【正文】 ig. 4. When the flow rate is continuously increased and beyond %, and the frequency regulator reaches its rated frequency 50 Hz, PLC will mand the second motor to connect to the mains again and the third one at standby mode. The operating region of the third one falls within curves 3 and 6 in the Fig. 4. If the flow rate is reduced from % to %, PIX will mand to one of the pump motors cut off from the mains. When the flowrate further reduces, and less than %, 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. CRITERIA FOR FREQUENCY, REGULATOR For the load of the hydraulic pump, the torque is proportional to the square of the motor speed, it is also proportional to the square of the supply frequency, f2. To a electric motor, the torque is equal to Cm *Φm*I2*cosα, where Cm, is a constant, Φm, is the magic flux of rotating field, I2 is the rotor current, and cosα is the power factor of rotor circuit. I2 normally cannot exceed its rated the voltage drop in the stator is negligible, $, will be proportional to supply voltage V. In order to maintain, the supply voltage V should be required to be proportional to the square of the frequency. Therefore, the characteristic of V versus f should be set to be a quadratic relationship. CONCLUSION This type of variable frequency constant pressure closed loop system for water supply was designed and implemented in Shanghai, China. The performance was proven satisfactory. A copy of a photograph of this system was shown in Fig. 5. All four advantages of this proposed system were fully realized. This system is one of the energy saving methods in tall building design. Automation System S7300: Getting Started CPU 31xC: Commissioning 1. Step: Installing the mounting rail and modules Rail installation sequence From left to right: Power supply PS 307 CPU 313C. The synopsis will provide you with an overview of the overall configuration. Install and ground the mounting rail 1. Screw on the mounting rail (screw size: M6) so that at least 40 mm space remains above and below the rail. When mounting it on a grounded metallic panel or on a grounded device mounting panel made of steel sheet, make sure you have a low impedance connection between the mounting rail and the mounting surface. 2. Connect the rail to the protective conductor. An M6 screw is provided on the rail for this purpose. Minimum crosssection from the cable to the protective conductor: at least 10 mm2. Installing modules on the mounting rail 1. Hook the power supply module onto the rail, slide it until it reaches the grounding screw of the rail and then screw it tight. 2. Hook the CPU onto the rail (1),slide it along as far as the module on the left (2), and swing it down into place (3). 3. Bolt the CPU tight, applying a torque of between and Nm. 4. Insert the micro memory card into the CPU (4)。. It in turn means that H at point b is less than that at point b39。 DESIGN AND OF A VARIABLE FREQUENCY REGULATORY SYSTEM FOR WATER SUPPLY ABSTRACT The designs of the variable frequency constant pressure water supply for a single hydraulic pump and high power multiple hydraulic motors systems are presented in this paper. This system can save energy by controlling the speed of the pipe motors which depend upon the number of consumers in use. This system was also uccessfully implemented in most of the modern buildings in. Shanghai, China. Finally, the choice criteria for variable frequency regulators for water supply system will be discussed. INTRODUCTION It is inevitable to install high level water storage systems or reservoirs for a multiple story building or residential areas. This kind of system results in increasing construction cost and cleaning problems. Nevertheless, hydraulic pumps are used to raise the energy level of the water. The conventional high level reservoir system is in fact a pressure regulatory system. This pressure (head) is proportional to the height of the reservoir. Resistance of pipes is varying from time to time. When number of users increases, that means number of relief valves to be open is increased. It in turn reduces the resistance of the pipes. In order to reduce the construction cost, eliminate the cleansing problem of the high level reservoirs, and make the system simple, a variable frequency constant pressure closed loop system is presented to control the speeds of the hydraulic pumps. In this paper, the designs of the variable frequency constant pressure water supply for a single hydraulic pump and high power multiple hydraulic motors systems are presented. From static characteristics of water flow system, the critical point can be obtained to achieve the minimization of energy consumed. The implementation of this system