| 摘要 |
PURPOSE:To heat and thermally insulate a motor while stopping operation thereof, by storing and specifying a frequency lower than an operational frequency range to a circuit for storing a switching pattern necessary for the operational frequency of an inverter. CONSTITUTION:Power from an AC power source 2 is rectified 3 then the rectified power is fed to an inverter 4 to produce AC power for rotating an induction motor 5 with a predetermined rotation. A CPU 10 provides a digital voltage command signal S1 and determines an upper address in a ROM 14 thus providing a frequency command signal S2. A rate multiplier 12 multiplies the signal S2 based on an output S3 from a clock 11 and produces a signal S4. The signal S4 is binary counted 13 and lowermost data S6 are outputted as a latch signal for a waveform synthesizing circuit 15 while other data S5 are outputted as an address signal for a memory 14. Frequencies lower than a normal operational frequency range are set in the memory 14 and selected based on the signal S1. Consequently, the motor is heated and thermally insulated while being stopped of its operation, and such device can be preferably employed in a compressor being operated in cold area. |
