Paul M. Espelage

Symmetrical GTO current source inverter for wide speed range control of 2300 to 4160 volt, 350 to 7000 hp, induction motors

A line of variable-speed 2300-4160 V, 350-7000 hp induction-motor drives for either fan or constant torque load applications is described. The drives are current-sourced, consisting of one or two six-pulse thyristor phase-controlled source converters in series, a DC link reactor, a six-pulse, symmetric-GTO (gate-turn-off), load inverter, a three-phase load capacitor in parallel with the induction motor. The drive features a wide speed range of operation, high inverter efficiency, and good motor current and voltage waveshape over the speed range.<<ETX>>

A High-Performance Controlled-Current Inverter Drive

A production variable-frequency drive is described which uses an induction motor and a controlled-current inverter. The control loops of the drive have been arranged so that the performance of the drive is extended to zero speed and to the theoretical upper limit speed. Operating modes include torque smoothing by programmed dc link current, pulsewidth modulated (PWM) current shaping, and flux-controlled constant horsepower operation.

A Wide-Range Static Inverter Suitable for AC Induction Motor Drives

A dc to ac, variable voltage, variable frequency, three-phase, external impulse commutated inverter, rated at 200 kVA, is described that controls the speed of an induction motor that is suitable for traction applications. The inverter is supplied from a variable voltage dc source for the load circuit and a fixed voltage dc source for the commutation circuit. Isolation between the two sources is provided by a high-frequency pulse transformer. The output ac voltage is controlled from 0 to 250 volts; the output frequency is controlled from 4 to 400 Hz. The load is a low-slip, 12 000 r/min induction motor with a continuous rating of 15 hp over a 10:1 speed range, and 60 hp over a 2:1 speed range. The theory of operation and design equations for the inverter power circuit, the design and construction of the motor, and the test results of the inverter-motor combination are presented.