4.3.3.1 Efficiency – First article testing to determine the efficiency of the unit shall measure the following per IEEE: a) Copper Losses (I2R) (calculated value) b) Core Losses c) Stray Load Losses d) Friction and Windage e) Exciter Losses (slip rings or a suitable means of measuring exciter voltage and current are required) The following efficiencies shall be determined: a) 100% Load at 0.8 pf b) 75% Load at 0.8 pf c) 50% Load at 0.8 pf