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Tests Show Mass-Produced Copper-Rotor Motors More Efficient Than Nameplate Claims
Siemens’ “Above NEMA” Motors Are Also Cost-Competitive Sure enough, the motors that SEA modestly lists as “Premium Efficient” models sport nameplate efficiency ratings that exceed NEMA Premium levels. For example, the NEMA Premium nominal efficiency for a 10-hp, 208-230/460-V, 1800-rpm, general-purpose TEFC motor is 91.7%. SEA’s new versions of this motor, designated GP100 or GP100A (for cast iron and aluminum frame models, respectively) claim a full-load nominal efficiency of 92.4%, or 0.7 percentage points higher than NEMA limits for this size and type. Details can be found on the SEA specification/data sheets for the GP100 and GP100A motors. Other copper-rotor, ultra-high efficiency motors are listed in the company’s index. 
That’s all well and good, but NEMA permits a statistical deviation from its nominal Premium Efficiency ratings to take into account the variations that unavoidably occur under mass-production conditions. Thus, in addition to the nominal rating, NEMA Premium motors’ nameplates also generally identify a guaranteed minimum efficiency rating, which is lower than the nominal value. CDA Tests Actual Efficiency Values 
In order to determine how well SEA’s new motors actually perform, CDA purchased several units from a distributor and submitted them to laboratories for evaluation according to IEEE/ANSI 112-1996, the accepted U.S. test method. (An essentially identical standard applies in Canada.) One of those motors, a 10-hp GP100A, was sent to Advanced Energy, a nationally accredited independent laboratory located in Raleigh, North Carolina (www.advancedenergy.org). Advanced Energy’s lab was the first in the nation (1997) to be accredited for motor efficiency testing by the National Voluntary Laboratory Accreditation Program of the National Institute of Standards. Advanced Energy is well known in the industry. Tables 1 through 3 contain the results of their investigation. Variation in efficiency and power factor as functions of rated power are shown in Figure 2. 
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