General Features of Traction Motors: Mechanical Features & Electrical Features

An electric motor which is used to provide the primary rotational torque to a machine such as electric locomotives, elevators, conveyors, trolley buses and other electric vehicles etc. is described as a traction motor.

General Features of Traction Motors

The general features of the electric motors used for traction purpose are classified into two classes as −

• Mechanical Features

• Electrical Features

Mechanical Features of Traction Motors

The mechanical features of electric motors used for traction applications are listed below −

• Robustness - A traction motor must be mechanically strong and robust so that it can be capable of withstanding severe mechanical vibrations.

• Small Size - The overall dimensions of the traction motor must be minimum, especially the traction motor must have small diameter so that it can be arranged easily beneath the motor coach.

• Completely Enclosed - The traction motor should be completely enclosed type so when it is placed beneath the locomotive, the enclosure protects it against dirt, dust, mud, etc.

• Minimum Weight - The traction motor must have minimum weight so the weight of the locomotive will decrease. Consequently, the load carrying capability of the motor will increase, also it results in low energy consumption.

• High Efficiency - The traction motor should have high mechanical and electrical efficiency, i.e., it has low losses like windage losses, frictional losses, copper losses, iron losses, etc.

Electrical Features of Traction Motors

The electrical features of the electric motors used for traction purposes are given as follows −

• High Starting Torque - An electric motor which is being used as the traction motor must have high starting torque. It is required to start the motor on load during the starting conditions in urban and sub-suburban railway services.

• Easy Speed Control - The speed control of the traction motor must be simple and easy. This is required for the frequent starting and stopping of the motor in traction application.

• Can Withstand High Temperature - As the traction motor is highly subjected to the transient conditions due to frequent starting and stopping which results in temperature rise of the motor. Therefore, the traction motor should have the capability of withstanding high temperature without failure.

• High Overload Capacity - Since, the electric trains may have an overload condition at any time. Therefore, the traction motor should have the capability of handling excessive overload.

• Able to Operate in Parallel - In traction applications, a number of electric motors need to run in parallel to carry more load. Therefore, the speed-torque characteristics and current-torque characteristics of traction motors are such that the motors may share the total load almost equally.

• Electric Braking Ability - The traction motor should be able to provide easy and simple dynamic and regenerative braking so that the energy efficiency can be improved.

• Ability to Withstand Voltage Fluctuations - As the starting current of the motor is high. Therefore, the traction motor must have the capability of withstanding the fluctuations in supply voltage.

• Good Commutation - The traction motor should have the feature of good commutation so that the sparking at the brushes and commutator segments can be avoided.