Capacity control device and capacity control method for screw compressor

摘要

An object of the invention is to provide a capacity control device of a screw compressor capable of restraining the consumption of components such as a suction throttle valve and of extending the life of the components. According to the present invention, there is provided a capacity control device of a screw compressor which controls a suction throttle valve by a controlled pressure at which a load operation state is switched to a low pressure operation, and by a minimum operation pressure at which the low pressure operation is switched to the load operation, the capacity control device being characterized by comprising: a pressure detector 15 which detects a discharge pressure of the compressor 1; and a control device 16 which calculates a cycle time between the load operation and the low pressure operation on the basis of the measured pressure detected by the pressure detector 15, and which changes the controlled pressure to a high pressure side when the cycle time becomes not longer than a shortest period specified beforehand on the basis of the life of each component.