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an investigation of dual stator winding induction machines

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6.4 Simulation <strong>an</strong>d Experimental Results<br />

The impact <strong>of</strong> the main flux saturation on the tr<strong>an</strong>sient <strong>an</strong>d dynamic perform<strong>an</strong>ce <strong>of</strong><br />

the machine was investigated through the computer simulation <strong>of</strong> the machine using the<br />

air-gap flux linkage alignment methodology set forth in Section 6.3. The const<strong>an</strong>t<br />

machine parameters are given in Table 6.1 <strong>an</strong>d the values <strong>of</strong> the mutual induct<strong>an</strong>ces<br />

depend on the flux level. These c<strong>an</strong> be calculated using the curves given in Figure 6.6.<br />

Figure 6.7 presents the simulation results <strong>of</strong> the free acceleration starting process <strong>of</strong> the<br />

saturated machine. The line-to-line voltages <strong>an</strong>d its frequencies supplied to ABC <strong>winding</strong><br />

set are 65V <strong>an</strong>d 30 Hz, respectively, while the corresponding line-line voltages <strong>an</strong>d<br />

frequency supplied to the XYZ <strong>winding</strong> set are 195V <strong>an</strong>d 90 Hz respectively. Some<br />

comparative experimental results obtained under the same input voltage conditions are<br />

given in Figure 6.9 <strong>an</strong>d are very similar to the simulation results. The dynamic responses<br />

<strong>of</strong> the machine to ch<strong>an</strong>ges in load are shown in Figure 6.8. When the rotor speed is<br />

const<strong>an</strong>t <strong>an</strong>d in steady-state, the load torque is ch<strong>an</strong>ged from 0 Nm to 5.5 Nm to show the<br />

effect <strong>of</strong> the main air-gap flux linkage saturation on the machine perform<strong>an</strong>ce. The flux<br />

linkage on the q-axis is very small while the air gap flux linkage is aligned with the d-<br />

axis. The variations <strong>of</strong> the magnetizing induct<strong>an</strong>ces <strong>of</strong> two <strong>stator</strong> <strong>winding</strong> sets are shown<br />

in Figure 6.7 (g-h) <strong>an</strong>d Figure 6.8 (g-h). Figure 6.10 illustrates experimentally the<br />

dynamics due to a load ch<strong>an</strong>ge, which also compares favorably with the computer<br />

simulations result when the saturation effect is accounted for.<br />

249

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