[Explained] Electric Locomotive Traction System Block Diagram

In this article, we are going to discuss Electric Locomotive Traction System Block Diagram with a detailed explanation. We will discuss how an Electric locomotive takes power from the overhead line, how it used to operate the motor. There are mainly three types of electrification are used in electrical traction systems - 1. Direct Current (DC) Electrification System 2. Alternating Current (AC) Electrification System 3. Composite or Kando system. So here we will discuss the modern system that is Composite or Kando System.

Electric Locomotive Traction System Block Diagram

First, let's a look at the block diagram of the Electric locomotive traction system, then we will discuss each block the whole system.

Electric Locomotive Traction System Block Diagram, locomotive block diagram, railway traction system

How Electric Locomotive Traction System works?

The above block diagram represents a Composite or Kando system means the locomotive takes a single-phase power supply from the overhead line and it converts into the three-phase supply and using to operate the three-phase motor. Let's discuss each block, you will understand better.


The pantograph is a current collection system from the overhead line. The locomotive takes current from the overhead line through this pantograph. Pantographs are held up by compressed air pressure to connect with the overhead line. It also designed to collapse if it detects an obstruction and can be manually down to isolate the locomotive from the overhead line.

Circuit Breaker

It is an electrical protective device. It used to disconnect the locomotive from the main power supply coming through the pantograph when any fault occurs.

Axle Brush

Pantograph helps to connect phase or line conductor whereas axle brush helps to connect neutral conductor. We can say a locomotive takes current from the overload line through the pantograph and return that current through the axle brush.

Step Down Transformer

In a Kando system, the locomotive is supplied by 16KV or 25KV, 50 Hz single-phase supply. So the step down transformer is used to step down this high voltage. Tap changer also used with this transformer.

Main Rectifier

Rectifier is used to convert the single phase AC supply coming from the transformer into DC supply. Generally SCRs, IGBTs etc are used for this rectifier because it carries a very high current and electrical power.


In the above diagram you can see there are two Filters are used. These are the DC filter used to filter the DC output of the rectifier.

Three Phase Inverter

This single phase to three phase inverter is used to convert the DC supply (from the output of the rectifier) into three phase AC supply. This three phase AC supply is used to operate the three phase induction motor. Generally, high power carrying SCRs, IGBTs are used for this inverter circuit.

Motor Controller

Motor Controller is used to control the three phase motor such as speed, torque, acceleration, etc.

Traction Motor

Generally, the modern locomotive system use three phase asynchronous motor or induction motor. Induction motors are provides a very good speed regulation, regenerative breaking, high acceleration, etc.

Single Phase Inverter

In the locomotive system, a single phase inverter is also used which supply power to Lights, Fans, AC Sockets, cooling fans, battery charger, etc. This single phase inverter also take power from the main rectifier.

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[Explained] Electric Locomotive Traction System Block Diagram [Explained] Electric Locomotive Traction System Block Diagram Reviewed by Author on February 16, 2021 Rating: 5
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