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an investigation of dual stator winding induction machines

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CHAPTER 5<br />

FIELD ANALYSIS OF DUAL STATOR WINDING<br />

INDUCTION MACHINE<br />

5.1 Introduction<br />

The <strong>dual</strong> <strong>stator</strong> <strong>winding</strong> <strong>induction</strong> machine is a special design based on the<br />

convention squirrel-cage <strong>induction</strong> machine. Two <strong>stator</strong> <strong>winding</strong> set with different<br />

numbers <strong>of</strong> poles share a common squirrel cage rotor. These two <strong>stator</strong> <strong>winding</strong> sets have<br />

been proven to be completely decoupled as shown in [1.11], however a potential coupling<br />

between the <strong>stator</strong> <strong>winding</strong> sets through the common rotor bar currents may exist. Are<br />

these two <strong>stator</strong> <strong>winding</strong> sets coupled or not? How do the fields interact with each other?<br />

Is there <strong>an</strong>y electromagnetic torque component due to the coupling <strong>of</strong> two <strong>stator</strong> <strong>winding</strong><br />

sets? All these questions are very relev<strong>an</strong>t in this special machine <strong>an</strong>d will be <strong>an</strong>swered in<br />

this chapter.<br />

The <strong>an</strong>alysis method proposed by Williamson for <strong>an</strong> <strong>induction</strong> machine having a<br />

general <strong>winding</strong> connection <strong>an</strong>d <strong>an</strong>y supply configuration in [5.1] has been found to be<br />

suited to the field <strong>an</strong>alysis <strong>of</strong> electric <strong>machines</strong>. The well-known rotating-field theory<br />

together with a coupling imped<strong>an</strong>ce model is used. The application <strong>of</strong> this method to the<br />

underst<strong>an</strong>ding <strong>of</strong> the asynchronous <strong>an</strong>d synchronous operation <strong>of</strong> the “brushless doubly-<br />

fed machine” has been demonstrated in [1.8]. Recently, the brushless doubly-fed<br />

<strong>induction</strong> machine has been understood deeply through the development <strong>of</strong> the steady-<br />

state equivalent circuit, discussion <strong>of</strong> design issues <strong>an</strong>d operation as either as a generator<br />

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