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an investigation of dual stator winding induction machines

an investigation of dual stator winding induction machines

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The no-load starting tr<strong>an</strong>sient simulation results are shown in Figure 3.10 when the<br />

machine is fed with voltages satisfying the const<strong>an</strong>t voltage/Hertz open-loop control<br />

algorithm in which the ratios <strong>of</strong> the frequency <strong>of</strong> the 6-pole <strong>stator</strong> <strong>winding</strong> set to those <strong>of</strong><br />

the 2-pole <strong>stator</strong> <strong>winding</strong> set is 3. The frequencies <strong>of</strong> the ABC (2-pole) <strong>an</strong>d XYZ (6-pole)<br />

<strong>stator</strong> <strong>winding</strong> sets are 30 Hz <strong>an</strong>d 90 Hz respectively. The line-to-line voltages <strong>of</strong> the<br />

ABC (2-pole) <strong>an</strong>d XYZ (6-pole) <strong>stator</strong> <strong>winding</strong> set are 67 V <strong>an</strong>d 202 V respectively. The<br />

rotor speed starts from zero <strong>an</strong>d ramps up to steady state smoothly. The tr<strong>an</strong>sient current<br />

is big, but all the currents are reduced to almost zero at the no load steady state condition.<br />

During the steady-state operation, a 3Nm load torque is added to the machine to check<br />

the dynamic response <strong>of</strong> the system. The simulation results <strong>of</strong> the dynamic response are<br />

shown in Figure 3.11. It is observed that the ABC <strong>stator</strong> <strong>winding</strong> set contributes a smaller<br />

percentage <strong>of</strong> the generated electromagnetic torque to meet the load dem<strong>an</strong>d. This torque<br />

distribution is determined by the machine design.<br />

Three <strong>of</strong> the rotor bar currents are chosen for illustration. The rotor bar currents<br />

during the starting process are shown in the Figure 3.12 <strong>an</strong>d the rotor bar currents during<br />

the steady state at loaded condition are shown in the Figure 3.13.<br />

In the second case, the frequency <strong>of</strong> the input voltages <strong>of</strong> the ABC <strong>winding</strong> set is set<br />

to 27 Hz while that <strong>of</strong> the XYZ <strong>winding</strong> set is set at 90 Hz, both operating with the same<br />

Voltz/Hz ratio. It is observed that the 2-pole (ABC) <strong>winding</strong> set is generating with<br />

negative electromagnetic torque, the XYZ (6-pole) <strong>winding</strong> set needs to provide load<br />

torque <strong>an</strong>d counteract the negative torque produced by the ABC <strong>winding</strong> set. The<br />

simulation results for both the starting process <strong>an</strong>d dynamic response are shown in Figure<br />

3.14 <strong>an</strong>d Figure 3.15 respectively. Three <strong>of</strong> the rotor bar currents are shown in Figure<br />

122

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