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EMI Filter Basics - A Comprehensive Guide


Latest company news about 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.

emi filter

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 filter circuit

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.

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