Importance

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Abstract

In a polyphase machine, being either a motor or a generator, there is provided a stator core having main stator windings and control windings. In the example of a squirrel cage induction motor these windings are wound about the stator core and the main windings have a capacitor connected in series with each such winding. In a three phase motor the control windings wound on the stator have currents in each phase which are substantially in phase at no load with the currents of the corresponding radially adjacent the main windings. Such currents become out of phase with their main winding currents as the load increases. The control windings are wound in an opposite sense to the corresponding main windings such that at low load the net flux density is low and as the load increases the flux density increases. Increase of starting and breakdown torque is achieved by having the respective poles created by the main windings and those created by the control windings placed to create a force because of the symmetry of the magnetic field. In this case the centers of the poles of the control windings are placed as close as physically possible between the poles of the main windings, thereby improving the magnetic centering of the poles. The voltage across the capacitor added to the input voltage may cause the stator core to switch periodically between non-saturated and saturated conditions.

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First Claim