Impact of Frequency Fluctuations

[lonesouth]

I've googled every which way and come up short. What are the potential impacts of frequency fluctuations in power supplied to a home? I understand the impact on inductance motors, they will run slower at lower frequency and faster at higher frequency. What about everything else? Electronics with power supplies? I'm guessing that they almost all rectify the power into DC and step the voltage for the required task, like in a TV or computer, in which case I'm guessing it wouldn't care if it were 60hz or 1hz. Or are there sensitivities in these power supplies impacted by frequency? How far off from 60hz can it go without facing detrimental results? Again, this is for stuff you would find in a typical home.

I've seen the standard listed around 60hz +- 5%, = 57-63hz

 

[Guyfang]

1. Clocks run off. Too low, run slow.
2. Run a motor at too slow a freq, it gets hot and could burn up.
3. Power supplies do not like the freq to be "abnormal".

There are some smart guys here who can explain it better then me. But more then a few freq's out of whack, is not good.

 

[DieselAddict]

If you are within +/-5% you aren't going to do damage. That is a 10% total window. A good running MEP will be WAY inside that range.

 

[Triple Jim]

Well said, Chris. A lot of modern electronic gear, including computers, can deal with wider swings than that, but it would be smart to consult the manual if there's a specific device in question. Induction motors or even synchronous motors aren't terribly picky either, but you don't want to go excessively low, or you risk heating problems.

On an ignition system test bench in my shop, I regularly run a standard 3-phase 1/3 hp induction motor as high as 120 Hz, using a variable frequency drive, to get double the rated motor speed. I also go as low as about 6 Hz for low speeds, but the drive automatically reduces current at low frequencies to keep from overheating the motor.

 

[Daybreak]

Howdy,
In the United States, power is 120/240 volts, and 60Hz.

UL = Underwriters Laboratory
Things which are sold to consumers in the US have a UL sticker. That means it was subjected to variables to qualify for a UL rating. The official UL rating means the product can withstand a variance of 5 %. Most manufacturers do not want to cut it to close and actually test there products to a 7.5% variance to ensure when they submit the product it passes.

Variance is just that. It might work, but it can shorten its lifespan. The preferred is 60Hz. Motors will start easier and better when given 60Hz.

 

[lonesouth]

thanks for the info, especially the UL rating, that clears things up a bunch.

 

[Isaac-1]

This topic has came up over on the Smokstak generator board and it seems that some people have experienced problem from frequency regulation even being just slightly off the 60 hz standard. Most commonly they seems to happen in devices with relatively simple electronics. A couple of cases that come to mind are furnace controller that would not operate properly when powered by the home standby generator, and also a case where a microwave oven in an RV would not reliably operate when powered by the RV generator, but would work when plugged into shore power. As I recall dissection revealed the cheap microwave was using the line AC for its electronic logic timing circuit. In my experience these sort of electronic circuits tend to be found in devices that are primarily AC electrical, but have some type of crude low power digital display and no true DC power supply, often just a bridge rectifier and a resistor custom sized to drop the resulting DC voltage to an acceptable range.