I have 2 PPP recently purchased used from different sellers and different countrys. Both advertised as functioning 100% and from a general point of view they seem OK.
My problem is that BOTH are exhibiting the same behaviour simultaneosly and i dont know how to fix this.
They both switch into protection mode (simultaneosly) at random times of the day for a few minutes and then back to normal. When this happens i managed to notice that THD rises to 6% - 7% when its normal value fluctuates between 2.5% - 3.5%.
It seems the PPP is switching to direct wall power when the THD rises above 6%. Is this normal ?
Also, i notice a toroidal mechanical hum from within the PPP and also from speakers when this is happening. As if the AC noise travels through the PPP and through my amplifier into the speakers, when THD is high and emmits noise.
I read some users reporting using the PPP in 5%-6% input THD normal values and no problems.
The values of THD i am referring to are INPUT.
The OUTPUT THD values usually are at 0.7% when in normal AC ( with 3% THD input).