Motor short-circuit

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A short-circuit or grounding fault has occurred at the drive output, or significant ground leakage current is detected (especially with multiple motors). This indicates a severe electrical fault in the motor or its cabling, risking immediate damage to the drive and motor.

• Phase-to-phase short circuit within the motor windings or at the motor terminal box.
• Phase-to-ground fault in the motor cable (U, V, W) due to insulation breakdown, mechanical damage, or water ingress.
• Short circuit between output phases (U, V, W) at the drive output terminals due to incorrect wiring or conductive debris.
• Significant ground leakage current exceeding the drive's internal protection threshold (often indicates multiple motor faults or long, improperly shielded cables).
• Failed output IGBT module within the drive, causing a persistent short circuit on an output phase.

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1. 1

   1. With drive de-energized and motor cable disconnected from drive output, measure insulation resistance from each motor phase (U, V, W) to motor ground using a megohmmeter (e.g., 500VDC); acceptable > 1 MOhm.

2. 2

   2. Measure motor winding resistance across phases (U-V, V-W, W-U) with an ohmmeter; look for extremely low resistance (near 0 Ohms) or significant imbalance indicative of a short.

3. 3

   3. Inspect the motor terminal box and motor cable entries for signs of arcing, water ingress, or loose/damaged insulation.

4. 4

   4. Check the motor cable for any visible damage, pinching, or crushing along its entire length. If suspicion exists, test individual cable conductors for phase-to-phase and phase-to-ground shorts.

5. 5

   5. Isolate the motor by disconnecting it from the drive output terminals (U, V, W). If the fault clears upon attempting to run the drive without the motor, the fault is external (motor or cable).

6. 6

   6. Verify that motor cable shielding is correctly terminated at both the drive and motor ends according to EMC guidelines to minimize ground leakage currents.