Incorporating Ferrites in Electrical Product Designs

Posted on 5/22/18 10:12 AM


In the medical equipment and information technology worlds, sometimes small details can make a big difference. When designing an electrical product that will be used in one of these applications, incorporating a ferrite onto the cable of the cord set may assist in enhancing the effectiveness of that product against electromagnetic interference.

A ferrite is a bead that reduces or helps prevent electromagnetic interference (EMI) from a device or to a device. EMI is an occurrence generated by another strong electromagnetic field or signal which affects the performance of an electrical or data circuit, adversely affecting equipment performance.

Ferrites offered by Interpower consist of permeable substances that are used to suppress unwanted EMI from entering or leaving the equipment through the power cord or cord set. They have medium permeability and high resistive impedance. Designed for suppression of signals between 30 and 300MHz, these ferrites are made mostly of nickel zinc. A combination of oxides from other metals, such as magnesium, manganese, copper, or cobalt, may also be included in the makeup.

When determining what kind of ferrite to use on the cable, there are several factors to consider: impedance range, frequency range, and size and kind of cable it will be used on.  When applying the ferrite onto the cable, Interpower recommends molding it four to six inches from the strain relief at the equipment or the IEC 60320 connector of a cord set. Interpower offers three different ferrites which can only be molded onto North American cable. There is one snap-on version which can be used on international cable and also on North American cable.

The following table shows the ferrites offered by Interpower. 

Part Number Minimum Impedance Impedance Frequency Cable Choices


25 MHz – 100 ohms

100 MHz – approx. 200 ohms

30-200 MHz

3x16AWG SJT fillerless PVC

3x14AWG SJT fillerless PVC


25 MHz – 104 ohms

100 MHz – approx. 213 ohms

30-200 MHz

3x18AWG SJT fillerless PVC


25 MHz – 137 ohms

100 MHz – approx. 250 ohms

30-200 MHz

3x18AWG SVT fillerless PVC


30-100 MHz – approx. 50 ohms

100-500 MHz – approx. 100 ohms

30-300 MHz

3x0.75mm2 PVC and rubber

3x1.00mm2 PVC and rubber

3x1.50mm2 PVC

3x18AWG PVC and rubber


Additional Resources

See the complete line of ferrites available at Interpower.

If you have questions, Interpower offers free technical support, along with value-added services. For further assistance, please see Interpower’s contact information below.

Topics: product design, EMI

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