| 摘要 |
PURPOSE:To protect a motor and power transistors for sure by providing a relay contact and a galvanometer resistor and cutting off the current to the motor properly when the current flowing through the resistor rises abnormally. CONSTITUTION:The current IM measured by a galvanometer resistor 6 and the reference current I are ocmpared each other, and when IM>I caused by mingling of foreign objects is detected, it is judged that a motor 5 is locked, and a motor lock indicator IC is activated so as to cut off the motor current. When a motor lock caused by icing or others occurs, it is first judged based on the outdoor temperature whether any possibility of occurrence for a lock by icing exists or not, and if the possibility exists, the current is flown for a certain time except through power tansistors Tr1, Tr2 so as to automatically try to release the icing lock by means of the self-generated heat of the motor 5. If the lock can not still be released, the motor lock indicator IC is actuated immediately to cut off the current so that the motor 5 and the power transistors Tr1, Tr2 are protected for sure. |
