| 摘要 |
PURPOSE:To ensure the protection of a compressor and improve the reliability even under low load condition by controlling a variable speed of a compressor operation frequency in response to discharge temperature. CONSTITUTION:A heat pump type refrigeration cycle is constructed by coupling into an annular shape a compressor in which the number of revolutions is varied in response to an operation frequency, a four-way valve, an indoor heat exchanger, a pressure reducer, and an outdoor heat exchanger, etc. Discharge temperature is detected by a thermistor 1, and the discharge temperature N and a predetermined set value ND are compared by a microcomputer 2, and a control signal is outputted. With the control signal a variable speed of the operation frequency of the compressor 4 is controlled by a variable frequency unit 3. Hereby bubbling of compressor lubricating oil is eliminated even at the time of rapid lowering of low pressure upon long term stoppage starting and upon long piping starting. And hence the compressor is protected.
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