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an investigation of dual stator winding induction machines

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oundary <strong>of</strong> the rotor slip frequencies graphically illustrated in Figure 9.2 (b) for specific<br />

rotor speed <strong>an</strong>d rotor flux references.<br />

Reasonable dc voltages c<strong>an</strong> only be obtained when the choice <strong>of</strong> slip frequencies for<br />

the <strong>winding</strong> sets is within the possible regions shown in Figure 9.2(b). However, the first<br />

quadr<strong>an</strong>t is the feasible operability region. If the dc voltages <strong>an</strong>d rotor speeds are known,<br />

the relationship between the slip frequencies <strong>an</strong>d rotor flux linkages c<strong>an</strong> be found as<br />

shown in Figure 9.3(a) for the rectifier connected to the XYZ <strong>winding</strong> set, where the set<br />

dc output voltage is 200V <strong>an</strong>d five different rotor speeds r<strong>an</strong>ging from 1200 rpm to 3600<br />

rpm are considered.<br />

If the value <strong>of</strong> d-axis flux linkage is given <strong>an</strong>d the rectifier dc voltage <strong>of</strong> the ABC<br />

<strong>winding</strong> set is fixed, the boundary value <strong>of</strong> the rotor speed is expressed as:<br />

2<br />

2<br />

⎛ L ⎞ ⎡ ⎛ ⎞ ⎤<br />

r1<br />

r1<br />

rr1<br />

Vdc1<br />

Vdc1<br />

+ Vdc2<br />

2<br />

ω =<br />

⎜<br />

⎟ ⎢ − + ⎜<br />

⎟<br />

r1<br />

4r1 ⎜<br />

+ V<br />

2 2<br />

dc1<br />

⎟<br />

3λdr1⎥<br />

(9.22)<br />

⎝ Lm1<br />

⎠ ⎢⎣<br />

Lm1<br />

Lr1<br />

⎝ RL1<br />

RL3<br />

⎠ ⎥⎦<br />

A similar boundary equation c<strong>an</strong> be derived for the rectifier connected to the XYZ<br />

<strong>winding</strong> set. The boundaries for the possible generated dc voltages are shown in Figure<br />

9.3 (b), where the solid line represents the boundary for the rectifier connected to the<br />

ABC <strong>winding</strong> set while the dashed line gives the limits <strong>of</strong> the rectifier connected to the<br />

XYZ <strong>winding</strong> set. The right h<strong>an</strong>d side <strong>of</strong> the boundary lines gives the possible operating<br />

r<strong>an</strong>ge for the two rectifiers.<br />

320

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