Overvoltage during DC-injection braking

What does OU mean?

An overvoltage (OU) TRIP occurs if, during DC-injection braking (GSB) at high motor speeds, the residual voltage from magnetism and high speed generates an excessive motor current. This can lead to overvoltage due to the drive's attempt to reduce magnetization when the pulse inhibit (DCTRL-IMP) is too short.

• DC injection braking activated at too high a motor speed (P0-03), generating excessive back EMF that leads to DC bus overvoltage.
• Deceleration ramp time (P1-10) set too short, causing rapid regeneration and voltage increase on the DC bus.
• Braking resistor failure (e.g., open circuit) or incorrect sizing (resistance too high, power too low) preventing energy dissipation during regenerative braking.
• Insufficient mains supply impedance or short circuit capacity, causing the DC bus voltage to rise too quickly when the motor regenerates.
• Drive hardware fault in the DC bus sensing circuit or the braking chopper control.

Click steps to track your progress.

1. 1

   1. Increase the deceleration ramp time (P1-10) to allow for a slower decrease in motor speed (P0-03) and regenerative energy.

2. 2

   2. Verify the braking resistor's resistance value across its terminals using an ohmmeter against the specified value.

3. 3

   3. Check braking chopper threshold voltage (P1-20) and verify it is set appropriately for the DC bus voltage.

4. 4

   4. Reduce the maximum DC-injection braking current (C0202) to lessen the motor's braking torque and regenerative effect.

5. 5

   5. Monitor the DC bus voltage (P0-01) during deceleration to observe the peak values and identify the point of overvoltage.