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an investigation of dual stator winding induction machines

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If the rotor speed <strong>an</strong>d the rotor flux linkages are fixed to certain values <strong>an</strong>d the slip<br />

frequencies <strong>of</strong> both <strong>stator</strong> <strong>winding</strong>s are known, the corresponding dc voltages are<br />

expressed as:<br />

2<br />

Vdc1 V<br />

2<br />

− b ± b − 4ac<br />

= (9.20)<br />

2a<br />

⎛ R<br />

⎜<br />

⎝<br />

+ R<br />

⎞<br />

⎟<br />

⎠<br />

R<br />

R<br />

L1<br />

L3<br />

2<br />

L2<br />

L3<br />

dc2<br />

= ⎜ Vdc1<br />

− δ 1 + δ 2<br />

RL1R<br />

⎟<br />

(9.21)<br />

L3<br />

RL2<br />

+ RL3<br />

2<br />

⎡<br />

2<br />

2<br />

⎛ L<br />

⎤<br />

r1λdr1<br />

⎞ 2 ωr1λ<br />

dr1<br />

λdr1<br />

rr1<br />

2<br />

where, δ = − ⎢<br />

⎜<br />

⎟<br />

1 3 r1 ωs1<br />

+ ωs1<br />

+ r1<br />

− λ 1⎥<br />

2 2 dr ,<br />

⎢⎣<br />

⎝ rr1L<br />

m1<br />

⎠ rr1<br />

Lm1<br />

Lr1<br />

⎥⎦<br />

2<br />

⎡<br />

2<br />

2<br />

⎛ L<br />

⎤<br />

r 2λ<br />

dr 2 ⎞ 2 ωr<br />

2λ<br />

dr 2 λdr<br />

2 rr<br />

2 2<br />

δ = − ⎢<br />

⎜<br />

⎟<br />

2 3 r2 ω s2<br />

+ ω s2<br />

+ r2<br />

− λ 2 ⎥<br />

2 2 dr ,<br />

⎢<br />

⎣ ⎝ rr<br />

2L<br />

m2<br />

⎠ rr<br />

2 Lm2<br />

Lr<br />

2 ⎥<br />

⎦<br />

R<br />

+ R<br />

R<br />

⎛ R + R<br />

⎜<br />

⎝<br />

L1<br />

L3<br />

L2<br />

L1<br />

L3<br />

a =<br />

−<br />

2<br />

⎜ ⎟ ,<br />

RL1RL3<br />

RL2<br />

+ RL3<br />

RL1RL3<br />

c = −δ<br />

.<br />

2<br />

1<br />

⎞<br />

⎟<br />

⎠<br />

2<br />

319<br />

( δ 2 − δ 1 ) R L2<br />

R L1<br />

+ R<br />

+ 2 1<br />

( R + R ) R L1<br />

R L3<br />

b = δ<br />

R<br />

The contours <strong>of</strong> the dc voltages are shown in Figure 9.2 (a), where the contours <strong>of</strong> the<br />

ABC <strong>winding</strong> set rectifier output dc voltage are represented as sl<strong>an</strong>ting vertical dash lines<br />

while the contours <strong>of</strong> the dc output voltage <strong>of</strong> the rectifier connected to the XYZ <strong>winding</strong><br />

set are represented as horizontal solid lines. The dc voltage generated by the rectifier<br />

connected to the ABC <strong>winding</strong> set depends signific<strong>an</strong>tly on the slip frequency <strong>of</strong> the<br />

ABC <strong>winding</strong> set <strong>an</strong>d less on the slip frequency <strong>of</strong> the XYZ <strong>winding</strong> set. A similar<br />

conclusion applies to the second rectifier dc output voltage. To generate reasonable dc<br />

2<br />

output voltages from (9.20-9.21), the condition b − 4ac<br />

≥ 0 must be true, giving the<br />

L3<br />

L2<br />

L3<br />

L3<br />

<strong>an</strong>d

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