Study On The Soft Starting And Saving Energy Technology For Three Phases Induction Motor

Three phases induction motor, which is an important component in manufacturing process, so that its starting, stopping, saving-energy and protection are always the challenge to the researchers. With the development of power electronics and computing technique, the electronic soft starting system for three phases induction motor is made progress, which becomes the preferable technique for dealing with starting, stopping, saving-energy and protection for three phases induction-motor, and the technique has wide applying prospect and development space.In this paper, inherent starting characteristics of three phases induction motor and the features of single phase AC adjusting voltage circuit with inductive load were analyzed, based on which the work states of thyristor three phases AC adjusting voltage circuit and the conversion of these work states due to different trigger angle were summarized. Simulation research about the mode of soft-starting with current or voltage as controlling object was made, after that novelty simulation model aiming at resolving the problem of PID constant current controlling and Fuzzy constant current controlling, and a checking-full-voltage algorithm is presented.The advantages and disadvantages of several prior methods of three phases induction motor to control decompressing and saving energy were compared, and through theoretical analysis and experimental verification, preferably saving energy mode with least stator current as the control variable was gained. Upon discussing the change of current of motor when the induction motor was in broken-phase starting and in broken-phase running, it put forwarded a broken-phase protection measure which combined static broken-phase protection with dynamic broken-phase protection, and makes research of protective principles about short circuit, block-up, over loading and voltage fault.The hardware circuit of three phases induction-motor soft starting system was designed. The problem of extracting synchronizing signal of the system was solved by means of the advantage of the ideal phase-locked loop characteristics, frequency control and narrow-band tracking and as a result, real-time tracking of the synchronizing signal of three phases power supply was realized. It adopted the mode of high frequency trigger pulse with 8253 as hardware basis, which guaranteed the reliability of SCR triggering, and it designed Static broken-phase discrimination circuit which promoted the reliability of the motor. This paper fulfilled software system of three phases induction motor soft starting system, implemented the control of soft starting, soft stopping and saving-energy of the motor and implemented dynamic protection for each fault of the motor. Upon analyzing potential disturbing source of the system, corresponding anti-jamming measure was provided.Qualitative analysis and quantiative calculation of the system reliability of three phases induction motor soft starting system was made by using fault tree analysis(FTA) method, and some measures to improving system reliability was bring forwarded according to the result of the analysis and calculation.