a series inductor placed within the line provides the best results. Often a single component like this is designed to have a resistance with little effect at frequencies appropriate to the wanted signal, but a much higher effect on the higher frequencies of the unwanted signal can provide levels of attenuation of up to 30 dB or 40 dB in some cases. To improve the performance of one of these basic filters, further components can be added to make multi-component EMC filters. However, to give the required performance they must be configured correctly. One precaution is to ensure that inductors face a low impedance sink or source and capacitors face a high impedance.
EMC Filter Purpose：
When developing filters for use in electromagnetic compatibility, EMC applications, the EMC filters are nearly always low pass filters, although on occasions bandpass filters may be used. The reason for using low pass filters is that typically interfering signals, i.e. ones that are easier to pick up or radiate tend to be at higher frequencies. These can be filtered by allowing the low frequencies through and rejecting the high frequencies.
The cutoff point for the low pass filter used as the EMC filter has to be chosen so that it rejects the unwanted frequencies, but does not have any undue effect on the wanted signal. Unfortunately, this choice is not always easy and it may require some degradation of the wanted signal.
The EMC filter, placing is of importance. EMC filtering can be placed at any or every level of assembly between segregated areas of circuitry. EMC filters may be placed between segregated areas of a printed circuit board. They may be placed between different boards within a module or subassembly, and an EMC filter may be placed between different modules or subassemblies. However, a particularly important place for EMC filters is between the equipment and its external environment. An EMC filter placed here is particularly effective as it will prevent unwanted signals from even entering the equipment. Once they enter they are more difficult to contain.
EMC Filter Methodology：
Although circuits may be well screened to prevent any signal radiated or being picked up by the circuit itself, there are always interconnections and from the electronic circuit. These wires themselves can conduct unwanted signals into and out of the unit. If the unit is to be able to meet its electromagnetic compatibility, EMC requirements and pass its EMC testing, it is necessary to reduce the levels of unwanted signals that can enter or leave the unit via its interconnections.
In order to enable the unwanted signals to be removed, EMC filters need to be placed in the various lines. The idea is that the interfering signals generally have a frequency above that of the signals normally traveling along the wire or line. By having what is termed a low pass filter as the EMC filter, only the low-frequency signals are allowed to pass, and the high-frequency interference signals are removed.
These EMC filters can be in one a variety of formats. Often they may be as simple as a resistor or a ferrite placed around a wire or cable. For more exacting requirements, these EMC filters may need to be made up of a number of components.
The EMC filters may be categorized into two main types. One is where the unwanted energy is absorbed by the EMC filter. The other type of filter rejects the unwanted signal and in this case, it is reflected back along the line. For EMC filtering applications, the absorptive type is preferred.
