A calibration system for electric power at frequencies up to 1 MHz

Electrical power measurements are a central part of society today. Traditional power measurements have been focused on the power delivered by the 50 Hz or 60 Hz electrical grid with up to about 50 harmonics. This means that the bandwidth of such a power meter only needs to be a few kHz. Most modern electrical devices and machines are powered by batteries, or by the grid via DC converters. Ironically, measuring power in these devices requires higher bandwidth, because most modern devices use switching power converters, either to convert AC grid power to DC power, or to convert between different DC voltage levels. These power converters work at switching frequencies of several kHz up to several tens of kHz. Higher frequencies means potentially lower power losses, so the trend is towards higher frequencies. Many instrument manufacturers now offer power meters with bandwidth in the MHz range. In order to address the calibration needs for these instruments, we have developed a reference power calibration system for frequencies up to 1 MHz. In this article we describe the system and the procedures for ensuring traceable power measurements.