The Research Of Solid-state Soft Starter Based On MC9S12 Micro Controller Unit

This text researches the three-phase asynchronous motor soft starter principle and control method, compares kinds of control ways and emphatically research the torque closed-loop control Aiming at pure integrator in torque estimate u-i model caused the error of integral initial value and dc offset, giving the method of improvement, get relatively accurate real-time torque, realizing the torque closed-loop control. Designs soft starter controlled by single-chip microcomputer MC9S12DG128.In order to avoid the nonlinear characteristics of the rectifier diode influence the accuracy of feedback signals, it takes advantage of the precision rectifier circuit as the analog signal acquisition circuit; To get the synchronization signal by using PLL, frequency separation and phase division function, avoid the false synchronizing signal get by three-phase synchronous transformer when loss phase. Other hardware circuits of matching the single-chip microcomputer make the system more reliable.Built the system simulation model and the control module with the MATLAB/Simulink and did the simulation study. The result verifies the typical control mode and shows the feasibility and superiority of the torque closed-loop controlled soft start system proposed by this paper. The soft starter based on voltage regulation technology using torque control can effectively improve the starting torque, but in high pressure and large capacity asynchronous motor overloaded starting drag still couldn't meet the requirements, this paper introduces the methods of discontinuous AC-AC frequency conversion applied in soft starter on doesn't change the circuit topology, introduces methods of unbalanced voltage decomposition and thyristor control strategy in frequency conversion soft starter system, laid the theoretical foundation of variable frequency soft starter development.