Electrical Machines

Permanent Magnet Stepper Motor - Construction & Working

A stepper motor is an electro-mechanical device that actuates a train of step movements of a shaft in response to a train of input pulses. The step movement may be angular or linear. The step movement of the motor is according to…

Ac Series Motor - Construction & Principle of Operation

Principle of Operation of AC Series Motor : An ordinary dc series motor will run in the same direction regardless of the polarity of the supply. The direction of the torque depends upon the relative directions in space of flux a…

Cross-field Theory of Single phase Induction Motor

It is interesting to know how a single-phase induction motor can able to rotate when an initial rotation or starting torque is given to it. This can understand with the help of cross-field theory and double-revolving field theory…

Double Revolving Field Theory

When a single-phase ac supply is given to the single-phase stator winding, a sinusoidally pulsating magnetic field varying with time is produced. As the produced magnetic very two times in a cycle, therefore, no torque will be pr…

Speed Control of DC Motors - shunt & series

Industrial as well as domestic loads need speed variation. Some of the loads require to change the speed in steps and some of the motors require to change the speed uniformly. For instance, in the paper industry, while rolling th…

Torque Equation of a DC Motor

Torque or moment or moment of force is the tendency of a force to rotate or move an object about an axis. A force is a push or pull, likewise, torque is a twist to an object. Mathematically, torque, T = F × r. Let T g = armatu…

Back E.M.F of DC Motor and Equation

What is Back EMF in DC Motor : When the armature of a dc motor rotates, the windings or conductors on the armature also rotate in the magnetic field. According to "Faraday's Laws of Electro-Magnetic Induction" emf …

Parallel Operation of DC Generator - Conditions & Advantages

Conditions for Parallel Operation of Dc Generator : To connects the generators in parallel to common bus-bars, the generators should satisfy the following conditions. The incoming generator's voltage should be the same as t…

Lap and Wave Winding

Lap Winding : When the winding is connected in such a manner that the end of the one coil is connected to the starting end of other coils (adjacent coil) of the same pole and so on then the winding is known as lap winding. Lap…

Methods of Improving Commutation in DC Generator

There are two methods of improving commutation i.e., for making current reversal in the short-circuited coil as sparkless as possible. They are, Resistance commutation. EMF commutation (it is done with the help of brush-lead or i…

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