The VPM is used with motors 1FE1...-_...1-.... and 2SP1 in synchronous version with EMF ofU > 800 V to 2000 V (Ueff 570 V to 1400 V) to limit the DC link voltage at the converter in the event of a fault.
If the line voltage fails at maximum motor speed or if the drive converter pulses are canceled as a result of the power failure, the synchronous motor regenerates at high voltage back into the DC link. The VPM detects a DC link voltage that is too high ( > 800 V DC) and short-circuits the three motor supply cables. The power remaining in the motor is converted to heat via the short circuit in the VPM and motor.