Short Circuit
Danfoss · VLT Micro Drive FC 51
What does 16 mean?
A short circuit has been detected in the motor windings or on the motor terminals. This is a severe fault that can cause immediate and catastrophic damage to the drive's output stage if not quickly and effectively protected against, representing a major electrical failure.
Common Causes
- Direct short circuit between two output phases (U-V, V-W, U-W) or from an output phase to ground on the motor side of the drive.
- Catastrophic insulation failure within the motor windings, leading to a direct phase-to-phase or phase-to-ground short.
- Damaged or faulty motor contactor (if used on the output side) creating a short between its contacts.
- Foreign metallic object (e.g., loose screw, wire strand) bridging motor terminals or inside the motor terminal box.
- Output filter components (e.g., dv/dt filter, sine filter) failing internally, causing a short.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Immediately disconnect the motor cables from the drive's output terminals (U, V, W) and then power cycle the drive.
- 2
Using an ohmmeter, measure resistance between all three motor output phases (U-V, V-W, U-W) and from each phase to ground at the drive's output terminals.
- 3
Visually inspect the motor terminal box and the entire motor cable for any signs of physical damage, arcing, or foreign objects.
- 4
Measure the resistance of each motor winding (e.g., Phase U to Phase V, V to W, W to U) directly at the motor, expecting balanced low resistance values.
- 5
If an output filter or motor contactor is used, disconnect it and test the drive independently to isolate the faulty component.