Abstract. This paper presents, based on experimental tests, an analysis of the effects of unbalance voltage on temperature rise of three-phase induction motor (TIM) with a view to evaluating effectiveness of the method of measurement employed, namely the method of symmetrical components. To do so, one motor is subjected to conditions of unbalance, strategically chosen, and their elevations of temperatures measured in three-phases are displayed. Among the many results obtained, it was found for voltage combinations where the voltage unbalance factor (VUF) has values very close to 0%, the existence of temperature rises higher than those where the VUF is greater than 2%. From investigations made, it is concluded that the use of VUF as single and sufficient index for the quantification of voltage unbalance is inappropriate.