No abstract

This paper proposes a fully digital current control method with DSP for the vector control of the induction motor.

No abstract

The equivalent circuit of the linear induction motor (LIM) is generally expressed as the same that of the rotating induction motor (IM). Then, the starting performance of the LIM is obtained using results of the no-load test and the lock test similar with the IM.However, it is almost impossible to perform the no-load test for the LIM in the factory, because it needs a special equipment to move the mover at synchronous speed. Therefore, a new method is required to calculate the performance of the LIM by simple tests without the no-load test.In this paper, we propose a new method which does not need the no-load test for the starting performance calculation of the LIM. At first, the results of the no-load test and the lock test for the test machine are shown. And an equivalent circuit which is suitable for the performance calculation of the LIM is proposed. Moreover, a method of determining its constants from results of the lock test is discussed. The starting performance calculation for the LIM was made using the proposed equivalent circuit. The calculated results for the thrust vs. speed, the current vs. speed and the power input vs. slip characteristics were satisfactorily agreed with experimental results.

In the vector control system using the slip frequency control method, the rotor resistance of an induction motor is used to calculate a slip frequency. Thus the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic. This paper presents a new method of compensating for the rotor resistance change which is robust for the stator resistance change. A current control loop is composed of the λ‐δ axes in which the λ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved, particularly in the low‐speed region. The experimental results of the current response and the compensation for the rotor resistance deviation also are shown. Moreover, although the mutual inductance has been treated as an invariable value, the value does change by a frequency and an exciting command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no‐load running condition. Furthermore, in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance are shown.