Advanced EMI filters keep brush DC motors “low cost”

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.

Inexpensive and easy to operate, brush DC motors provide the ideal balance of performance at the right price in industries such as automotive, aerospace, medical, industrial, appliance, consumer and home automation products. As a result, billions are manufactured annually worldwide, a figure that is expected to increase over the next 10 years.

However, increasing electromagnetic compatibility (EMC) requirements along with more crowded and “noisy” electronic environments are threatening to upset the balance by driving the cost of these low-end solutions to a level on par with more expensive brushless alternatives.

The issue is the electromagnetic interference (EMI) generated by the brushes as they rub the commutator – an inherent drawback of the design. To counteract the noise generated, a combination of shielding and filtering components is required.

This not only drives up the cost, but many EMI/RF filtering solutions for brush DC motors on the market are not satisfactory to meet today’s higher EMC requirements. In fact, many EMI filtering solutions do not filter out all forms of noise that are generated and many cannot handle higher DC currents without a corresponding escalation of the cost.

To address these concerns, more advanced EMI filtering solutions are entering the market that increase costs of brush DC motors slightly, while meeting the evolving EMC requirements.

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