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Modulation of the Chopping Frequency in DC Choppers and PWM Inverters Having Current-Hysteresis Controllers

1984; Institute of Electrical and Electronics Engineers; Volume: IA-20; Issue: 4 Linguagem: Inglês

10.1109/tia.1984.4504485

1939-9367

William McMurray,

Silicon Carbide Semiconductor Technologies

In a dc chopper converter having its load current regulated by a feedback controller of the fixed hysteresis type, the chopping frequency is shown to depend on the square of the counter EMF of the load. In a pulsewidth modulated (PWM) inverter, the counter EMF is modulated at the output frequency, so the chopping frequency is modulated at twice the output frequency. For a three-phase PWM inverter feeding a three-wire load, the chopping frequency modulation is not smooth. This is explained to be a consequence of the fact that the three phase currents must sum to zero, rendering one of the three current controllers redundant.