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an investigation of dual stator winding induction machines

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Figure 7.30. The percentage <strong>of</strong> the torque from the XYZ <strong>winding</strong> set when the total<br />

electromagnetic torque <strong>an</strong>d the rotor mech<strong>an</strong>ical speed are const<strong>an</strong>t while the slip frequency <strong>of</strong><br />

the ABC <strong>winding</strong> set ω s1<br />

is varied from –10 rad/s to 10 rad/s.<br />

In the low speed r<strong>an</strong>ge, the relationship between two slip frequencies under different<br />

const<strong>an</strong>t rotor mech<strong>an</strong>ical speeds is shown in Figure 7.27. Similar to what it is found in<br />

Figure 7.21, the slip frequency <strong>of</strong> the XYZ <strong>winding</strong> set is always positive while the ABC<br />

<strong>winding</strong> set moves from generating condition to motor condition. In the low speed r<strong>an</strong>ge,<br />

a minimum copper loss operating point c<strong>an</strong> be found under a const<strong>an</strong>t output mech<strong>an</strong>ical<br />

power condition to greatly reduce the loss <strong>of</strong> the machine. The electromagnetic torque<br />

contributions <strong>of</strong> the ABC <strong>an</strong>d XYZ <strong>winding</strong> set in the low speed r<strong>an</strong>ge are shown in<br />

Figure 7.29 <strong>an</strong>d Figure 7.30 respectively.<br />

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