Variable speed a-c drive

Details Variable speed a-c drive Variable speed a-c drive

1988-01-27

1989-03-21

Wong, Peter S.

Electric power conversion systems

Current conversion

Including an a.c.-d.c.-a.c. converter

363 65, 318803, H02M 545

Patent

active

048149640

ABSTRACT:
A load commutated inverter (LCI) a-c drive system includes a synchronous motor with two 30 degree angularly displaced sets of three-phase windings. Each set of motor windings is powered by a three-phase inverter fed by a three-phase rectifier in a separate d-c loop. The three-phase rectifiers are fed by either a generator with two angularly displaced sets of three-phase windings or by a transformer with a three-phase primary winding, and delta and wye secondary windings separately supplying the two rectifiers. Twelve-pulse operation in the line commutated mode with substantially constant d-c link currents significantly reduces torque pulsations. At low speeds, sinusoidal segment pulsed d-c currents in the d-c links are gated to pairs of windings in the two sets of motor windings which generate component MMFs either 90 degrees or 150 degrees displaced to produce a resultant rotating motor MMF of constant magnitude to completely eliminate torque pulsations. Since the repetition rates of the pulsed d-c link currents in these two instances are 2 and 1.2 times the fundamental motor frequency respectively, the range of motor speeds over which torque pulsations can be completely eliminated is substantially increased, while torque pulsations at all higher speeds are greatly reduced.

REFERENCES:
patent: 4084220 (1978-04-01), Aramatsu
patent: 4392099 (1983-07-01), Kuniyoshi
patent: 4426611 (1984-01-01), Espelage et al.
A New Traction System Via Self-Controlled Synchronous Motors for Electric Locomotives, by A. Cossie et al., PCI '81 Proceedings, 417-434 and 436.

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