To: meyer
I've had to isolate these type of problems. Any load change induced hum is typically a tuned resonant circuit response in compensating for the load variance. Without getting into the complexities, one sore spot is where I blame manufacturers for going "cheap" in using the power grid as a cost savings crutch. Our grid is very stable compared to Europe (voltage/current phase alignment). Europe requires "power factor corrected" switching power supplies to protect any inductive/capacitive (mainly inductive) shift on their power from modern electronics. In the US, it is cheaper for products to not have this power factor correction circuitry. Thus, these "cutting corner designs" can create localized phase shift feedback issues by a proportional inductive load progression. It's like having a particular "rattle" in your vehicle that you can find by hitting the right rpm.
To: EarthResearcher333
In the industry, it’s typical for large commercial and industrial customers to be charged for reactive power. Loads are almost always inductive, and larger customers will install capacitor banks for correction.
3,496 posted on
05/03/2017 11:58:15 AM PDT by
meyer
(The Constitution says what it says, and it doesn't say what it doesn't say.)
To: EarthResearcher333
As far as the voltage regulation on my UPS, it’s purely electronic so there’s no telling what kind of noise it might be putting back out towards the house.
3,497 posted on
05/03/2017 12:00:23 PM PDT by
meyer
(The Constitution says what it says, and it doesn't say what it doesn't say.)
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