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an investigation of dual stator winding induction machines

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1.2.4 Field Analysis Method<br />

In [5.1], rotating-field theory has been used to develop a general model <strong>of</strong> a squirrel-<br />

cage <strong>induction</strong> machine having a general <strong>winding</strong> connection <strong>an</strong>d <strong>an</strong>y supply<br />

configuration. Hence, this methodology is called the field <strong>an</strong>alysis method in this<br />

dissertation. The coupling imped<strong>an</strong>ce model that relates the EMF induced in <strong>an</strong>y circuit<br />

<strong>of</strong> the machine to the current flowing in all the other circuits is the basis <strong>of</strong> this <strong>an</strong>alysis<br />

method. Although the original idea <strong>of</strong> the author in [5.1] is to study the power factor issue<br />

<strong>of</strong> a cage rotor <strong>induction</strong> machine, this method c<strong>an</strong> be applied to study the rotating field<br />

<strong>of</strong> electric <strong>machines</strong> in other areas. The application <strong>of</strong> this method to the underst<strong>an</strong>ding <strong>of</strong><br />

the asynchronous <strong>an</strong>d synchronous operation <strong>of</strong> the “brushless doubly-fed machine” has<br />

been demonstrated in [1.8]. A mathematical model based on the field <strong>an</strong>alysis method for<br />

the <strong>an</strong>alysis <strong>of</strong> a brushless doubly-fed machine is the contribution <strong>of</strong> that work.<br />

1.2.5 Saturation Effects<br />

In a <strong>dual</strong> <strong>stator</strong> <strong>winding</strong> <strong>induction</strong> machine, since the air-gap flux linkages created by<br />

the two <strong>stator</strong> <strong>winding</strong> sets <strong>an</strong>d the induced rotor currents share the same magnetic loop,<br />

the main air-gap flux saturation phenomenon is more complicated th<strong>an</strong> that <strong>of</strong> the normal<br />

single <strong>stator</strong> <strong>winding</strong> squirrel-cage <strong>induction</strong> machine [6.3, 6.5]. Because <strong>of</strong> this<br />

complexity, a reconsideration <strong>of</strong> main flux linkage saturation effect is called for in the<br />

design <strong>of</strong> the machine <strong>an</strong>d in the development <strong>an</strong>d practical implementation <strong>of</strong><br />

speed/torque control algorithms. To avoid deep magnetic saturation in the <strong>stator</strong> <strong>an</strong>d rotor<br />

cores, rotor <strong>an</strong>d <strong>stator</strong> teeth, magnetic design methodologies have been suggested both for<br />

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