# Electrical Machines

## Distribution Factor

The Distribution Factor or the Breadth Factor is defined as the ratio of the actual voltage obtained to the possible voltage if all the coils of a polar group were concentrated in a single slot. It is denoted by Kd and is given by the equation shown below. In a concentrated winding, each phase of …

## Coil Span Factor

The Coil Span Factor or Pitch Factor KC is defined as the ratio of the voltage generated in the short pitch coil to the voltage generated in the full pitch coil. The distance between the two sides of a coil is called the Coil Span or Coil Pitch Factor. It is also known as Chording Factor. …

## Synchronous Machine

Synchronous Machine constitutes of both synchronous motors as well as synchronous generators. An AC system has some advantages over a DC system. Therefore, the AC system is exclusively used for the generation, transmission, and distribution of electric power. The machine which converts mechanical power into AC electrical power is called a Synchronous Generator or Alternator. …

## 4 Point Starter

A 4 Point Starter is almost similar in functional characteristics to 3 Point Starter. In the absence of back EMF, the 4 Point Starter acts as a current limiting device while the starting of the DC motor. 4 Point Starter also acts as a protecting device. The basic difference in 4 Point Starter as compared …

## 3 Point Starter

3 Point Starter is a device whose main function is starting and maintaining the speed of the DC shunt motor. The 3 point starter connects the resistance in series with the circuit which reduces the high starting current and hence protects the machines from damage. Mainly there are three main points or terminals in 3 …

## Armature Reaction in a DC Generator

Definition: The armature reaction simply shows the effect of armature field on the main field. In other words, the armature reaction represents the impact of the armature flux on the main field flux. The armature field is produced by the armature conductors when current flows through them. And the main field is produced by the …

## Four Quadrant Operation of DC Motor

Four Quadrant Operation of any drives or DC Motor means that the machine operates in four quadrants. They are Forward Braking, Forward motoring, Reverse motoring and Reverse braking. A motor operates in two modes – Motoring and Braking. A motor drive capable of operating in both directions of rotation and of producing both motoring and …

## Hopkinson’s Test

Hopkinson’s Test is also known as Regenerative Test, Back to Back and Heat Run Test. In Hopkinson Test, two identical shunt machines are required which are coupled both mechanically and electrically in parallel. One is acting as a motor and another one as a generator. The input to the motor is given by the supply mains. …

## Electrical Braking of DC Motor

Electrical Braking is usually employed in applications to stop a unit driven by motors in an exact position or to have the speed of the driven unit suitably controlled during its deceleration. Electrical braking is used in applications where frequent, quick, accurate or emergency stops are required. Electrical Braking allows smooth stops without any inconvenience …

## Plugging or Reverse Current Braking

In Plugging or Reverse Current Braking the armature terminals or the supply polarity of a separately excited or shunt motor when running are reversed. Therefore, in plugging the supply voltage V and the induced voltage Eb which is also called back EMF will act in the same direction. Thus, during plugging the effective voltage across …