| 摘要 |
PROBLEM TO BE SOLVED: To prevent the breakage of the semiconductor switching element of the main circuit and stably control the element, by providing a limiting value for limiting a voltage command so that the command cannot exceed the amplitude of carriers, and controlling the voltage command based on the limiting value. SOLUTION: A voltage command V* is generated by multiplying a signal outputted from a waveform generating circuit 51 based on the phase of a voltage command by a modulation factor λ* and a bias B is added to or subtracted form the command V* by means of adders 66 and 65. A PWM signal is generated based on voltage commands VA* and VB* thus obtained. When the modulation factor λ* does not exceed a limiting value (Lmax -B), the outputs of correction amount computing circuits 36 and 37 become '0'. In an area where the magnitude of the modulation factor λ* exceeds the limiting value (Lmax -B), on the other hand, the voltage command values VA* and VB* are limited to the limiting value Lmax , because the value obtained by adding or subtracting the bias B to the voltage command V* exceeds the limiting value Lmax . Then, the output meeting the voltage command is outputted by correcting the shortage with the other voltage command. |
