A slip power recovery scheme with a PWM (pulsewidth-modulation) converter in the rotor circuit is investigated. The steady-state performance characteristics, such as speed-torque characteristics and the overall power factor of the drive system, are determined using simple DC and AC equivalent circuits. The performance characteristics are verified experimentally, showing good agreement with theoretical results. The power factor of the drive system is improved significantly over the entire range of speed control. The drive provides speed-torque characteristics similar to those of a separately excited DC motor. Oscillograms of typical waveforms from the experimental set-up are illustrated to demonstrate the satisfactory performance of the scheme.
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