Monitoring method for step switches involves selecting characteristic motor torque values for identical times in two switching processes, and comparing corresponding switch torques with limits

摘要

The method involves essentially continuously measuring current, voltage and phase angle at an electric drive motor for actuating the switch during a changeover process, computing the effective power drawn by the motor and deriving the motor torque (MxPw1,..) using the specific motor characteristic. Characteristic motor torque values for two identical times in two previous switching processes are selected and stored. Corresponding values for the torque (MxSt1,..) at the switch are derived using a given relationship, monitored and compared with limits.