| 摘要 |
PROBLEM TO BE SOLVED: To reduce the harmonic components in torque and ripple torque changing rates even at the time of rectangular wave conduction by turning on switching elements which are conducted to a plurality of phases of motor driving coils in a prescribed direction and prescribed order beyond a specific electrical angle from the zero-crossing point of an induced voltage. SOLUTION: The signal of a position detecting circuit 2 changes to 'H' from 'L' after, for example, a U-phase induced voltage changes to an electrical angle of 35 deg. from the zerocrossing point when the voltage changes to positive from negative. A drive circuit 5 detects the signal and a switching element turning-on means 5a turns on a switching element 3au . After the electrical angle reaches 60 deg., the signal changes to 'L' from 'H' and, at the same time, a switching element 3bv is turned off and another switching element 3 is turned on. When the electrical angle reaches 120 deg. thereafter, the signal changes to 'H' from 'L' and, at the same time, the switching element 3au is turned off and a switching element 3av is turned on. Since the U-phase induced voltage component is low, the circulating period of the current flowing through a diode 7au becomes longer and the dropping of the sum of the u-phase circulating current flowing through a drive coil 4 and a V-phase transient build-up current becomes smaller. |
