The impact of the unbalance in both the voltage and the frequency on the performance of single and cascaded induction motors

• Published in: Energy (Oxford) Vol. 181; pp. 561 - 575
• Main Authors: El-Kharashi, Eyhab, Massoud, Joseph Girgis, Al-Ahmar, M.A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.08.2019; Elsevier BV
• Subjects: Cascaded induction motors; Computer simulation; Copper; Copper loss; Electric potential; Energy conversion; Harmonic distortion; Induction motors; Matlab simulation; Power factor; Studying energy conversion; Torque; Unbalance; Unbalanced voltage; Unrated frequency; Voltage; Unrated frequency; Matlab simulation; Cascaded induction motors; Studying energy conversion; Unbalanced voltage
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2019.05.169

This study focuses on the performance and energy conversion process of cascaded induction motors (CIMs) operated under balanced and unbalanced conditions. In this paper, two mechanically combined induction motors having a similar rating (25 Hp) are investigated for comparing with a large induction motor (50 Hp) — imbalances can occur in the applied voltage, operating frequency, or both. The impacts of both unbalanced voltage and unrated frequency on maximum and steady-state torque, power factor, input active and reactive powers, stator and rotor copper losses, and total harmonic distortion (THD) in voltage and current, have been investigated through a simulated model created using Matlab/Simulink software. This work demonstrates that machine performance and efficiency are improved by introducing more electrical and mechanical advantages of cascading the electrical machines. The results show that the maximum torque of the CIMs is higher than that of a single one at different operation cases; it is increased by 18.4% during balanced operation. The total copper losses are reduced by 36.5% in balanced operation when using CIMs instead of the large motor. Consequently, the energy conversion process and performance were significantly improved. •The paper improves the induction motor performance by using cascaded motors.•Imbalances can occur in the applied voltage, operating frequency, or both.•The total copper losses of the single motor are higher than cascaded motors.•The torque of cascaded machines is always higher than that the single one.•The efficiency is improved when used cascaded machines.