Danfoss · VLT Micro Drive FC 51
One of the motor output phases (Phase W) is detected as missing by the drive. This usually points to a disconnected motor cable, a broken wire, or a poor connection at either the drive or motor terminals, preventing proper motor operation.
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De-energize the drive and verify 0VDC at the drive's U, V, W output terminals.
Measure continuity of the motor cable for phase W from the drive's W terminal to the motor's W terminal.
Inspect connections at drive terminal W and the motor's terminal box for phase W for looseness, corrosion, or damage.
Measure resistance of the motor windings (U-V, V-W, W-U) at the motor's terminal box, verifying they are balanced and within specification (e.g., 0.5-20 Ohms).
If motor and cable are confirmed good, measure resistance between drive output terminal W and the DC bus (+) and (-) terminals to check for IGBT integrity.