The Theory Of Induction And Induction

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Introduction
Induction machines are classified into two which includes motors and generators. The basic principles of these motors can be applied and hence develop equations describing its behaviour. The most common motors include squirrel-cage, wound-rotor ranging from few horsepower to thousands as the case may be. Squirrel Cage Rotor consist of a bare copper, slightly longer than the rotor, while a wound rotor has a 3 phase windings, and are evenly distributed in the slots, usually connected in 3-wye. The resistors are mainly used during the start-up period under normal running conditions.

Diagram 1
The principle operation of these 3-Phase Induction Motor is related to the Faraday’s Law and Lorentz force on a conductor. Faradays
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1.1 Background

Induction Motor tolerate a level of unbalance. The variable speed drive are also affected as a result of the voltage unbalance which consist of three phase rectifier system. Unbalanced voltage is caused by mismatch of reactive power between generating and industrial stations, hence it can be classified BOV (Balanced Overvoltage), phase voltages greater than rated voltage. BUV (Balanced Under voltage), phase voltages lesser than rated voltage. UBOV (Unbalanced Overvoltage), phase voltage not equal to each other, therefore the positive sequence component is greater than rated voltage and finally UBUV (Unbalanced Under voltage), voltages are not equal, and hence the positive sequence component is lesser
NEMA (National Equipment Manufacturers Association) definition “Voltage unbalanced, given by”;
█( @Maximum voltage derivation from the average line voltage)/(Average Line Voltage) X 100------[1]

IEEE definition “phase voltage unbalance rate is given by”;
█( @Maximum voltage derivation from the average line voltage)/(Average Line Voltage) X 100------[2]

Figure 1.1: Simple Equivalent circuit for an induction motor.
The circuit above illustrates a simple squirrel cage motor, which is widely used, with a simple and rugged construction, with a minimum maintenance, high reliability and efficiency, and can operate without no further
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