Note that all manufacturers do not use the same test technique for measuring efficiency. As a result, ratings stamped on the nameplate can be misleading. The National Electrical Manufacturers Association has recommended that U.S. manufacturers follow a standard procedure for measuring efficiency to assure that a comparison of motors will be meaningful. A number of manufacturers use the test method recommended by NEMA (IEEE Standard 112, Test Method B). While this method is more complicated and expensive to apply, it is also more accurate.
It is important to note that foreign manufacturers use different test methods which in most cases do not yield the same results as those obtained by measuring efficiencies in accordance with NEMA's recommendation because they do not include all of the losses. In fact, experience has shown that the three techniques most widely used by foreign manufacturers consistently over-state efficiencies.
