DIGITAL MEASUREMENT OF THE EFFICIENCY OF INVERTER INDUCTION MACHINES

The voltage and current signals representing the electrical power input into the motor are stored in a suitable storage oscilloscope with built-in computing capability. The power input is calculated by multiplying the appropriate voltage and current signals and integrating over one cycle. The mechanical power output is obtained from a standard strain-gage type torque meter. The ratio of the output-to-input power yields the efficiency. The instrumentation to implement this scheme with an overall measurement accuracy of the order of ± 1.0% is described, along with a discussion of the theory behind the digital sampling technique. Finally, the results obtained are presented. © 1990 IEEE