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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 number <strong>of</strong> poles for the <strong>winding</strong> set increases. Hence, the 2-pole <strong>induction</strong> machine<br />

has the worst perform<strong>an</strong>ce <strong>an</strong>d much greater harmonic current components under rotor<br />

eccentricity conditions. Under the steady state operating condition, the Fourier series<br />

components <strong>of</strong> one phase current <strong>an</strong>d the electromagnetic torque <strong>of</strong> both the ABC <strong>an</strong>d the<br />

XYZ <strong>winding</strong> sets are shown in Fig. 4.32. It is observed that the two-pole <strong>winding</strong> set has<br />

lower frequency (torque, current) harmonic components when compared to the 6-pole<br />

<strong>winding</strong> set.<br />

From [4.1], the principal slot harmonics (PSH) <strong>of</strong> the <strong>induction</strong> machine c<strong>an</strong> be<br />

expressed as:<br />

⎛ 1−<br />

s ⎞<br />

PSH = ⎜ R ± 1⎟<br />

f<br />

⎝ p ⎠<br />

185<br />

(4.17)<br />

where, R is the rotor bar number; s is the slip; p is the pole pair number <strong>of</strong> the<br />

machine <strong>an</strong>d f is the input voltage frequency. From the machine parameters shown in<br />

the Appendix for the ABC <strong>winding</strong> set, the calculated PSH is 853.2 Hz for s = 0.<br />

02 . The<br />

spectrum <strong>of</strong> the simulated phase A current shown in Figure 4.32(a) shows that the PSH is<br />

signific<strong>an</strong>t. Some harmonic frequency components, because <strong>of</strong> the mixed rotor<br />

eccentricity c<strong>an</strong> also be found around the PSH, which coincide with the results obtained<br />

in the previous work [4.1, 4.6]. For the XYZ <strong>winding</strong> set, the simulated current spectrum<br />

did show the principal slot harmonic. However, only the PSH is signific<strong>an</strong>t <strong>an</strong>d the other<br />

harmonic frequencies around it are almost invisible. For this machine, under the rotor<br />

eccentricity condition it is easier for the PSH in the currents <strong>of</strong> the 2-pole ABC <strong>winding</strong><br />

set to be detected.

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