Optimum operating point of an induction machine using a rotor integrated converter with a floating capacitor

• Published in: 2016 IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia) pp. 98 - 103
• Main Authors: Yanmei Yao, Sadarangani, Chandur
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2016
• Subjects: floating capacitor; Induction machine; Induction machines; operating range; Reactive power; Resistance; rotor integrated converter; Rotors; Stator windings; steady state model; Torque; unity power factor
• DOI: 10.1109/IPEMC.2016.7512268

This paper investigates an induction machine using a novel concept of rotating converter. The stator is directly connected to the grid while the rotor is fed by a rotating converter with a floating capacitor over the dc-link. An analytical method to find the operating point at specific power factor and torque is proposed in this paper, which is verified by the good agreement between calculation and experimental results. It is found that when the considered machine topology is operated at rated torque and unity power factor, the efficiency can be improved by 0.74% compared with the standard induction machine with short-circuited rotor. Moreover, the effect of reducing the rotor resistance on efficiency improvement of the induction machine at unity power factor is explored. A further efficiency improvement of 2.36% can be achieved by decreasing the rotor resistance by 30%. Furthermore, optimum efficiency of the induction machine is studied when it drives a pump and operates near the rated operation point. The result shows that an optimum efficiency, which is 3.13% higher than the standard machine, can be obtained by operating the machine at a new operation point other than the rated condition. Decreasing the rotor resistance by 30% will further increase the optimum efficiency by 1.47%. The corresponding output power will also increase with higher operation speed and load torque.