Compressor and operation method

Abstract

The invention provides a compressor and an operating method thereof. A switching valve is fixed at the suction side of the main body of the compressor, and lower limit rotation rate of the motor is setted in a control device, wherein the gas volume discharged to the discharging side of the main body of the compressor is approximately same with gas volume leaked to the suction side. When the rotation rate of the motor is in a range above the lower limit rotation rate and below the upper limit rotation rate, a control device determins a control rotation rate for eliminating the bias of the detected pressure relatively to the preestablished target pressure, opens the switching valve when the control rotation rate is bigger than the lower limit rotation rate, and closes the switching valve when the control rotation rate is smaller than the lower limit rotation rate. According to the constructure, the range of the rotation rate control relatively to the volume control can be expanded, and the reflux of the oil to the suction side can be avoided.

Description

technical field [0001] The present invention relates to a compressor and a method of operating the same. Background technique [0002] In general, in a screw compressor, the rotation of the screw rotors pushes out gas on the discharge side, but the gas leaks to the suction side due to gaps formed between the screw rotors or between the screw rotors and the casing. As the rotational speed decreases, the leakage of the gas to the suction side becomes more obvious. [0003] In order to avoid an increase in the leakage of compressed gas to the low-pressure side of the compressor body due to an excessive reduction in the rotational speed of the motor driving the main body of the oil-free screw compressor, for example, the following method is described in JP-A-2002-054578: When the speed is higher than the preset value, the suction regulating valve on the suction side of the compressor body is opened to control the motor speed, and when the speed reaches the preset value, the spe...

AI Technical Summary

Problems solved by technology

The control using the suction control valve has the following problems: the suction control valve must be frequently opened and closed, the mechanical parts such as the valve body of the suction control valve are worn out a lot, and the pressure pulsation is easy to occur.

[0007] However, in an oil-cooled screw compressor, the gas leaked to the suction side moves with the oil, and when the speed drops to a very low speed, the amount of gas leaked to the suction side will be larger than the amount of gas pushed out to the discharge side. As the amount of gas increases, the oil flows back to the suction side, and the suction filter installed in the flow path on the suction side becomes contaminated with oil, resulting in a decrease in the function of the filter and a reduction in the suction volume.

Images