EMI Filter Suppliers


Electromagnetic interference (EMI) filters act like water or air filters, cleaning electrical power by preventing undesirable signals from passing. Captor Corp. offers a wide range of EMI filter designs that eliminate or mitigate electromagnetic interference. Our design and fabrication solutions can overcome any EMI or radio frequency interference (RFI) challenge while meeting your specifications. We have delivered more than 10,000 custom EMI filter designs at competitive prices.

Learn how EMI/RFI filters work and the added features of a custom EMI/RFI shielding solution from Captor Corp.

How Do EMI Filters Work?

An EMI filter is present in nearly all electronics as an embedded or separate component. The EMI filter reduces high-frequency noise, a disruptive interference for electronic devices. Almost every country in the world requires some level of EMI protection in devices to limit the electronic noise devices are permitted to emit.

Electromagnetic interference is unwanted electrical signals that are either radiated or conducted emissions. Radiated EMI is noise that travels through air as radio waves or magnetic fields, while conducted EMI is noise that travels through electrical conductors.

EMI comes from various electrical sources—such as electrical power supplies—when the electrical current switches. When a power supply converts AC input voltage to isolated and regulated DC voltage, it creates a high-frequency conversion that powers the electronic device. Ranging from several kHz to over 1 MHz, the conversion results in EMI. Power supplies are present in most electronic devices, such as:

  • DC relays
  • Battery chargers
  • Computers
  • LED lighting
  • Motor drivers

A power supply’s EMI filter relies on passive components, such as inductors and capacitors, to create an LC circuit. The inductor blocks high-frequency currents that cause EMI but allows low-frequency currents through. The capacitor diverts high-frequency noise from the filter input using a low impedance path, and the noise travels to the ground connection or back to the power supply.

An EMI filter ensures that the electronic product meets EMI regulations as well as safety standards. Safety standards for EMI filters include measuring the temperature rise of the inductor and controlling the electrical spacing between ground, line, and neutral. These rules reduce the risk of electrical shock and fire. Each capacitor is certified for safety, depending on its placement in the circuit. An X capacitor can only be used across input terminals, and a Y capacitor must be used between the AC circuit and the ground.

What Features Do Captor Corp.’s Custom EMI Filters Offer?

Captor Corp. provides full in-house EMI/RFI filter design, engineering, manufacturing, and testing capabilities. We can manufacture single and multi-circuit EMI filters in L, T, Pi, or Pi with feed-through configurations. Our inductor winding and filter assembly services are completed end-to-end in our manufacturing facility.

We can design and engineer enclosures that meet the client’s specified environmental conditions, mounting specifications, space constraints, and termination needs. Our design capabilities allow us to meet various requirements, including AC voltages reaching 660 VAC and DC voltages from 1 to 5000 VDC, capacities from 0.1 to 500 amps, and continuous or intermittent duty frequencies reaching 1000 Hz.

Applications for Our Custom EMI Filters

Custom EMI filters from Captor Corp. offer optimized performance in your specific application. Whether you need EMI filters for power supplies, radios, ignition systems, generators, oscillators, or other devices, we can provide an ideal solution. Here are the main industries we serve:

  • Aerospace
  • Commercial
  • Electronics
  • Electrical
  • Military

Partner With Captor Corporation for Your EMI Filter Needs

EMI/RFI filters shield against the high-frequency interference and noise that can disrupt the function of an electronic device. The filter relies on a series of inductors and capacitors to filter interference. EMI/RFI filters must comply with safety standards and are a requirement in most countries. Captor Corp.’s EMI filters are custom-made in-house to meet your application’s dimensional and performance specifications.

Captor Corp. is a leading EMI filter company with over 55 years in the industry. We offer custom design and engineering services to create an EMI/RFI solution that meets your exact needs. We handle the entire manufacturing process in-house, from prototyping to mass production. Request a quote to learn more about our EMI filters.