The first goal of this thesis is to develop a non-intrusive in-situ efficiency estimation technique, which is capable of dealing with unbalanced supplies and under- or overvoltage conditions. For the purpose of this thesis, non-intrusiveness refers to electrical measurements at terminals only, with no mechanical measurements, not even speed. This requirement imposes limitations on the available data, which brings challenges to the efficiency estimation problem. To have the lowest possible intrusion level, only two line voltages and currents are allowed to be measured, and all the required information, such as input and output power, speed, temperature, and the motor parameters, must be calculated or estimated solely based on these measurements. 
The second goal of this thesis is to develop a simple method for full load efficiency estimation from no-load uncoupled testing, which can be used in refurbishment centers to estimate the efficiency of induction machines without performing expensive dynamometer testing.