I have a 4000/6600 Watt (continuous/surge) gasoline powered generator for use as emergency back up power for my house. Its output frequency at low or no load is about 62.5 Hz. With about a 2000 watt (typical) continuous load the frequency will settle down to 61.5 Hz. Voltage is fairly stable, varies from 116V to 122V depending on load. Scope confirms this. Waveform is a relatively clean sine but shows some harmonic content and noise. I’m with the understanding that these specs are typical for portable generators.
It would seem to me that being off by Hertz or two shouldn’t be too much of a concern. These days nearly everything has a switch mode power supply in it. Such power supplies aren’t fussy about the line input frequency.
I tested some older (possibly sacrificial) electronic equipment like a lap top and small flat screen and they work just fine on genny power, as I figured they would. But I’m still hesitant to hook up the “good” TV or desk top computers to an AC source that isn’t rock solid. Both desktops have UPS’s on them. The UPS’s do NOT like being connected to the generator even when adjusted to be more tolerant of utility line fluctuations. If the generator power can freak out my UPS’s what might it do to my other stuff?
Yes, I know I could avoid all this with an inverter type generator. I looked at that option and decided it wasn’t worth the money considering how likely it will be used.
The UPS almost certainly doesn’t care per-se, it’s just that they’re designed to detect problems in the supply and under normal conditions you get very close to a perfect 60 hz sine wave and within a few volts of 120. It sees deviations as an indication of a faulty source.
But almost nothing else will care. As you mentioned, switch mode power supplies are almost universal and work on a wide variety of sources. This includes your TV and computers. Resistive loads won’t be affected by these minor fluctuations. A synchronous motor will change speed slightly, but you probably don’t have one of those. It might affect some clocks in your house if they’re using line frequency to keep track of time.
Basically, don’t worry about it. The UPS is designed to be more sensitive. The irony is that they’d probably freak out if you plugged one into another, since their own output is usually pretty shoddy.
IDK, but I have 2 generators in that same ballpark as the one you mention and never hesitated to use everything in my house during a power failure (except for things the generator couldn’t run as it doesn’t have the power, such as central air). TV’s, laptops, smart home devices and appliances. They don’t seem to mind and I have had several week long power outages running on it.
Yeah, if the UPS detects a lot of ripple or over/under voltage it is designed to scream and turn on. If you are really concerned about a delicate power supply or piece of equipment, get a battery ‘generator’ with ‘true sine’ output like Bluetti or EcoFlow and use your generator to charge that.
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I also built a box to monitor the voltage and current put out by the generator when it is powering the house:
Nice! You can monitor L1 and L2 voltages at the same time, good to let you know if you have an unbalanced load.
Remember, it is the UPS battery that powers your connected devices. It’s flow is steady even if the flow it is receiving from the AC is fluctuating to some extent. Part of the UPS makeup is to let you know when the AC is varying from the norm from complete AC failure all the way down to minor fluctuations, so its going to appear more dramatic than it actually is.
