What happens when a contactor controlled by a timer closes in a Primary Resistor Starter?

When a contactor controlled by a timer closes in a Primary Resistor Starter, the resistors that are initially connected in series with the motor are bypassed. As a result, the motor is then connected directly to the full line voltage.

This method allows for a smooth startup by initially limiting the voltage applied to the motor, thus reducing the inrush current and mechanical stress. Once the motor reaches a sufficient speed or condition—typically determined by the timer—the contactor pulls in, bypassing the resistors. This transition enables the motor to operate at its full capacity, which is beneficial for performance and efficiency during normal operational conditions.

The other options do not accurately represent what occurs when the contactor closes in this context. The motor does not shut off completely, nor is the power rerouted to a secondary supply, and it does not enter a low torque mode. Understanding this process is essential for those working with motor control systems, as it highlights the importance of the timing and sequencing in starting and operating industrial motors effectively.