What is Electric Traction and how is it useful for Vehicles

What is Traction

Traction is the act of drawing or pulling, by an elastic or spring force. It refers to a maximum frictional force that can be produced by a surface without slipping

Traction is the result of specific friction coefficient for example in vehicles the traction is created between the rubber and ground

Why traction is needed

If we walk into a surface without good grip our legs and feet could not move us forward and it is same for the vehicles if the ground does not provide enough resistance or traction, the generated force from the engine won’t be able to move the car If there is more traction then more torque can be generated to move more weight

Types of a Traction system

• Non-electric traction system– this system does not use electricity at any stage example steam engine drive, internal combustion drive

• Electric traction system – if electric supply is used to drive a locomotive that system is called as electric traction

Examples are battery electric drive, diesel electric drive

Types of Electric traction

Electric traction is subdivided into

• A system which operates with DC such as trolley, buses, tramways, and railways

• A system which operates with AC such as railways

This system has self-contained locomotives they could generate their own power

Diesel-electric traction

A diesel-electric locomotive uses a diesel engine to drive the electric generator which will then supplies current to traction motors, which will then be geared to the locomotive wheels

What are the requirements for a traction system

• The starting tractive force should be high to have rapid acceleration

• The track wear should be minimum

• This equipment must be capable to withstand large temporary loads

• It must be pollution-free

• Speed control should be easy

• Maintenance and initial cost must be low

• The system should be self-contain

Advantages of Electric traction

• High starting torque

• Less maintenance cost

• It is the cheapest method of traction

• Quick acceleration and braking

• Less vibration

• It is free from smoke and flue gases

Disadvantages of electric traction

• High capital cost

• Supply failure problem

• The vehicle which is operated electrically have to move on guided tracks only

• To achieve electric braking and control additional equipment are needed

What is a traction motor

The traction motor is an electric motor which provides the primary rotational torque of a machine, mostly for conversion into linear motion, it is mostly used in electrically powered rail vehicles such as electric multiple units and electric locomotives

What is a SEPEX

It is expanded as separate excitement of traction motors, in which the armature and field coils of an electric motor are fed with the independently controlled current. It also controls a degree of automatic wheel slip control during acceleration