Bill Finley and Tyler Gaerke
Siemens Industry, Inc., Norwood, OH

There is always a need to push to higher and higher efficiencies. This can be seen in the revisions to IEEE 841 which pushed efficiencies up to NEMA premium levels. DOE has continued to pass legislation increasing efficiencies to higher levels up to 500 HP. There has also been action recently to establish higher minimum efficiency levels on machines as large as 2500 HP. Motor manufacturers have been motivated to find creative ways to increase efficiency levels through optimization of manufacturing processes, designs, active material increase and better more efficient materials such as magnetic sticks.

To better understand the steps required, it is helpful to understand, how losses are generated and to identify the levers that reduce these significantly, all at an acceptable cost for the investment of the motor. Life cycle costs should also be investigated. 

This paper investigates the impact on the motor performance during starting and normal operation by employing magnetic wedges versus non-magnetic wedges and other potential design changes. The type of induction motor, open (ODP, WPII) or enclosed (TEFC), along with the number of poles, influences the effect on the motor these design changes may have.

Magnetic forces (stresses) acting on the wedges are also investigated in this paper. This paper also discusses qualification processes that are necessary in order to avoid failures and ensure reliable magnetic wedge systems.

This paper covers:

• Designing and testing for NEMA and IEC premium efficiency levels
• History of high efficiency standards activities
• Industrial facility opportunities
• Magnetic wedges (purpose)
• Impact of magnetic wedges on motor performance
• Experimental data for different magnetic wedges
• Qualification of magnetic slot wedges
• Designing with magnetic wedges

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