https://rvelectricity.substack.com/p/diy-generator-bonding-p...
I think the quality of your power is determined mainly by the size of the transformer serving your neighborhood as well as the presence of noisy heavy power equipment like AC with poor/no soft starters or big brush motors among the consumers. It's noticeably worse on our street compared to where we previously lived.
This generator is meant to back up a 400A electrical service that runs a 480V 200 HP three-phase water pump motor, which draws ~225A and is controlled by a VFD. This pump motor and drive run just fine on utility power, but when utility power was cut to let the generator drive the pump, the generator output frequency started jumping between 57-63 hz and a manometer placed on the generator showed the gas pressure fluctuating wildly.
Now, a 480V 250kW generator puts out (250000/480/1.732)=300.712 amps, which should be more than enough to run the pump. I asked the generator manufacturer what size generator they would recommend for this 200 HP pump, and they said for a basic 6-pulse VFD, it would need a 350kW generator with a 600kW alternator, but the existing generator could be used if a harmonic filter was added to the variable frequency drive.
I don’t really understand exactly what the issue was, but something with impedance and harmonics that could be corrected with a harmonic filter, and once that harmonic filter was added, the generator was able to run the water pump just fine.
How does that happen? Let's say it's running and I drop the input to 80 volts. Why do I get any behavior that isn't "runs at reduced capacity" or "shuts off"? And what part of the circuit is failing?
Are we assuming a combination of missing current limiting and a heavy load? If I'm just watching youtube then it shouldn't overload any components even if it keeps running at a really low voltage.
Same facility was fed 3-phase power, but due to some construction mishap nearby, one leg was cut. That lost us a lot of expensive power supplies that day for some of the more expensive equipment.
Those are examples, but not really an answer to the how question. I'm not an electrical engineer, so :shrug-emoji: I asked the engineers that question at the time, and they told me it was something along the lines of the equipment tried really hard trying to function instead of just shutting off. The dip was low, but not that low. Described like a ceased electrical motor where it keeps pulling more power where normally a breaker/fuse would trip, but something different. It wasn't a satisfactory answer then any more than it is now.
For a voltage drop, the main idea that comes to mind is something trying to keep up a constant wattage and drawing increasing current to make that happen. But you have to do quite a bad job to design that circuit and not have a current limit.
And a PC power supply is inherently flexible on the input voltage, so it would never have the problems you get with a fixed ratio transformer on that old equipment.
From all of that, I have learned the lessons of how dips can ruin electronic equipment (even if not the exact why back then), so for me and my house all electronics are hooked up to a UPS or power conditioner. Appliances are on their own though as that's the landlords problem! Multiple times a week, I get noticeable dips where the lights visibly dim and I can hear all of the UPS units kick in and back to mains a few seconds later.
But, certainly, garbage devices are all over the place.
under voltage can do lots of things. Browning out with partial functionality can cause lots of problems. Some devices will pull about the same watts regardless of input voltage, so lower voltage means more current, and significant under voltage may require much higher than rated current and can damage connectors, leading to thermal runaway (loosened connector has more resistance -> more current -> more heat -> connector loosens). Brown outs during control sequences can lead to controlled loads running for longer than intended and over current situations too.
It typically shows up ‘randomly’ unless you know how to attribute it.
Class D amplifiers and other topologies that depend upon SMPS for power delivery are usually unaffected. Class A/B is where you will typically hear it.