| 摘要 |
PROBLEM TO BE SOLVED: To suppress the increase in the amount of wind near an area where static pressure is equal to zero and to suppress the decrease in the maximum static pressure, by quickening conduction timing for the phase of an induced voltage for a high rotary region and delaying conduction timing for the phase of the induced voltage for a low rotary region. SOLUTION: When pressure loss increases due to external wind pressure or the like, the speed of a DC motor 2 increases and a conduction timing control means 10 quickens the switching timing of a conduction phase. On the other hand, when pressure near the discharge port of a duct decreases due to side wind or the like or pressure loss decreases, the speed of the DC motor 2 decreases and the conduction timing control means 10 delays the switching timing of the conduction phase, thus driving a DC motor without using any phase detection element such as a Hall IC and at the same time, suppressing the increase in the amount of wind near an area where static pressure is equal to zero, and suppressing the decrease in the maximum static pressure. |
