Changing the connection mode of the traction motor is an economical speed regulation method. In low-speed operation, two traction motors are connected in series, and the voltage received by each motor is equal to half of the power supply voltage; in high-speed operation, two traction motors are connected in parallel, and the voltage received by each motor is equal to the power supply voltage. At the same time, a resistance is also connected as an auxiliary speed regulation.
③ Pulse (chopping) speed regulation method.
The pulse switch control circuit is connected in series in the traction motor circuit, and the pulse switch is used with its intermittent power supply performance to change the average value of the traction motor terminal voltage to achieve the purpose of speed regulation. In fact, the pulse speed regulation method is another way to change the terminal voltage of the traction motor.
(2) Change the excitation winding method
① Change the number of turns of the excitation winding.
Divide the excitation windings into two groups. When both groups of excitation windings are connected in series to the main circuit, the magnetic field strength is high and the speed of the motor decreases; when only one set of excitation windings is connected to the main circuit, the magnetic field strength is weakened and the motor speed increases.
② Change the connection mode of the excitation winding.
When the excitation windings are connected in series, the magnetic field strength is high and the speed of the motor is reduced; when the excitation windings are connected in parallel, the magnetic field strength is weakened and the motor speed is increased.
Small battery electric locomotives only use one traction motor. This method is usually used for speed regulation. Its advantages are economy and smoothness, but the speed regulation range is limited.
The above is an introduction to the working principle of the DC traction motor of the mine electric locomotive.