Does the PC power supply introduce harmonics into the power grid?
This is a continuation of the article: how much electricity a PC consumes during operation.
This time, an oscilloscope with a current pickup and a differential probe will be used to measure the voltage.
Two measurements were made, the first with the computer running without load, and then with the OCCT program load (in PSU testing mode). The measurements were saved in a .CSV sheet, and then, based on the collected data, an analysis of the harmonics contained in the waveform was performed.
Measurement without computer load
RMS current: 510 mA
RMS voltage: 220V
Apparent power: 110VA
PSU load 16%
Cosφ due to offset of voltage and current peaks: 0.92
Higher harmonic content: THD = 4.56%
The first harmonic (50Hz) has the highest value of 0.71A, the second most significant is the 3rd harmonic (150Hz) of 0.04A.
Measurement with a loaded computer
RMS current: 2820 mA
RMS voltage: 216V
Apparent power: 609VA
PSU load: 47%
Cosφ due to offset of voltage and current peaks: 0.95
Higher harmonic content: THD = 4.7%
The 1st harmonic (50Hz) has the highest value of 2.69A, the second most powerful is the 3rd harmonic (150Hz) 0.17A.
Summary
The difference is significant to the disadvantage of the device without this system.
The course of the current drawn from the mains by the tested power supply can be considered as close to a sine wave, while the level of higher harmonics tested with the FFT Hann algorithm does not exceed 5%, which can be considered a good result.
Notes
Since the first article in this section was written, the configuration of the computer has changed.
The change that most affects the measurement results concerns the graphics card.
Previously it was: EVGA GeForce GTX670
Now it’s: ASUS Radeon RX580
