Technical Articles

Understanding Adjustable Speed Drive Common Mode Problems and Effective Filter Solutions

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Todd Shudarek, Principle Engineer – Many solutions to protect motors are present in the market. This paper presents data showing how three filters: a typical dV/dt filter, a dV/dt filter utilizing a triple defense core, and a common mode choke, perform in providing both common mode and differential mode filtering. The data shows that a typical dV/dt filter does not provide common mode filtering and a common mode choke does not provide differential mode filtering. Only the filter containing the triple defense core provides both common mode and differential mode filtering to protect the motor. This paper will also discuss how the various topologies lend themselves to providing the required protection.