RP-667 -- Measurements of Electrical Power Inputs to Variable Speed Motors and Their Solid State Converters PDF

An increasing number of variable-speed variable-output HV AC equipment units continue being installed because of their high energy savings; however, because of the non-linearity inherent in the semiconductor devices used in these power converters, the voltage and current waveforms supplied to the motors are not purely sinusoidal and thus contain extremely high harmonic contents. Many available instruments do not measure mis distorted current, power or energy accurately due to limitations in the meter frequency response, range, internal impedance, etc.

The objective of this research was to obtain a body of accurate and relative data which can be used to define the instrument type, instrument specifications, and instrument use mat will result in accurately measuring the volts, current, watts and watthours into the solid state power supply and into the motor leads of the variable speed motor systems ranging from 1/2 hp to ISO hp. The accuracy of this measurement should be at least as good and preferably better man traditionally available on analogue RMS power type meters, 0.2% full scale with 2 to 1 scale changes.