| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce torque ripple of a brushless motor. <P>SOLUTION: When a switching element is switched from ON to OFF in overlap conduction for conducting the armature coils of respective phases while overlapping before and after commutation, duty ratio for the switching element is lowered gradually at a constant rate over a specified time t. Consequently, the torque constant during commutation increases gradually at a constant rate from torque constant T<SB>K3</SB>at the time of three-phase conduction to torque constant T<SB>K2</SB>at the time of two-phase conduction. When switching is made from three-phase conduction to two-phase conduction, a control current is decreased to about 90% of the level at the time of three-phase conduction at a constant rate matching the variation rate of torque constant by lowering the duty ratio of a load side switching element. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
