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1 overview In industrial enterprises, the motor is to apply the most extensive and one of the largest number of electrical equipment. Currently, a large number of AC motors are working at a fixed speed operation, it has become increasingly unable to meet the requirements of production technology for automation. At the same time, its running in low power factor and low efficiency of the condition, and a great waste of energy. As the petrochemical industry increasingly fierce market competition, our factory model of petrochemical products, quality, quantity and put forward new demands. In order to meet the requirements of these processes, in the original drive motor to increase the inverter system. This will smooth the amount change in the delivery of materials to meet the requirements of the production process, but also to achieve energy-saving effect. Regular line in our plant, often used in the second inverter system is not only power source is changing the process parameters of the implementing agencies, which replaces the previous executive body - regulating valve so that control of media transfer process occurs the change. 2 inverter speed adjusting of energy principle In the actual production process, various options are greater than the pump load the actual needs of production flow, while in actual operation, the flow rate is often much smaller than the design flow, if not used in motor speed , can only be controlled by adjusting the flow valve, the results of the valve will cause great loss of energy. If you do not have the valve adjustment, but to run the motor speed, then, when you need traffic is reduced, the motor speed reduction of energy consumption will be significantly reduced. Figure 1 shows a typical pump load at different speeds of the characteristic curve. H (n1), H (n2) said the governor when Q = f (H) curve, R1, R2, said regulating valve when the piping resistance curve. Valve control, due to the reduction of traffic, off a small valve, the valve of friction became larger, Q2 Q1, A B, HA HB valve control power consumption of the P1 by the 0HBBQ1 said. When the speed control when, Q2 Q1, A C, HA HC speed control power consumption of the P2 by the 0HCCQ1 said that if P1> P2, said speed control valve when the throttle when power consumption is less than the power consumption. P = rQH pump shaft power Q r liquid flow severe head H Points in B and C point of run-time PB-PC = Q1 (HB-HC) r This part is the energy savings. The pump load, the following expression: Q1/Q2 = n1/n2 H1/H2 = (n1/n2) 2 P1/p2 = (n1/n2) 3 From the above equation, when the speed dropped 1 / 2, the flow rate down 1 / 2, pressure drop 1 / 4, Power down 1 / 8, that power and speed into 3 power relationship between the decline. If the valves do not close down small way, but the motor speed down, then with the pump output pressure of reduced flow in the same delivery, the original power consumption of the valve can be completely avoided. Not loaded inverter, the pump discharge flow control by adjusting valve. Traffic hours, by the relevant small valve control, pump control pressure increases, so that part of the energy consumption in the export valve in vain. After using the converter can reduce the pump speed, pump head was correspondingly reduced, the motor output power is also reduced, thereby eliminating the original consumption of the pump control valve on the pressure. 3 Inverter Control System I often plant and regular first-line pumps B109 B114 II pump motor power was 75kW and 55kW, speed 2982 r / min, rated voltage 380V, rated current, respectively 132A and 103A, respectively, rated the export flow To 28.520M3 / h and 20M3 / h. Shown in Figure 2. Can be seen from the chart, in the normal load condition, the electrical work in the rated speed 2982rpm, speed is not adjustable. In order to maintain steady flow and method of using export controls to control valves, differential pressure transmitter that is detected flow signal sent to the PID regulator, and then by the PID regulator output 4-20mA control signal to control the export control valve opening, to control the export flows to maintain flow stability. The original system operation, the following problems: (1) section of a larger flow, pump outlet valve section flow is close to half of the pump rated flow, waste a lot of power. (2) control the accuracy of low volatile export flows (about 3%). (3) electrical work in the rated speed, output unchanged consumption of energy. (4) noisy motor, pump and pipeline valve pressure more easily lead to leaks. According to the system of the technological requirements, our design of the inverter system, follow the following principles: A, to maintain stable export flow; b, export flow control accuracy 0.5%; c, the motor speed range from 0 to 2982 should be transferred / min; d, according to the pump's performance characteristics, system design should be constant torque principles; e, energy saving; f, system design uses a dual-frequency and frequency switching to ensure continuity of production and reliability, mutual backup; g, using two DCS output contacts, the way the original valve control the way control the inverter, the inverter fault state, DCS will automatically identify frequency fault signal, and then switch to regulate the flow control valve. When the converter is in normal operation, the control valve in the fully open position; Accordance with these principles, through research, comparison, we chose Toshiba A5P inverter. The inverter has advanced technology, complete function, compact structure, high reliability, for pumps and fans load design. The chart shown in Figure 3. FRH: frequency settings; ACC / DEC: Add / deceleration control circuit; A / D: analog-digital Converter; V / F: voltage-frequency transformation; BD: base drive circuit; CPU: microprocessor; LED: display circuit. Inverter main circuit for the typical "pay? Straight? Pay" SPWM voltage main circuit. Inverter control circuit: frequency of a given FRH (ie the speed to be) through the ACC and the DED acceleration and deceleration control circuit, into a frequency and voltage reference signals, respectively, through the A / D converter circuit and V / F function generator circuit, and then into the CPU, the formation of SPWM pulse, as IGBT control signal, driving IGBT, so that a constant voltage, constant frequency alternating current, through the frequency converter into a voltage adjustable frequency AC. A5P converter chart shown in Figure 3. The whole control system is sampled by computer, computing, real-time control, accident alarm and display. 4 converter system operation 1997 7 months, I plant in the regular line of pumps and pump motors often two to install Toshiba A5P inverter, the operation compared with the frequency as follows: (1) motor operating parameters and energy saving by comparison Saving power = ((39.16 × 0.82 × 380 I am an expert from carreplacementkeys.com, while we provides the quality product, such as China replacement car key , automotive key blanks, car key blanks,and more.
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