"Steering" Problem Of DC And Pulse Current Traction Electric Locomotive

In order to solve the "steering" problem of DC and pulse current traction motors, some countries have been using thyristor commutatorless traction motors and three-phase AC asynchronous variable frequency traction motors, and are testing maglev high-speed underground mining locomotive powered by linear asynchronous motors.

Thyristor commutatorless traction motor is composed of a synchronous motor and a group of thyristor inverters. The commutator and carbon brush structure of DC traction motor are replaced by thyristor and rotor position detector.

This kind of motor has the advantages of DC motor without difficult "commutation" problem. But the thyristor and its control system are very complex, so the electronic components directly affect the operation reliability of the motor. The three-phase AC asynchronous variable frequency traction motor has the advantages of simple structure, reliable operation and low cost, so it is an ideal traction motor.

However, its development and application have been limited for a time due to the need of variable frequency speed regulation. In the 1960s, the development of high-power thyristor frequency converter enabled asynchronous motor to realize frequency control.

At present, many locomotives and motor cars in various countries have adopted three-phase AC asynchronous variable frequency traction motor. In Germany and Japan, the linear induction motor is used in the test maglev high-speed underground mining locomotive.

Its primary winding is laid on the ground guide rail, which is powered by the ground variable frequency power supply to generate traveling wave magnetic field. The speed of Maglev high-speed vehicle can be changed by adjusting the frequency of power supply. The secondary winding is the reaction plate, which is installed on the frame of the narrow gauge locomotive.

The interaction between the primary traveling wave magnetic field and the secondary induced current not only produces the thrust to make the narrow gauge locomotive move forward, but also produces the magnetic pull to suspend the vehicle, and plays the role of dynamic braking in the braking condition.