Overvoltage fault when the drive is idle
VFD overvoltage faults can occur when the drive is idle when high input AC voltage is present. If this VFD overvoltage fault is sporadic, something nearby is causing the AC line to fluctuate. If you study large inductive loads, see if they cause the distribution lines to change voltage. If an incorrect tap transformer is present, this can also cause an overvoltage fault by keeping the input line on the high side of the recommended voltage. This will not leave much room for voltage changes on the DC bus if this happens. The multimeter may not be able to detect input line fluctuations. If the voltage rises quickly and or sharply, the multimeter may not be able to capture the reading fast enough. An oscilloscope or voltage monitor may be required to capture voltage rises. Switching on and off can also cause large power spikes if the main input power line has a power factor correction cap. In this case, an isolation transformer or line reactor may be required at the front end of the drive to absorb power spikes.
