Advanced EMI filters keep brush DC motors “low cost”: Page 2 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.

Noisy electronics

When electronic devices receive strong electromagnetic waves, unwanted electric currents can be induced in the circuit and interfere with intended operations. EMI can even cause physical damage in operational equipment.

Exacerbating the issue are increases in operating circuit frequency, noises of higher frequencies that expand the affected frequency range and the miniaturization of electronic devices that shrinks the distance between source and victim.  

If that wasn’t enough, many electronic devices are more easily affected by noise, even with less energy, due to circuits today that operate at lower voltages.

As a result, industries such as the automotive sector are increasingly turning to brushless DC motors. With Brushless DC Motors, the commutation is done electronically. Therefore, there is significantly less noise generation (no noise generated by mechanical commutation), but the complexity and cost of implementation are increased.

So, given a choice, OEMs would prefer solutions that would maintain the relatively low price of the brush DC motors given the quantities involved.

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