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an investigation of dual stator winding induction machines

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<strong>winding</strong> set works as a generator, while the other three-phase <strong>winding</strong> set is<br />

working as a motor. This operating condition may be useful at low speeds.<br />

Then the expression <strong>of</strong> the average torque is the next step. If the inverse slip<br />

condition is applied, the first term <strong>of</strong> torque from ABC <strong>winding</strong> is expressed as:<br />

T<br />

Nr<br />

⎧ µ r 2<br />

*<br />

( ( ) ) ⎫<br />

0 ⎛<br />

P1<br />

⎞<br />

− j P1<br />

i−1<br />

αr<br />

−π<br />

rl Re⎨<br />

j 2 ⎜3C<br />

s1<br />

⋅ I s1<br />

⋅ CR<br />

⎟ ⋅ IiR2<br />

⋅ e ⎬ (5.112)<br />

⎩ − gP1<br />

⎝<br />

⎠ i 1<br />

⎭<br />

eABC1<br />

= ∑<br />

=<br />

Under steady state condition, the rotor current distribution follows the sinusoidal<br />

function, which is written as:<br />

I<br />

iR2<br />

= I<br />

R2<br />

⋅ e<br />

( P ⋅(<br />

i−1)<br />

⋅α<br />

+ ε )<br />

j<br />

2 r<br />

(5.113)<br />

where, the complex number I R2<br />

represents the magnitude <strong>of</strong> the rotor current<br />

induced by the XYZ <strong>winding</strong> set; ε is a general shift <strong>an</strong>gle between the rotor<br />

currents induced by the XYZ <strong>winding</strong> <strong>an</strong>d physical rotor loops fixed by the ABC<br />

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

Substituting (5.113) into (5.112), the first term <strong>of</strong> T eABC becomes,<br />

T<br />

Nr<br />

⎧ µ r 2<br />

*<br />

[ ( )( ) ] ⎫<br />

0 ⎛<br />

P1<br />

⎞<br />

j P2<br />

−P1<br />

⋅ i−1<br />

⋅α<br />

r + ε<br />

−π<br />

rl Re⎨<br />

j 2 ⎜3C<br />

s1<br />

⋅ I s1<br />

⋅C<br />

R ⎟⋅<br />

I R2<br />

⋅e<br />

⎬ (5.114)<br />

⎩ − gP1<br />

⎝<br />

⎠ i 1<br />

⎭<br />

eABC1<br />

= ∑<br />

=<br />

Since the pole numbers <strong>of</strong> two <strong>stator</strong> <strong>winding</strong>s are unequal, the sum <strong>of</strong> terms yield<br />

zero, i.e:<br />

Nr<br />

j<br />

∑ e<br />

i=<br />

1<br />

[ ( P −P<br />

)( ⋅ i−1)<br />

⋅α<br />

+ ε ]<br />

2 1 r =<br />

0<br />

223<br />

(5.115)<br />

Similar result is obtained for the first term <strong>of</strong> T eXYZ . It c<strong>an</strong> be concluded that the<br />

potential additional torque due to this term is zero under steady state operating<br />

condition. However, since the rotor current distribution assumption is only good

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