Traction motor Transportation applications Railroad
A series-wound DC motor has a low electrical resistance. When voltage is applied to the motor, it makes a strong magnetic field inside the motor. This produces a high amount of torque, so it is good for starting a train. If more current than needed is sent to the motor, there would be too much torque and the wheels would spin. If too much current is sent to the motor, it could damage the motor. Resistors are used to limit the current when the motor starts.