A Wide-Range Digital Power/Energy Meter for Systems with Nonsinusoidal Waveforms

A versatile, precision power/energy measurement system is described which is now in use gathering data on electric vehicle drive systems. It was designed to improve the measurement accuracy of systems with nonsinusoidal waveforms. At a continuous 1-MHz rate, it simultaneously digitizes the voltage and current for the input and output of a power converter under test. At the same 1-MHz rate the samples are multiplied together to get instantaneous power, and accumulated. Every half second the accumulations are used to calculate the average input and output voltage, current and power, total energy, amp-hours, and input-output efficiency. When used with coaxial shunts the operating range extends from milliwatts to megawatts. The efficiency measurements are accurate to within a few tenths of a percent for chopper frequencies up to 10 kHz.