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an investigation of dual stator winding induction machines

an investigation of dual stator winding induction machines

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Figure 7.18 Power factor speed characteristics when f = 30 Hz <strong>an</strong>d f = 85 Hz<br />

From the above simulation results, it is found that when the ratio <strong>of</strong> the input<br />

frequencies <strong>of</strong> the ABC <strong>an</strong>d XYZ <strong>winding</strong> sets is 3, both <strong>winding</strong> sets are working in the<br />

motoring mode. However, when the frequency ratio is not 3, i.e. frequency synchronous<br />

operation, the synchronous speed <strong>of</strong> the <strong>dual</strong> <strong>stator</strong> <strong>winding</strong> <strong>induction</strong> machine depends<br />

on the two frequencies. The <strong>winding</strong> set that has input frequency less th<strong>an</strong> the rated value<br />

works as a generator before reaching the synchronous speed. The power factor decreases<br />

when the rotor speed decreases.<br />

In the second part <strong>of</strong> the steady state <strong>an</strong>alysis, the relationships between slip<br />

frequency, rotor speed <strong>an</strong>d electromagnetic torque are studied. There are four variables in<br />

the final torque equation--electromagnetic torque T e , rotor mech<strong>an</strong>ical speed ω rm ,<br />

electric speed <strong>of</strong> ABC <strong>winding</strong>s ω e1<br />

<strong>an</strong>d electric speed <strong>of</strong> XYZ <strong>winding</strong>s e2<br />

272<br />

abc<br />

xyz<br />

ω . If <strong>an</strong>y<br />

three <strong>of</strong> them are known, the last one c<strong>an</strong> also be calculated. Different <strong>an</strong>alysis results<br />

will be achieved if different conditions are applied. However, it should be noticed that

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