Which products are affected?
9300 vector 0.37…90 kW SW ≤ V6.3
What happens?
The drive controller sets a pulse inhibit and indicates an OU message although the DC bus voltage is below the OU switch-off threshold indicated in the documentation.
When does the problem occur?
Due to the regenerative energy the DC-bus voltage increases. Since the OU switch-off threshold with C0173 = 0; 1; 2 or 3 and a value of 755 V is relatively close to the brake chopper threshold (935x device) of 725 V (if the 400 V mains is selected), OU messages may occur despite the correct dimensioning and function of the brake chopper.
Possible diagnostics?
Record the MCTRL-DC-VOLT signal (DC-bus voltage) directly before the pulse inhibit caused by OU is activated. For instance, the digital MONIT-OU signal can be used as trigger signal.
Short-term measures/recommendations?
In case of applications at the 400 V mains the mains voltage setting can be increased to 480 V (C0173 = 4) if necessary. As a result, the drive controller only sets an OU message in case of a higher DC-bus voltage. However, please consider that the max. output currents are reduced when selecting a 480 V mains system. The max. permissible output currents of the drive controllers with 400 V mains / 480 V mains can be found in the documentation.
Evaluation:
This behaviour is usually detected during commissioning. In case of an operation at a 400 V mains the problem can in most cases be remedied by the workaround mentioned above. There are no short-term remedial measures in case of an operation at a 480 V mains (e. g. USA).
