EASA AEMT Study of Motor Repair Impact on Efficiency of Premium Efficiency (IE3) Motors

In response to various opinions about the feasibility of maintaining motor efficiency during repair, including replacement of the stator winding, the Electrical Apparatus Service Association (EASA) and the Association of Electrical and Mechanical Trades (AEMT) conducted two comprehensive rewind studies using third-party testing laboratories. The results of the first study, which were published in 2003 (The Effect of Repair/Rewinding on Motor Efficiency. Electrical Apparatus Service Association, 2003), clearly showed that the efficiency of energy efficient and IE2 motors ranging from 7.5 hp to 200 hp (5.5 kW to 150 kW) can be maintained (and sometimes improved) if the stator is rewound using established good practice procedures. The increasing use of premium efficient motors mandated by various countries led to a second rewind study in 2019, this time to determine if the efficiency of premium efficiency and IE3 motors can be maintained when they are rewound using the good practices described in the 2003 rewind study and ANSI/EASA AR100–2015 (Recommended Practice for the Repair of Rotating Electrical Apparatus. Electrical Apparatus Service Association (EASA), ANSI/EASA AR100, 2015). As with the 2003 study, the results of the 2019 rewind study of premium efficient and IE3 motors ranging from 40 hp to 100 hp (30 kW to 75 kW) clearly indicated that the answer was affirmative—with the average efficiency change for the entire test group falling within the range of accuracy for the test method (± 0.2%). This paper addresses the test methods, methodology, test results, and technical details of the 2019 rewind study.