DC Machines

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 …

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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 …

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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 …

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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. …

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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 …

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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 …

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Swinburne’s Test

Swinburne’s Test is an indirect method of testing of DC machines. In this method, the losses are measured separately and the efficiency at any desired load is predetermined. Machines are tested for finding out losses, efficiency and temperature rise. For small machines direct loading test is performed. For large shunt machines, indirect methods are used …

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