Output Phase Loss

What does Output Phase Loss mean?

One or more phases on the drive's output to the motor are disconnected, the motor winding is damaged, or connections are loose at the drive output terminals. This can also occur if the motor is too small (drawing less than 5% of the drive's rated current), leading to unbalanced currents and potential motor heating.

• Loose or corroded connection at the drive output terminals (U, V, W) or the motor terminal box causing an open circuit on one or more phases.
• Internal open circuit within one or more motor windings (e.g., stator winding burn-out or break).
• Motor cable insulation breakdown or conductor fracture for one phase between the drive and the motor.
• Motor impedance (Parameter E2-01) is significantly mismatched with the drive's output capability due to an undersized motor.
• Intermittent contactor or disconnect switch failure in the motor circuit, leading to an open phase during operation.

Click steps to track your progress.

1. 1

   1. De-energize the drive and verify tight connections at the drive output terminals (U, V, W) and motor terminals for all three phases.

2. 2

   2. With power off, measure the resistance of each motor winding (U-V, V-W, W-U) at the motor side of the terminal strip; confirm values are within 10% of each other and match motor specifications.

3. 3

   3. Measure the resistance of each motor cable conductor (U, V, W) from drive output to motor input to detect an open or high-resistance phase.

4. 4

   4. Verify that the motor rated current (Parameter E2-01) and motor rated voltage (Parameter E2-02) are correctly set in the drive parameters.

5. 5

   5. Check for insulation breakdown of the motor cables to ground using a megohmmeter (Megger test) if resistance measurements are inconclusive.