Experimental implementation of minimum losses controller for induction motors
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Date
2026-06-23
Authors
Καρβουνιάρης, Δημήτριος
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Abstract
This diploma thesis investigates the development, simulation, and experimental validation of a loss-minimization speed control strategy for squirrel-cage induction motors. The work was carried out at the Laboratory of Power Systems, Renewable and Distributed Generation of the Department of Electrical and Computer Engineering, University of Patras.
Induction motors are among the most widely used electrical machines in industrial and commercial applications due to their robustness, reliability, and low maintenance requirements. Despite these advantages, their efficiency can be significantly affected by operating conditions, particularly under partial-load operation where unnecessary magnetization levels lead to increased losses. For this reason, improving the efficiency of induction motor drives has become an important research topic in modern electrical engineering.
The theoretical part of the thesis presents the fundamental operating principles of induction motors, including their steady-state and dynamic models, torque production mechanism, and speed–torque characteristics. Particular emphasis is given to indirect field-oriented control (IFOC), which enables independent control of the flux-producing and torque-producing current components. Furthermore, an analytical loss model incorporating copper and iron losses is developed and used as the basis for the implementation of a loss-minimization controller (LMC).
Based on the derived loss model, an optimization procedure is formulated to determine the optimal d-axis and q-axis current references that minimize the total controllable machine losses while satisfying the required torque demand and the operational constraints of the drive system. The LMC control strategy is implemented in MATLAB/Simulink and evaluated under different speed and load conditions. Its performance is compared with that of a field-oriented control (FOC) scheme.
To validate the practical applicability of the LMC approach, an experimental test bench was developed using a Typhoon HIL real-time control platform, a three-phase induction motor drive, and a loading machine. Experimental results obtained under identical operating conditions confirm the effectiveness of the LMC controller.
The obtained simulation and experimental results demonstrate that the loss-minimization controller successfully reduces the total machine losses while maintaining satisfactory speed tracking performance. Compared with field-oriented control, the controller operates with a lower magnetizing current and achieves improved efficiency without compromising system stability or dynamic response.
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Keywords
Squirel cage induction motors, Field oriented control, Loss minimization controllers, Inverters