PdMA Tip: Why is the VFD Tripping?

A few weeks ago, we discussed a possible cause of a motor tripping and any actions to take following such an event.

VFD Tripping

Today, we’re going to focus on a VFD tripping. One of the most common conversations in technical support, week in and week out, is whether the source of the problem is the motor or the drive.

Motors powered by VFDs need more testing following a trip identified by diagnostics as a stator-related anomaly. If there is damage to the phase-to-phase insulation or it is weak, the rapid voltage rise seen from many drives results in phase-to-phase currents enough to trip the VFD. The VFD gets tripped, but it does not result in lower inductance or ground wall resistance.

Determining the cause of the trip is best found by isolating and testing the insulation between phases.

Click here for a detailed application note on advanced nondestructive testing of phase-to-phase insulation, visit

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