# What is Electric Traction and how is it useful for Vehicles **URL:** \ **Category:** Electrical\ **Created:** [August 6, 2019, 4:22am UTC](https://forumautomation.com/t/what-is-electric-traction-and-how-is-it-useful-for-vehicles/6923 "2019-08-06T04:22:58Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![ashlin](https://forumautomation.com/user_avatar/forumautomation.com/ashlin/32/3775_2.png) [@ashlin](https://forumautomation.com/u/ashlin)\ **Post date:** [August 6, 2019, 4:22am UTC](https://forumautomation.com/t/what-is-electric-traction-and-how-is-it-useful-for-vehicles/6923/1 "2019-08-06T04:22:59Z")
**What is Traction** [Traction](https://forumautomation.com/t/types-of-dc-motors-and-why-do-we-need-dc-motors/6680) 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](https://forumautomation.com/t/types-of-ac-motors-applications-and-disadvantages/5169), 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](https://forumautomation.com/t/types-of-brushed-dc-motors/4835) 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 ![image](https://cdn.forumautomation.com/original/2X/6/635751c9ecafb427711b8d78a0f19c9493f27e26.png) **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