Influence of NEMA T Rerate Program on Integral Horsepower Motors for the Petroleum Industry

Factual information is presented to show that rerate T-frame motors offer users substantially more value than motors of prior vintage. The gain is not alone a matter of size-weight reduction nor the obvious economic one of avoiding, in industrial ac motors, the inflationary price spiral that generally afflicts American manufactured products. Gains are also evident in: insulation life expectancy, bearing load capability or bearing minimum fatigue life, thermal margin in the bearing lubricant. Through improved computerized design techniques, these gains are achieved without sacrifice in motor efficiency; design level of power factor is slightly lower for T-frame motors, but in-service power factor is generally improved over previous U-frame motors because the T-frame units are designed to a more realistic voltage standard.