Study on Control System of Inverter-Fed Linear Motor for Urban Transit

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1. It was confirmed experimentally that dynamic operating points of linear induction motor(LIM) for driving a passenger vehicle were on the characteristics curves of steady state. The response of the thrust and the other characteristics corresponding to the supply frequency and voltage vary with the magnitude of the acceleration and the capacity of machine. It was confirmed that there was no problem of the response, in the V/f speed control test without speed feed-back on the test facility of LIM (lOOkVA, 25Hz, 44OV) for urban transit in our laboratory. As the capacity per one LIM is about 300-400 kVA and the maximum acceleration is 3-4 km/h/s in the case of practical LIM-driven subway vehicle, there is no problem of the response even in the practical use.2. It was found that the electromagnetic analysis for steady state could be applied even for the discussion of the dynamic characteristics and optimum operating point of LIM. The results of simulations for the dynamic characteristics … More proved the accuracy of the theory from comparing with measured results. In the simulation, the simplified space harmonic technique with short calculation time, which was proposed by authors, and motion equation considered with inertia of mass were used.3. For the speed control of LIM for urban transit, the slip frequency control is useful, and the complicated vector control is not required. As a determination method of the optimum slip frequency, the following two conditions are useful and make easy to do it, because these limit the optimum region. (a) in the region for optimum (output kW)/(input kVA), thrust/(input kW) and efficiency at each frequency (b) in the region of that the thrust is larger than the required value at rated current, the attractive vertical force is smaller than the limited value at the rated current.4. It was found that the change of characteristics was small for change of the air gap and a lateral displacement even in the case of current control, as a output control of inverter for LIM drive. So, a current source type PWM inverter should be also discussed for power controller of LIM. Less