Advanced EMI filters keep brush DC motors “low cost”: Page 3 of 6

April 27, 2020 //By Christophe Cambrelin, Johanson Dielectrics
Advanced EMI filters keep brush DC motors “low cost”
Brush DC motors need to meet higher EMC requirements as electronic environments get more crowded and “noisy”. Further, EMI issues are going to become more of a problem with the higher frequencies with Bluetooth, Wi-Fi and now 5G devices. EMI filters will have to handle wider frequency ranges while allowing the appropriate signals to pass through.

EMI filtering

EMI/RFI interference is either radiated or conducted in wide frequency range from several hundred hertz to several gigahertz.

Radiated noise occurs when voltage is applied at varying levels to the wiring. To keep the radiations confined in the motor housing, several precautions should be taken by the manufacturers of Brush DC Motors. The most important is the material used for the motor housing, which should be metal, as well as a metal cap (not plastic) on top of it. When the cap is made of plastic, the user needs to cover it with a metal shield (that may be a metallized PCB).

When EMI/RFI is conducted, the noise generated travels along the electrical power leads and is then radiated. Shielding is ineffectual against conducted noise, so filtering is required with a separate device.  

Traditional common mode filtering approaches include low pass filters comprised of capacitors that pass signals with a frequency lower than a selected cutoff frequency and attenuate signals with frequencies higher than the cutoff frequency.

Among the options for OEMs are 2-capacitor differential, 3-capacitor (one X-cap and 2 Y-caps), feed-through filters, common mode chokes, LC filters, or combinations of these.

Design category: 

Vous êtes certain ?

Si vous désactivez les cookies, vous ne pouvez plus naviguer sur le site.

Vous allez être rediriger vers Google.