| 摘要 |
In a PWM inverter using a three-arm modulation method, the apparatus and method are for controlling the current without missing the zero vector by switching the method to a two-arm modulation method near the voltage saturation. A PWM inverter using a three-arm modulation method comprises a timing data generating unit (32) which generates the timing data for the three-arm modulation based on the voltage vector times T lambda , T mu , and T0 from a PWM pattern operating unit (31), a timing change-over switch (33) which switches over this timing data to each phase time, and a timing data generating unit (41) which generates the timing data for the two-arm modulation from the voltage vector times. The zero vector time T0 is compared with the set value K.Tdly for the dead time compensation by a comparison circuit (45) having the so-called hysteresis. Thus, if the zero vector time becomes short, the data generated by the timing data generating unit (41) are output to the timing change-over switch (33) by a modulation change-over switch (47) so that the PWM pattern is for the two-arm modulation method.
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