|
The rotor variable frequency is to feed in the energy respectively into the Stator windings and Rotor winding in induction motor, which mostly fit with the constant loading manufacturing machines. In some high-voltage, high-power and small speed-regulating range condition, the rotor variable frequency on Asynchronous Motor is often used because of its high reliability, low construction cost and high economic benefit. Moreover, foreign countries have done research on rotor control of variable frequency in a wide rang, and use it gradually in the industrial field, due to its quick dynamic response, low Harmonic Pollution, and H-F energy saving and adjusting power factor in electrical network,.In the control proposal, choose rotor current direction control, and introduce stator current flux linkage component to achieve closed-loop control. Due to rotor current component is vertical with stator flux linkage (the amplitude of stator flux linkage is constant); its current component can achieve decoupling control. The speed-regulation is working under d-q coordinate system of rotor, and takes rotor current component as orientation control, so there is no need to test the initial position of the rotor. Thus forms the speed sensor-less of rotor control of variable frequency system, which enhances the reliability of the system.In the aspect of hardware design, choose AC—AC controller as the basic structure of rotor variable frequency controller, design and debug the hardware circuits focuses on power, trigger control, logic judgment, electrical relay, SCM and other parts. In the aspect of software, introduce numeral integral-separated digital PI controlling algorithm, to increase the system’s reliability; simultaneously, use Cosine Wave Crossing to control the gating angle of AC—AC controller, because the AC—AC controller work in low-frequency condition, in the procedure, under the insurance of accuracy of breaking, some time consuming computing can be done off-line. Integrate debug until the system work normally, actually measure the values of stator current, and then compare the change, analyze the effect on energy saving.The design focuses on controlling the energy saving on rotor variable frequency motor. After analyzing the mathematical model of Asynchronous Motor of ball crusher, steady the speed regulation component of rotor current, adjudge the Reactive Power component to achieve the energy saving effect. Experiment and debug the rotor variable frequency control system, the results prove that the vector control for variable speed system of rotor current orientation has these merits:low power of transducer, high power factor, good dynamic property and wide speed-regulating range and etc., which make the system suit for the controlling of loading speed-regulation of blower, pump and ball crusher, and has a well perspective in the industry. This thesis provides many pictures of experiment to study the performance of the rotor variable frequency motor and established the foundation of the study the rotor variable frequency motor in other aspects.
|