Motor Control Centres
The contactor’s contacts are closed to start the motor and opened to stop the motor. This is accomplished electromechanically, using start and stop pushbuttons, or other pilot devices wired to control the contactor.
The overload relay protects the motor by disconnecting power to the motor when an overload condition exists. Although the overload relay provides protection from overloads, it does not provide short-circuit protection for the wiring supplying power to the motor.
For this reason, a circuit breaker or fuses are also used.
In many commercial and industrial applications, quite a few electric motors are required, and it is often desirable to control some or all of the motors from a central location. The apparatus designed for this function is the motor control center (MCC).
A combination starter is a single enclosure containing the motor starter, fuses or circuit breaker, and a device for disconnecting power.
Other devices associated with the motor, such as pushbuttons and indicator lights may also be included.