UW Short Fault

What does 42 mean?

This fault indicates that excessive current has been detected between the 'U' and 'W' output terminals of the controller. This is typically caused by a short circuit either within the motor windings themselves or in the external wiring connecting the controller to the motor. This is a critical fault that can cause immediate and severe damage to the controller's inverter section.

• Phase-to-phase short circuit between the U and W conductors in the motor cable.
• Internal short circuit between the U and W phase windings within the motor.
• Damage or foreign material on the output terminal block (U and W) of the controller, creating a conductive path.
• Insulation breakdown within the motor resulting in a direct U-W winding short.
• Sudden, severe mechanical overload causing instantaneous motor winding damage leading to a short.

Click steps to track your progress.

1. 1

   1. Immediately disconnect the motor from the controller's U, V, W output terminals.

2. 2

   2. Measure the resistance between the U and W terminals of the motor cable using an ohmmeter (cable disconnected from both controller and motor).

3. 3

   3. Measure the resistance between the U and W motor winding terminals (motor disconnected from cable) using an ohmmeter. Compare to expected motor winding resistance.

4. 4

   4. Inspect the controller's U and W output terminals and the corresponding motor cable lug connections for signs of arcing, carbon tracking, or debris.

5. 5

   5. Perform a hipot test (AC or DC) between the U and W conductors of the motor cable to confirm insulation integrity, following safety procedures.