What is the purpose of a resistor bank in the Wound Rotor Motor Rotor Circuit?

The purpose of a resistor bank in the Wound Rotor Motor Rotor Circuit is to limit the starting surge of current. When a wound rotor motor starts, it experiences a high inrush current due to the low impedance of the rotor circuit at standstill. This inrush current can be significantly greater than the motor’s full-load current and may lead to excessive heat generation, potential damage to the motor windings, or trips in circuit protection devices.

By incorporating a resistor bank into the rotor circuit, the resistance can be adjusted to control the amount of current flowing through the rotor during startup. This practice helps to gradually increase the motor speed and reduces the electrical stress on the power supply system, contributing to a smoother, safer start. Once the motor reaches its operational speed, the resistors can be removed from the circuit to allow the system to function efficiently.