Overvoltage

What does 7 mean?

The DC bus voltage (VDC) has exceeded the inverter’s 'Overvoltage limit'. The inverter will switch off until VDC drops, but if it remains high for 5-10 seconds, it will trip with an alarm. This is typically caused by excessive supply voltage, or more commonly, by regenerative energy from the motor during rapid deceleration with insufficient ramp-down time.

• Excessive incoming AC line voltage (L1, L2, L3) or severe voltage spikes from the utility grid.
• Regenerative energy from the motor (e.g., rapid deceleration of high inertia load) overwhelming the drive's ability to dissipate it.
• Braking resistor fault (open circuit, incorrect resistance) or braking chopper malfunction, preventing energy dissipation.
• Deceleration ramp time (P2-01, P2-02) set too short for the application, causing rapid motor deceleration and regeneration.
• Internal fault in the drive's power circuit (e.g., IGBT failure, DC bus capacitor issue), leading to uncontrolled voltage.

Click steps to track your progress.

1. 1

   1. Measure the incoming AC line voltage (phase-to-phase) at terminals R, S, T with a True RMS voltmeter to confirm stable voltage within specifications (e.g., 480VAC +/- 10%).

2. 2

   2. Increase the deceleration ramp time (P2-01 or P2-02) by 25-50% to allow for slower dissipation of regenerative energy.

3. 3

   3. If a braking resistor is used, power off the drive and measure the actual resistance between terminals BR+ and BR- with an ohmmeter, verifying it matches the specified value in P1-30.

4. 4

   4. Inspect the braking resistor for damage (e.g., cracked ceramic, burnt coils) and ensure proper air circulation for cooling.

5. 5

   5. Monitor the drive's DC bus voltage (A01-01) during operation, particularly during deceleration phases, to pinpoint when the overvoltage occurs.

6. 6

   6. Disconnect the motor and run the drive at no load (or with a different motor if available) to determine if the fault is motor-related or drive-internal.