Technical and Economical Considerations on Super High-Efficiency Three-Phase Motors

Abstract

Premium efficiency motors are now mandatory in North America, but new higher efficiency classes are being introduced. Motors of IE4 Super-Premium Efficiency Class are already available in the market, and a new IE5 Ultra-Premium Efficiency Class is being considered. Within the IE4 Super-Premium Class, line-start permanent-magnet motors (LSPMs) are a recent entrance in the industrial motor market. Its steady-state performance is outstanding, but as in all technologies, there are some associated issues, both for retrofitting or new applications. The LSPM efficiency can be measured according to the input-output (or direct) method specified in the IEEE 112 or IEC 60034-2-1 standards, but if the losses are to be segregated, for example, to allow proper temperature correction, it is important to evaluate if the specified test methods can be applied to this sort of machine. Due to the significant promotion and penetration of variable-speed drives (VSDs) in industrial motor driven systems, the motor tolerance and operation limits to such devices are addressed in this paper. The proposed IEC 60034-2-3 Standard specifies test methods for determining harmonic losses of VSD-fed motors, supplementing the methods intended for operation on sinusoidal supply. In this paper, the referred issues will be addressed in detail, and experimental results on the application of the IEC 60034-2-1 and IEC 60034-2-3 standards to IE2, IE3, and IE4 class motors are presented and discussed, with the focus on the LSPM Super-Premium technology. A comparative technical and economical analysis of commercial IE2, IE3, and IE4 class motors is presented, including an in-field example of replacement of a squirrel-cage induction motor by an LSPM.