Controlling start of screw compressor to be driven by three-phase motor - measuring pressure produced by rotary movement of screw compressor and stopping drive motor if pressure is in contrast compared to normal pressure

摘要

The pressure resulting between the compressor (1) and a screw chamber of the compressor and a non return valve (11), is sensed in a suction or outlet duct (8; 10) connected directly to it, with the starting of the screw compressor driven by the 3-phase motor (2). The system includes a pressure sensor (18), which is an isolating switch controllable by the effect of the pressure. A switch (5) has a contactor for connecting the motor (2) to the electrical mains, and the control current of the contactor is connected to flow through the pressure sensor (18), so that the pressure sensor under the effect of a faulty pressure switches off the control current of the contactor, which disconnects the motor from the electrical mains. The pressure sensor (18) is adjusted to sense the pressure between the non return valve (11) in the outlet duct (10) of the compressor and the compressor, and the pressure sensor (18) functions, if the pressure fails to reach the atmospheric pressure. ADVANTAGE - Prevents rotation of compressor in wrong direction of rotation reliably, and system is simpler, cheaper and more reliable than known methods and systems.