AC power calculations include voltage, current, and phase for high-frequency signals. In an inverter-driven machine, the switching frequencies can be at 10s of kHz, while the motor is driven by a fundamental frequency in 100s of Hz.

While the fundamental and its harmonics are the main contributors to real power, the high frequencies will contribute to the reactive power and RMS values by the mathematical definition.

When calculating values like RMS V/I or reactive power, it is critical to account for the frequency content to achieve the definition of RMS/Q in which you are interested. If you include the entire harmonic spectrum of these signals, you may see RMS/Q values that are significantly higher than expected. Many instruments will consist of filters at arbitrary values, making it hard to compare results across locations.

In this free webinar, HBK’s Mitch Marks outlines the definition of reactive power, including RMS values, fundamental values, and filter selection to achieve the desired result. The expert also presents an example showing the effect of filters on P, Q, S, RMS V and RMS I.

Key topics and takeaways:

• Reactive power definitions
• Filter and bandwidth effects on RMS and reactive power
• Harmonic content
• Fundamental measurements