| 摘要 |
PROBLEM TO BE SOLVED: To simplify structure and improve incorporation work, by making it possible to heat refrigerator oil without installing a crank case heater. SOLUTION: This control equipment converts electric power supplied from a power source PS to specified controlled three-phase AC power, outputs it to an induction motor CM, pulse-width-modulates the supply voltage to the induction motor CM, and controls a power converter circuit 20 in such a manner that the induction motor CM is subjected to variable speed control. On the other hand, when a preheating signal is receive during halt of the induction motor CM, the control equipment outputs one phase supply voltage out of the supply voltage to the induction motor CM, as a pulse-width-modulated voltage signal, to the induction motor CM, and outputs the other two-phase supply voltage, as a continuous voltage signal of the same phase square wave AC which is not pulse-width-modulated and held at a specified voltage, to the induction motor CM. As a result, heat is generated without rotating the induction motor CM. |
