| From the view point of engineering application, this thesis implements the PLC cascade speed regulation control system of logic control, time control, counting control and sequence control based on the crisp analysis and thorough research of high-voltage motor cascade speed regulation control system. PLC is the core control element l of the cascade speed regulation control system.By adopting S7-200 PLC-CPU224 as main unit, the automatic control, the action logical function of cascade speed regulation system is realized, and friendly human-machine interface is developed. The following works have been done: according to the system status transfer diagram, using sequence control instruction to implement the process control. That is to say, the system status transfer beween startup, stop state, speed regulation status and full speed state, and the operation of contactors at the transfer process. In addition, calling the subroutine in the mainline program, to implement the speed adjustment, chopped control based on PWM output function of PLC, analogue data acquisition and process, water resistance control and to acomplish control mode switching.Firstly, this thesis researches and analyses the working principle of internal feedback chop-wave cascade speed-regulation system. And based on above analysis the hardware selectinon and PLC control program design of the PLC cascade speed regulation control system are developed. Including concretely: engineering control requirement analysis, system analysis, overall design of the control system, reliability design of the control system, and software design. Then build the experiment system to debug and test the control program. Finally, to realize setup and on-line modifying of system parameter, including protection setting value, work mode, the lowest speed, the highest speed of the motor, the rate of ascending/descending, and to implement the display function of the system running status, control mode, running parameters and alarm information. |
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