Digital Storage Soft Starting And Voltage Adjustment Control For Three Phase AC Motor

At present, the AC adjusting voltage technology is applied in many fields, such as AC motor soft start, AC power adjusting electrical heating, motor energy saving controlling, and power system static reactive power compensation (SVC) etc. There are various circuit structures and control methods to realize AC voltage adjustment. The AC voltage adjusting circuit with SCR phase-control plays a dominant role in the industrial AC voltage adjustment because of its great capacity, high voltage rank, small cost and strong reliability etc, in spite of the existence of certain defects. As for the SCR AC voltage controlling methods, many traditional phase-control methods are adopted at present. However, these traditional methods possess the defects of low digital level, large volume, uneasily connecting with other digital equipments, and unsuitably integrated in high performance, and so on. The thesis mainly studies a brand new digital control method for SCR AC voltage adjustment, as well as the circuit topological structure and control problem of the circuit used in the immediate-and-high voltage AC motor starting.On basis of the analysis, conclusion and comparison in the many AC voltage controlling methods, the paper brought up a digital storage softly starting controlling method which applies the high performance C8051F MCU as control core, and designed and developed the main circuit and the software and hardware control system for the three phase AC motor digital storage soft start device. The system is mainly composed of the MCU controlling system, the AC voltage controlling main circuit, key board and displaying unit, and the driving unit etc. The equipment applied the modern high speed data storage technology to write the code produced by programming into the memory in advance. The SCM controls the system output by the address of storage choosing models. The system adopts two controlling methods, including the open loop and closed loop. At open loop model, the system can automatically set the triggering angle to control the motor starting and running. At closed loop model, the SCM adjusts the he value of load and power by comparing the out signal detected from the current transformer with the set rated current, and then chooses the proper controlling model from the storage, in this way to avoid the waste and save the energy. To resolve the soft start for high-voltage motors, we has studied the high-voltage soft starter that is based on the switch-mode transformer, and has analyzed its control performance. According to the experiment testing, the system plan is proved to be reasonable and feasible.