Borgwarner Inc.

David James Gritter

George H Studtmann

A plural switch matrix is connected as a direct ac-to-dc converter between an induction generator and an a-c load. The generator provides three-phase output energy which is switched and controlled by the converter, to supply a controlled three-phase quasi-square wave (QSW) voltage to a load. The converter switching provides periodic shorts across the generator terminals, translating some of the mechanical input energy into electrical energy to sustain the generator field. The converter is regulated by gating signals from a combinational logic circuit.

Three-phase, quasi-square wave VSCF induction generator system

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 then described.

Excitation system for multi-phase induction generator

The disclosed voltage generating system includes certain known components, such as an induction machine driven as a generator, the output connections of which are coupled to the normal load connections of a switching system, which can be a bridge-type inverter. The system switching frequency f.sub.1 is regulated by firing pulses from a logic circuit in turn controlled by an oscillator. By controlling operation of the inverter switches with respect to the synchronous frequency (mechanical rotational speed) of the machine, a d-c voltage is provided on the normal inverter bus conductors. In the disclosed system the conventional inverter switches (such as SCR's) are replaced by true two-way power switches, capable of passing current in either direction. In addition the firing signals provided by the usual logic circuit and applied to these power switches are modified so that the switching occurs as a function not only of the first oscillator frequency f.sub.1 but also of signals received from a second oscillator at a frequency f.sub.2. In brief, the switching is accomplished with a gate circuit including an exclusive OR arrangement, fed by both the first and second oscillators, to produce an a-c output voltage on the inverter bus conductors. The frequency of this a-c output voltage is controllable independently of the generator speed, and the output voltage amplitude is controllable independently both of generator speed and load variations. By using an induction machine with multiple windings, and plural switching systems, multi-phase voltages can be supplied over multiple conductors to energize an a-c load.

Variable speed, constant frequency induction generator system

A bipolar inverter circuit comprises power switches for providing alternating energy to the load notwithstanding the polarity of the energizing voltage. Each leg of the bipolar inverter or power conversion circuit includes a pair of power switches, each having a diode bridge with a thyristor coupled across the normal bridge output terminals to complete a path for current flow through the power switch when the thyristor is gated on. Each leg also has a complementary commutating circuit for turning off one of the thyristors whenever the other is gated on.

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Elmhurst, IL, United States of America

David James Gritter