Phase imbalance

What does 37 mean?

There is a significant current imbalance detected between the power units of the drive. This indicates an unequal load distribution or an issue with one of the power phases.

• Unequal incoming AC supply voltages or significant voltage sag on one phase at the drive input terminals.
• Loose or high-resistance connection on one of the motor output phases (U, V, W) at the drive or motor terminal box.
• Internal fault within one of the drive's power semiconductor modules (e.g., IGBTs) causing an imbalanced current output.
• Partial short circuit or turn-to-turn insulation breakdown in one phase of the connected motor winding.
• Damaged current sensor or feedback circuit for a specific phase within the drive's power section.

Click steps to track your progress.

1. 1

   1. Measure the incoming line-to-line voltages (L1-L2, L2-L3, L3-L1) at the drive input terminals while the drive is attempting to run, noting any voltage imbalances greater than 2%.

2. 2

   2. With the drive powered off and locked out, measure the resistance between each motor phase output terminal (U, V, W) and ground, and between each phase (U-V, V-W, W-U) to detect imbalances or shorts.

3. 3

   3. Inspect and retighten all motor output cable connections at the drive's U, V, W terminals and at the motor terminal box.

4. 4

   4. Perform an insulation resistance test (Megger test) on the motor windings relative to ground and between phases, ensuring readings are above 1 MΩ.

5. 5

   5. Temporarily disconnect the motor and measure the drive's output currents (if accessible via diagnostic menus) while running into a balanced resistive load to isolate the fault to the drive or motor.