Applications of Tractions Motors

Posted by Mitsubishi Electric on April 26th, 2021

A kind of electric motor, traction motors are used for the propulsion of a vehicle, in most cases, locomotives, elevators, and a variety of other vehicles. They are used to create rotational force or torque on a machine, which is then usually changed into a straight-line motion while attached to a locomotive.

Traction motors are powered by electricity and generate power that is required to rotate the wheels of a vehicle, an electric locomotive, or an electric roadway vehicle. The turning force thus produced by the motor is transmitted to the wheels via the driving gear unit and axle.

Types of Traction Motors

• Direct-current traction motors with series field windings are the oldest type of traction motors. They provide high torque at lower speeds for better acceleration and declining torque as speed increases, which is useful for propulsion. Also, the speed characteristic of the motor can be varied as per the requirements.
• A universal motor, which is essentially a DC system, works on alternating current and exhibits similar behaviour. The AC system allows efficient distribution of power down the length of a rail line, and also permits speed control with switchgears on the vehicle.
• AC induction motors and synchronous motors are simple and require low maintenance. They do not fulfil the purpose of traction motors because of their fixed speed characteristics. They only generate useful amounts of power over a narrow speed range that is determined by their construction and requires power semiconductors for a wide range of applications.

Applications of Traction Motors

Road Vehicles

Traditionally, road vehicles have used petrol and diesel powertrains with a mechanical transmission system. The development of electrical transmissions in recent years offers the advantage of regenerating the energy released during braking or idling to recharging the battery pack that can then be utilised to enhance the vehicle’s performance and overall efficiency.

Railways

Probably the most common application of traction motors is in the propulsion of locomotives. Traditionally, all locomotives used to run on series-wound DC motors, but the advent of high-power semiconductors has now made the use of AC induction motors, also called asynchronous traction motors, more practical. Traction motors used in Indian railways utilise the AC motor for better and more efficient operation. Contrary to the traction motors used in Indian railways, the popular French high-speed rail service, TGV, utilizes AC synchronous traction motors.

Dynamic Braking

Traction motors provide the option to either return the energy generated to the supply, called regenerative braking, or to dissipate the onboard resistors, called dynamic braking. Such a system helps in reducing the speed of the load, with lower friction braking to bring the load to a complete halt.

Automatic Acceleration

Drivers on electric trains were originally required to control the acceleration, which was later replaced by automatic acceleration. The motor circuit now consisted of an accelerating relay that would take care of the resistance.

Since high power levels are involved, traction motors most commonly require cooling for efficient operation. Be it any application, traction motors more often than not use one of the 3 cooling techniques, forced air, water, or a special dielectric liquid.