Compressor surge detection system

Claim 1

In a compressor system including a compressor driven by an electric motor, a surge detection system comprising the following combination: means for sensing the motor current to derive a current representative signal; means responsive to said current representative signal for sampling over a sliding window a plurality of successive and consecutive samples thereof; means for deriving one sample at a time as an instantaneous representation of the motor current magnitude; means responsive to said plurality of samples for continuously deriving therefrom and through successive windows a signal representative of the average thereof; comparator means responsive to a threshold signal and to said sample average for detecting a polarity signal representative of an excess in magnitude above and below said sample average; means responsive to said polarity signal and to said one sample for detecting the occurrence of successive polarity changes in said polarity signal as an indication of an impeding surge; and means for generating a surge indicative signal to be applied to the compressor system when said polarity changes have lasted during a predetermined time period.