What is the function of the shorting contactor for an ATS48? Is it a required component?
A shorting contactor engages when the motor is running at full speed. The starter provides proper sequencing of this contactor by the ``end of starting`` relay. When the start is completed, the shorting contactor will be commanded to close. The starter will continue to monitor the motor thermal state and provide motor overload protection. Upon a stop command, the KM3 (shorting contactor designation) contactor will open, transferring the motor current to the SCRs to allow for a controlled deceleration if desired.
The shorting contactor is not required, but there are definite advantages to using one: It extends the life of the internal electronics and SCRs due to the reduced heat effects of the current and SCR firing. It reduces the heat dissipated by the controller.