| 摘要 |
PURPOSE:To enhance the torque of a motor within a range of the prescribed voltage by holding the amplitude of a modulation signal at the constant times of a basic positive arcuate wave, and forming a waveform containing a plurality of harmonics of odd power. CONSTITUTION:With a phase signal theta as an address a modulation signal of the maximum amplitude (1/2)X3<1/2> is read out from a memory 1, and those for three phases are generated. Multipliers 2-4 multiply the modulation signal by a voltage command A for controlling the gain of the signal to obtain a modulation signal limited to the amplitude (a/2)X3<1/2>. On the other hand, a carrier generator 5 generates a carrier signal of a triangular wave synchronized with the modulation signal in the frequency of (3+6n) times of the signal of the modulation signal. Comparators 6-8 compare the carrier signal with the modulation signal to generate 3-phase PWM signal, thereby operating an inverter 9. The drive current contains low frequency harmonics, a large torque is generated in a motor 10, and a torque ripple and the copper loss of the harmonics remain low. |
