Motor Short-Circuit

Hva betyr -SCF ?

This fault indicates a short-circuit or ground fault has occurred at the output of the drive controller, either in the motor cables or within the motor itself. This is a critical fault that can severely damage the drive controller's output stage (IGBTs) if power is maintained. Immediate action is required to prevent component failure.

• Insulation breakdown in motor power cables (U, V, W) due to abrasion, crushing, or chemical exposure, creating a phase-to-phase or phase-to-ground short.
• Short-circuit between motor windings or a winding to the motor frame (ground fault) inside the motor stator due to winding degradation.
• Water ingress into the motor terminal box or cable glands, creating a conductive path between phases or to ground.
• Internal failure of drive output power components (e.g., IGBTs) causing a direct short at the output terminals.
• Incorrect motor connection (e.g., delta configuration for a wye-configured motor) causing excessive current and a protective short-circuit trip.

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1. 1

   Disconnect motor cables (U, V, W) from the drive output terminals (T1, T2, T3) before proceeding.

2. 2

   Perform an insulation resistance test (megger) on each motor phase cable to ground and phase-to-phase. Test at 500VDC.

3. 3

   Measure resistance between motor phases (U-V, V-W, W-U) using a multimeter at the motor terminal box. Expect balanced, low resistance readings.

4. 4

   Measure resistance from each motor phase to the motor frame ground using a multimeter. Expect an open circuit (infinite resistance).

5. 5

   If motor and cables test good, measure resistance between drive output terminals (T1, T2, T3) with power OFF. Expect high resistance (internal components).