| 摘要 |
PURPOSE: To conduct automatic control of a two-speed DC motor so that a loss of speed, overheat and disconnection of a DC motor be prevented and also that the most efficient operation be used by switching the motor between high-speed and low-speed operation curves at a point of mutual intersection of these curves according to a loaded state. CONSTITUTION: A control switch 104 connects power to a first switch terminal 108 when a low speed of a DC motor 102 is selected and to a second switch terminal 110 when a high speed is selected. A bistable bimetal circuit switcher 116 is connected between these switch terminals and low-speed and high-speed inputs, in order to prevent a loss of speed of the motor at a high speed, by switching between the high-speed input 114 and the low-speed input 112 of the motor 102 according to the state of operation, when the high speed is selected. The switcher 116 comprises current-monitoring bimetal elements 124 and 126 and a bistable switch element 118 responding to these elements, and a switching operation thereof is conducted at a point of mutual intersection of high-speed and low-speed operation curves.
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