designandimplementationofavariablefrequencyregulatorysystemforwatersupply-外文文獻(xiàn)-全文預(yù)覽
【正文】 tem for water supply are 1. In a 3 hydraulic motors system, the capacity of the variable frequency regulator is just onethird of the capacity of the overall system. The cost is much reduced. 2. Since the system consists of multiple pumping motors, they can be controlled by PLC such that the system is more reliable. 3. Energy saving can be achieved by controlling the speed of pump motors, pressure can be kept constant no matter what water flow is (from zero to its maximum capacity) 4. Each pumping imotor can be started smoothly by using this variable frequency regulator, it reduces pulse current. This kind of water supply system could bee a new trend in modern multiplestory building design. PRINCIPLE OF OPERA,TION The principle of operation was initially illustrated by a single pump system. Fig. 1 shciws a block diagram of a variable frequency constant pressure system which is suitable for single pump or small scale water flow system. The model type is . The pressure sensor (PS) transduces the water pressure in pipes to e1ect:rical signal. This signal will go to pressure regulator (PR) through an amplifier (A) and a parator pared with the set value of water pressure. The difference will e to the PID control to regulate the output frequency as well as the speeds of electric motors and hydraulic pumps. The constant pressure can then be ac:hieved. Fig. 2 shows static chairacteristics of this constant pressure water supply system. Curves 1 and 2 represent relationship between the pressure head (H) and flowrate (Q) for different speeds of the pump. Curves 3 and 4 represent for different values of resistance of pipe. To simply the exposition, per unit values are adopted in the F39。. It in turn means that H at point b is less than that at point b39。0, there will be only one motor connected to the mains. From the working principle, the three pump motors are operated in turn to meet the requirement of (energy saving. H* 1 Q* L Fig. 4 : Static Characteiisicts of the MultiPumps Water Supply System. CRITERIA FOR FREQUENCY, REGULATOR For the load of the hydraulic pump, the torqu
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