Reliability and operation of high-efficiency induction motors

Mandatory regulations worldwide are being adopted by several countries to accelerate the motor market transformation toward Premium/IE3 and Super-Premium/IE4 efficiency classes. However, besides the motor energy efficiency, there are other important operation issues in the scope of the modern industrials plants which also have to be taken into account when deciding for a high-efficiency motor, such as motor reliability, protection, maintenance, reactive power, operating speed, starting torque, and torque-speed capability. In this paper, key considerations on the reliability and operation of high-efficiency motors are presented, offering a comprehensive perspective on the advantages, drawbacks and limitations of high-efficiency industrial motors. A comparison of the lifetime expectancy of IE2-, IE3- and IE4-Class motors under unbalanced and distorted voltage supply is presented. It is also demonstrated how moving to a higher efficiency class can avoid investing in a larger motor. As far as the authors know, this is the first time this analysis on different classes of very high-efficiency motors is presented.