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Abstract

An apparatus for carrying out a current control and method therefor are disclosed in which the current control is such that no 0 vector defect is present by switching from a three-arm modulation method to a two-arm modulation method in the vicinity to a voltage saturation in a PWM inverter using the three-arm modulation method. The structure of the current control apparatus is such that in the PWM inverter using the three-arm modulation method having a time point data preparing section which prepares a time point data for the three-arm modulation mode from voltage vector times T .lambda., T.mu., and To derived by a PWM pattern calculation section (31) and a time point chaneover switch (33) which changes the time point data to each phase time point, a time point data preraring section (41) which prepares the time point data for the two-arm modulation mode from the voltage vector times is provided, a comparator (45) having a so-called hysterisis (window-formed) characteristic which compares the 0 vector time To and dead time compensation set value K.Tdly is provided so that when the 0 vector time becomes smaller, the modulation changeover switch (47) outputs a signal to the time point changeover switch (33) so that the data of the time point data preparing section (41) gives the PWM pattern of the two-arm modulation method.

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