Phase UW Short

What does F42 mean?

An excessive current flow, indicative of a short circuit, has been detected between the drive's output terminals U and W. This typically signifies a phase-to-phase short in the motor windings or the cabling, which can cause severe damage to the motor or drive's output stage if not immediately addressed.

• Phase-to-phase short circuit within the motor windings between U and W due to insulation failure.
• Damaged motor cable insulation between the U and W conductors, causing a short circuit within the cable.
• Contamination or metallic debris across the drive's output terminals U (T1) and W (T3).
• Incorrect wiring or loose strands causing a direct connection between U and W at the motor or drive terminals.

Click steps to track your progress.

1. 1

   Disconnect motor leads U, V, W from the drive's output terminals (T1, T2, T3). Measure resistance between motor terminals U and W with a multimeter.

2. 2

   Visually inspect the motor cable conductors for phases U and W for insulation damage, pinching, or external shorting paths.

3. 3

   Inspect drive output terminals T1 and T3 for any foreign conductive material, loose wire strands, or signs of arcing.

4. 4

   Perform an insulation resistance test (megohm) between motor phase U and phase W at the motor terminals after disconnecting the cable.

5. 5

   If the motor cable is suspected, disconnect it at both ends and perform an insulation resistance test between its U and W conductors.