| 摘要 |
PURPOSE:To save power by effectively driving a variable pitch axial flow blower by means of a cage-shaped induction motor. CONSTITUTION:The level to be switched to the high efficiency side set by a level setting unit 20 through a process of finding the efficiency to the output rate in driving an electric motor 13 with a star connection and 10 driving it with a delta connection. Respective electromagnetic switches 25, 26 are so operated that the electric motor may be driven with the star connection by a switching instruction unit 22 when the output detected by a current transformer 16 is less than the switching level, while it may be driven with the delta connection when the output detected by the current transformer 16 is more than the switching level., Thus, the electric motor is always driven with the connection having very higher efficienty out of these connections. |
