ATHDF% or THDFi or current THD

[Anonymous user]

Hi,

Can someone explain to me how bad this figure is for ATHDF%...using a Tektronix power meter PA1000 to characterise a power adapter 230VAC to 5Vdc. The power adapter has a rating of 5V output, max 1A. When loaded at max 1A, the power meter provides a power factor reading of 0.427 and ATHDF% of 154. I'm having difficulty interpreting 154 for THDF(current). 154% looks bad but is it normal for these cheap type switching PSUs? At 25% load or 250mA the reading increases to 163%.

Thanks

[DanL · Accepted solution]

I'm not familiar with the term "ATHDF%" nor the "Tektronix power meter PA1000", but if I had to guess this is the "Amps Total Harmonic Distortion as a % of Fundamental".
Yes, >100% current distortion as a % of fundamental is very typical for all switch-mode power supplies without active PFC. Normally for most loads <50W, load current THD is not a concern.

[Anonymous user]

Great, thanks for the reply. Yes, your guess of the acronym ATHDF% is correct.