The economics of energy efficient motors during unbalanced voltage conditions

This paper discusses potential energy savings opportunities by using energy efficient motors. It investigates the steady-state performance and economics of both standard and energy efficient motors when fed by an unbalanced supply voltage. In this study an advanced electrical model that accounts for the skin effect in the rotor bar to predict motor impedance is used to predict motor performance and calculate motor losses during unbalanced voltage conditions. Different motor sizes are studied and a simple economic evaluation method is presented. The study shows both standard and energy efficient motors are adversely affected by unbalanced voltage conditions. It is noted that energy efficient motors exhibit higher rotor losses and starting current but offer better economics compared to standard motors