Abstract: Surge control systems are provided for compressors which supply air to a pneumatic load. A signal proportional to the pressure ratio of the outlet pressure to the inlet pressure plus a selected reference pressure is compared to a measured weight flow rate of air through the compressor to provide a vent valve command signal. If the measured pressure ratio plus the reference pressure ratio exceeds the measured flow rate, a surge condition may ensue. The vent valve position command signal causes a venting valve to vent a portion of the air provided to the load, which reduces the measured pressure ratio and increases weight flow rate. During normal operation of the compressor, the vent valve command signal is zero for all values of weight flow rate. A transient control channel is provided which is responsive to the rate of change of the measured pressure ratio and/or measured weight flow rate.

Abstract: Surge control systems prevent and control a surge condition for fixed or variable speed compressors and compressors having variable geometry which provide air to pneumatic loads. A signal proportional to the ratio of the measured compressor outlet pressure to the measured inlet pressure is combined with a signal corresponding to a selected reference pressure to provide a vent valve command signal. When the signal representing the ratio of the measured pressure exceeds the signal corresponding to the selected reference pressure, a surge condition is developing and the vent valve command signal causes a valve to vent a portion of the air to the pneumatic load. The venting of the air reduces the measured pressure ratio and the vent valve command signal decreases, to close the valve. A signal is provided to reduce the effect of the reference pressure ratio if the weight flow rate through the compressor is reduced, as by decreasing compressor speed and/or repositioning the inlet guide vanes of the compressor.

Abstract: A surge control system for controlling and preventing a surge condition and a method of controlling surge in a fixed or variable speed compressor or a compressor having a variable geometry which provides air to a pneumatic load. A transducer provides a signal proportional to the outlet pressure of the air from the compressor. The signal is differentiated with respect to time and if a surge condition is ensuing, the absolute value of the differentiated signal is greater than a reference. When the differentiated signal is greater than the reference, a portion of the air supplied to the load is vented to reduce the outlet pressure. A reduction in the outlet pressure alleviates the ensuing surge condition and the absolute value of the differentiated signal decreases, causing the venting valve to close.