A background discussion of induction machine equivalent circuits, including operation as an induction generator, is provided. Selective shorting of the machine terminals is described, to convert at least some of the mechanical input energy into electrical field energy for the machine. Systems are described for accomplishing the selective shorting with a single-phase machine, including sensing of the zero-crossing of the output voltage to insure that the shorting is effected at the appropriate time to replenish the field. The shorting time duration can be varied as a function of load. A three-phase shorting circuit is also described.
A rotary induction generator having a stator with stator windings defining a three-phase stator and a rotor mounted for rotation therein, and having wound thereon three rotor windings defining a three-phase rotor and having resistive-reactive means connected to said secondary windings to increase the efficiency of said generator and limit the power output to the capacity of the generator over a wide range of speeds.
A method and circuit are presented for operating a polyphase dc motor in which substantially sinusoidal drive voltages are applied to the windings of the motor in predetermined phases. Zero crossings of currents flowing in respective windings of the motor are detected, and phases of the drive voltages are adjusted to have zero crossings substantially simultaneously with the detected zero crossings of the currents flowing in respective windings of the motor. The method and circuit results in motor operation with significantly reduced acoustic motor noise.
A slowly rotating synchronous generator (ring generator) for a wind power installation, the generator having a rotor and a stator surrounding the rotor, and the stator having at least one three-phase current winding on which a capacitive current is impressed, and the generator having a part of the exciter power of the generator produced by the stator.
In an induction generator, an additional set of stator windings is provided, separate from and secondary to the main stator windings upon which the generator's output voltage is generated and supplied to the load. This separate stator winding is provided for the purpose of supplying the generator with the reactive electrical power it needs to maintain the rotating stator field and supplying any reactive power needed by the load. Thus, there is no need to use a capacitor assembly, for supplying the reactive power needed by the generator. Currents are injected into this separate winding in such a way that only reactive power is supplied to the generator. Specifically, a power measuring circuit measures the power in the additional set of stator windings, and a power error signal is formed by algebraically adding the outputs of the power measuring circuit. The power error signal is further processed and supplied as a timing control signal for generating the injected currents, which are maintained 90 degrees out of phase with an excitation voltage curve.
A rotary induction machine in which operating characteristics of the machine are controlled by adding impedance elements to the rotor windings in which the impedance elements are stationary and connected to the rotor windings by a rotary transformer.
