Induction motors lifetime expectancy analysis subject to regular voltage fluctuations

The behaviours of induction motor, even the lifetime, are strongly depending on the power supply quality, such as voltage sags, harmonics and voltage unbalance. The winding temperature increase resulting to insulation breakdown has been considered as one of major causes of the motor failure. This paper investigates the lifetime impact of voltage fluctuations on induction motor, particularly the induction motor operating lifetime reduction which is contributed from stator current variation characteristic. Additionally, the induction motor lifetime expectancy analysis with different load level is also represented subject to two voltage fluctuations conditions, which is (1) constant voltage magnitude change with different modulation frequency. (2) flicker level P
_st
= 3 with different modulation frequency. (3) different voltage magnitude change with different modulation frequency. The demonstration results show the decrease of induction motor lifetime caused by voltage fluctuations is considerably depended on voltage change, modulation frequency and load level, and this reduction tendency cannot be indicated by the flicker index P
_st
value. Thus, one advanced power quality (PQ) index need to be proposed to specify the impact on electrical equipment originated from low frequency voltage distortion.