What is the working principle of the DC traction motor of the mine electric locomotive?

2021-07-20

The traction motor is the power source of the mine electric locomotive. When the DC power supply is connected, the electrical components, parts and equipment of the electric locomotive (the overhead electric locomotive includes the track) form a current loop, which can make the traction motor rotate and produce Traction is converted from electrical energy to mechanical energy, and then through a series of controls of the controller, the electric locomotive is operated in the stages of starting, accelerating, constant speed, decelerating or electric braking. In order to ensure that the armature winding can generate large and stable electromagnetic torque after being energized, in the actual DC motor, there are many coils of the armature winding, which are distributed on the entire surface of the armature and are connected in series with each other. The excitation windings and magnetic poles of the stator are also increased from one pair into multiple pairs. A DC motor powered by a stator field winding and an armature winding in series is called a series motor.

Electric locomotives require multiple speeds during transportation, so certain measures must be taken to allow the driver to control the speed of the traction motor to achieve the purpose of obtaining multiple speeds. Therefore, the commonly used speed regulation methods of DC motors are as follows:

(1) Change the terminal voltage of the motor

① Series resistance method.

A resistor is connected in series in the traction motor circuit. When the resistance of the resistor is changed, the terminal voltage of the traction motor can be changed.

② The series-parallel method of traction motors.

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.

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