| For the numerous population in our country, much energy is consumed every year. In recent years, less and less regeneratable energy have affected the industrial production and people's life from time to time. Therefore it is to guarantee industry and life to stabilize a crucial measure of development that energy saving falls to consume. However, since long-term, our country falls behind with the more technical more horizontal more relative comparison of water profession, automation level is low , since user often appears with the instability of water, is using water peak-hour , hydraulic pressure is lower , the supply of water is measured below demand , has too low hydraulic pressure, especially high-rise user regular appearance and can not use the condition of water. The traditional method of solving is to adopt upper cistern and water tower with the various jars of atmospheric pressure retain water pressurization, the resistance that relies on baffle and valve regulates discharge. However, these method or automation level is low , energy is lossed , pressure change big, or because defending workload big, it is polluted that water quality gets easily and have been superseded step by step. This paper has higher physical features according to the field district many sub-districts of moral nature and the daily use of little high-rise resident that built in recent years use water problem,it also have designed a set of water supply system of frequency control of constant voltage based on PLC , and have developed good operation management interface using Supervision Control and Data Acquisition.The water supply system of frequency control of constant voltage changes by PLC, frequency converter, unit, electrical cupboard and pressure to send ware and work, control machine etc. composition. This system is formed by 4 pump generators, 3 main pump generators form the circulating run mode of frequency conversion. With general frequency converter realize for three-phase pump generator soft start with frequency control, operation switch adopts the principle of " start first stop first ". Another little pump generator adopts the run mode of constant speed, make system in water consumption low very much , can stop all main pumps , mend water with little pump , reduce little systematic power comsumption and noise. The detection signal of pressure sensor of hydraulic pressure, via PLC with set value by carry out PID comparison operation, so, control frequency and the export voltage of frequency converter, and then the rotational speed that changes pump generator come to change water supply quantity, eventually, it is nearby to maintain pipe net pressure to stabilize when set value. Through work control machine the connection with PLC, with MCGS group form software consummately systematic monitoring, have realized operation state development to show and data , report to the police inquiry.In operation course, existent frequency conversion directly turns the switch course of work frequency, system very possibility because of current exceptional make the tripping operation of circuit breaker, cause to switch do not succeed. Exceptional switch current and torque will also damage generator , reduce generator service life. The theoretical analysis when this paper turns work frequency according to the rate generator of great merit in frequency conversion, lead into lock appearance ring technology, when switching , frequency and the phase of the lockin export voltage of frequency converter make frequency converter export power source and the work same frequently same appearance of electrical network of power source , and then cut off the power source of frequency conversion, turn pump to work frequency electrical network , can so surmount the current phenomenon in switch course efficiently. Have realized the rate generator frequency conversion of great merit to turn the steady switch of work frequency, decrease for generator equipment damage with the impact of electrical. |
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