Power supply quality concerns are the consequences of the increasing use of solid state switching devices, power electronically switched loads, unbalanced power systems, lightning controls, computer and data processing equipment, as well as industrial plant rectifiers and inverters. In this book, special prominence is given to the degrading of power quality due to unbalanced power supply. Moreover, the impact of unbalanced voltage on the performance of three-phase induction motors are also underlined. Three-phase induction motors are broadly used in diverse industrial applications while unbalances in supply voltage are responsible for various ailing impacts on their performance. Furthermore, the variation of performance parameters of three-phase induction motors have been analysed. Additionally, various existing methods for the assessment of the performance induction motor under the supply voltage unbalance have been critically reviewed to underline their shortcomings. The causes, effects, mitigation techniques along with the various interpretations of voltage unbalance, prescribed in different standard, are also discussed to highlight their deficits.