Winding Asynchronous Motor Rotor Current Chopper Speed Control System Design

Wound-rotor induction motors are used in large amount of cranes and air blowers in our country, and are controlled in discrete steps and open loop. The technology can not follow the step of modernized technology developing. Because the voltage of the rotor side of the wound-rotor induction motors is far lower than the stator side. So the way based on current chopper is a economical and practical method in some situation.The paper probes into the rotor current IGBT chopper control system for induction motor. In this paper a novel chopper circuit consisting of elements: commutation bridge, micro-controller, one IGBT, one diode, one resistor and one electrolytic capacitor is presenter. Experiments and simulation have shown that the circuit can not only adjust the current in the rotor circuit efficiently, but also absorb the spikes across IGBT when the switch is turned off, and the turn-off track of IGBT can be improver a lot. The value of the resistor and capacitor can be determined according to the design method giver in paper so that the specified speed ratio can be achieved and the power spikes across IGBT when it is turned-off can be weakened or avoided. For the double-loop speed control circuit, the system gives a further simplified and improved program .The system core based on STC12C5410AD makes the design of current chopper controller to acquire rotational speed. And it achieves a closed-loop feedback control of rotational speed. And it gives the current and rotational speed double-loop speed control system architecture block diagram, the preparation procedure of the control system for the soft-start and soft-parking. In our system, the stator voltage control is also applied as a secondary strategy, so that the motor can also run at low speeds with light load. The practical calculation method of the stator voltage has also been introduced.In this system, we applied micro-controller as the fuzzy controller. Based on the control object, we employed the "adjustable factors of fuzzy control rule" to realize the software control method and normalize the circuit to decrease the cost and enhance the reliability of the system. What's more we can accomplish complexer control. Finally MATLAB modeling and simulation curve shows that the system design is feasible. Experimental testing results show that the system with a IGBT rotor chopper controlled circuit structure is reliable and practical.