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an investigation of dual stator winding induction machines

an investigation of dual stator winding induction machines

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Using the rotating-field theory <strong>an</strong>d coupling magnetic circuit theory, a fundamental<br />

underst<strong>an</strong>ding <strong>of</strong> the generated voltages <strong>an</strong>d possible developed electromagnetic torque<br />

components <strong>of</strong> the <strong>dual</strong> <strong>stator</strong> <strong>winding</strong> squirrel-cage <strong>induction</strong> machine has been set forth<br />

for the first time. The adv<strong>an</strong>tage <strong>of</strong> this method is the opportunity to clearly show all the<br />

frequency components <strong>an</strong>d the corresponding magnitudes <strong>of</strong> induced voltages,<br />

unsaturated air-gap flux linkages <strong>an</strong>d components <strong>of</strong> the developed electromagnetic<br />

torque. The development <strong>of</strong> the torque equations show that under certain operating<br />

conditions, some additional torque components may be created only during the tr<strong>an</strong>sient<br />

process, however the average torque will disappear under steady state condition. Relev<strong>an</strong>t<br />

computer simulation resulting from two different machine models are provided to show<br />

the possible equal slip frequency operating condition <strong>of</strong> the motor to yield <strong>an</strong> additional<br />

torque component during the tr<strong>an</strong>sient process. This operational mode is not predicted<br />

when the <strong>dual</strong> <strong>stator</strong> <strong>winding</strong> <strong>induction</strong> machine is modeled <strong>an</strong>d <strong>an</strong>alyzed as two<br />

independent <strong>induction</strong> <strong>machines</strong> coupled by the rotor shaft since the generated torque<br />

components are due to the <strong>stator</strong> <strong>winding</strong> currents <strong>of</strong> the indivi<strong>dual</strong> <strong>winding</strong> sets<br />

interacting with the total rotor currents.<br />

A study <strong>of</strong> the influence <strong>of</strong> magnetic circuit saturation on the main air-gap flux density<br />

comprising <strong>of</strong> flux density components having different pole numbers has been set forth<br />

in which the consequences <strong>of</strong> the phase <strong>an</strong>gle between the flux density components are<br />

explored. For the 2/6 pole <strong>dual</strong>-<strong>stator</strong> <strong>winding</strong> machine, the two pole <strong>winding</strong> set induces<br />

a voltage on the 6-pole <strong>winding</strong> set when the air-gap flux density saturates due to<br />

saturating rotor <strong>an</strong>d <strong>stator</strong> teeth. The various air-gap space harmonics generated due to<br />

magnetic saturation for the 2/6 <strong>winding</strong> sets have been discussed. There is <strong>an</strong> inter-<br />

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