| 摘要 |
A low charge protection method for an electronically controlled variable displacement compressor. In each period of compressor operation, a low charge test sequence is carried out to monitor the system performance once the system control pressure has been reduced below a specified level. In a set-up phase of the test, the compressor is down-stroked to near-minimum displacement for a predetermined time or until the system control pressure rises above a reference level. At such point, the compressor is up-stroked to near-maximum displacement to initiate a pull-down phase of the test. If the system pressure is reduced by specified amount within a reference interval, a failed test is indicated and the count in a nonvolatile counter is incremented. If the pull-down duration exceeds the reference interval, a passed test is indicated, and the count, if any, is decremented. When the nonvolatile count exceeds a specified threshold, the compressor is disabled and further operation is prevented until the count is reset by a service technician.
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