NINGBO ZHENGUO INTELLINGENT LIGHTING CO.,LTD , https://www.intellingentlighting.com
Fan, pump equipment most of the asynchronous motor direct drive mode of operation, there is a large start-up current, mechanical shock, poor electrical protection and other shortcomings. Not only affect the service life of the equipment, but also when the load appears mechanical failure can not be instantaneous action to protect the equipment, pump damage often occurs at the same time the motor is also burned phenomenon. In recent years, out of the urgent need for energy saving and the continuous improvement of product quality requirements, combined with the use of frequency converter (inverter) easy operation, maintenance-free, high control accuracy, and can be achieved high-functional features; thus using Drive-driven program began to gradually replace the damper, baffle, valve control program. The basic principle of frequency control technology is based on the relationship between the motor speed and the input frequency of the working power supply: n = 60 f (1 -s) / p, (where n, f, s, p, respectively, Motor slip, motor pole pairs); by changing the motor operating frequency to achieve the purpose of changing the motor speed. Inverter is based on the above principles using AC - DC - AC power conversion technology, power electronics, microcomputer control technology in a comprehensive electrical products. Third, the analysis of energy-saving Through the basic laws of fluid dynamics can be seen: fans, pumps are square torque load, the speed n and flow Q, pressure H and shaft power P has the following relationship: Qαn, Hαn2, P Αn3; that is, the flow rate is proportional to the rotational speed, the pressure is proportional to the square of the rotational speed, and the shaft power is proportional to the rotational speed of the cube. Taking a water pump as an example, its outlet pressure head is H0 (outlet pressure head is the static pressure difference between the pump inlet and the outlet of the pipe), the rated speed is n0, the pipe resistance characteristic when the valve is fully open is r0, the rated working condition The corresponding pressure is H1, and the outlet flow is Q1. Flow - speed - pressure curve as shown below. In the field of control, the pump is usually used to run the outlet valve to control the flow rate. When the flow rate decreases from Q1 to Q2, the valve opening decreases and the resistance of the pipe network changes from r0 to r1. The system operating point moves from point A to point B along the direction I. By the throttle effect pressure H1 becomes H2. Pump shaft power actual value (kW) can be obtained by the formula: P = Q • H / (ηc • ηb) × 10-3. Among them, P, Q, H, ηc, ηb, respectively, power, flow, pressure, pump efficiency, transmission efficiency, direct drive to 1. Assuming that the total efficiency (ηc • ηb) is 1, the pump will move from point A to point B, and the motor power savings will be the area difference between AQ1OH1 and BQ2OH2. If the governor is used to change the pump speed n, when the flow rate is reduced by 50% from Q1 to Q2, then the pipe network resistance characteristic is the same curve r0. The system operating point will move along the direction II from point A to point C, Pump operation is more reasonable. In the valve is fully open, only the case of pipe network resistance, the system to meet the flow requirements of the scene, energy consumption is bound to reduce. In this case, the motor consumes less power than the area of ​​AQ1OH1 and CQ2OH3. Compared with the valve opening adjustment and pump speed control, it is clear that the use of pump speed control more effective and reasonable, with significant energy savings. In addition, it can also be seen from the figure that when the valve is adjusted, the system pressure H will increase, which will threaten and destroy the sealing performance of the pipeline and the valve. When the speed is adjusted, the system pressure H will vary with the pump speed n Lower and lower, so will not have a negative impact on the system. From the above comparison is not difficult to draw: When the demand for pump flow from the scene down to 50% from 100%, the use of speed adjustment than the original valve to save the corresponding BCH3H2 power size, energy saving rate of 75%. Similarly, if you use frequency control technology to change the pump, fan speed to control the scene pressure, temperature, water level and other process control parameters, the same can be based on the system control characteristics of the relationship curve drawn the above comparison results . That is, using frequency control technology to change the motor speed than the use of valves, baffles more economical and economical regulation, equipment operating conditions will also be significantly improved. Fourth, the energy-saving calculation For the fan, pump equipment, energy-saving effect after the use of frequency control, usually using the following two ways to calculate: 1, according to the known fan, pump flow in different control mode - load curve and the scene Run load changes were calculated. Taking an IS150-125-400 centrifugal pump as an example, the rated flow rate is 200.16m3 / h and the lift is 50m. The Y225M-4 motor is equipped with a rated power of 45kW. Pump in the valve adjustment and speed adjustment flow - load curve as shown below. According to operational requirements, the pump runs continuously for 24 hours, of which 11 hours a day runs at 90% load and 13 hours runs at 50% load; the annual running time is 300 days.