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10 months ago in Power Electronics By Jennifer

How do you measure power factor for linear vs. nonlinear loads?

I know power factor is cosφ for simple loads. But plug in a computer or LED driver, and that formula doesn't work. How do you actually measure PF for both linear and nonlinear loads?

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By Meera Answered 7 months ago

For linear loads (motors, heaters), PF is just the cosine of the phase angle between voltage and current—displacement PF. A simple wattmeter, voltmeter, and ammeter give you the numbers. For nonlinear loads (rectifiers, SMPS), current harmonics create distortion PF. You need a digital power analyzer that samples instantaneous voltage and current, computes true RMS, and calculates True Power Factor = Real Power / Apparent Power. The meter handles the harmonics; you just read the result. One formula doesn't fit all. The meter does the heavy lifting.

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