Frequently Asked Questions

What is common mode current?

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The common mode voltage produced by the typical PWM drive induces common mode currents that travel through parasitic capacitances located in the cable and motor. Common mode currents flow through the bearings of the motor itself. This causes an effect known as “fluting” or “bearing currents.” As low common mode current discharges through the bearing, it melts small pits into the bearing. Over time, the bearing fails and can cause the motor moving at high speed to virtually self-destruct.