Allowed range of the 60Hz mains frequency

Would rather have the frequency running too high rather than too low.

60 Hz equipment should easily be able to handle 70 Hz but not 50Hz or lower necessarily. Can be very hard on things being too low.
Reply to
boB
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** Rediculous nonsense.

The frequency constantly wanders above and below the nominal 60Hz by about 0.1 Hz so the average value over a long period is exactly 60Hz.

** Wot a annoying bloody idiot you are.

..... Phil

Reply to
Phil Allison

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** Step down transformers (and auto transformers) have long been widely sol d to enable folk to use their 120V / 60Hz items in 240V countries where the supply frequency is 50Hz.

Of course they do not change the frequency to 60 Hz and there is no warning about this. SMPS do not care but iron transformers do and may be run heavi ly into core saturation at the lower frequency. The effect is the same as r unning the transformer with the supply voltage increased to 144V.

.... Phil

Reply to
Phil Allison

That's a more reasonable statement than some people's claim to the effect that the 24-hour average is *exactly* 50/60Hz.

I knew about the principle of compensating between peak and off-peak times but I wonder to what degree of precision it's done, especially in earlier times. I don't expect that the frequency is kept at 49.9000Hz during peak hours and at 50.1000Hz for the same period at off-peak. It must drift a bit up and down.

Suppose, over the part of a day during which the frequency is low, it spends x minutes at 49.9Hz, y minutes at 49.953Hz, z minutes at 49.918Hz, etc. ad infinitum. Is it practicable to compensate for the aggregate of those variations precisely enough when the frequency can be raised >50Hz? After all, a clock time base needs to stay within something like 10ppm averaged to be even reasonably accurate.

Maybe they have a clock synced to mains frequency, compare it to an atomic clock, and change the frequency until the mains-synced clock has caught up? It wouldn't be difficult to do that automatically. But no one here has come up with that as an explanation. There's also the question of how much priority is given to mains-synced RTCs.

Reply to
Pimpom

*"Exactly"*?

And a good day to you too, Phil. :-)

Reply to
Pimpom

Pimpom total ignoramous puked

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** Look the word up - you ridiculous, wog troll.

** Piss off, wanker.
Reply to
Phil Allison

Why not? All they have to do is keep track of the cycles and play catch-up each day.

I remember in college I was building a digital clock and was trimming it by looking at the 60 Hz output and the 60 Hz power line using the X-Y inputs. The waveform would wander a bit until I tweaked it carefully to lock in a stable pattern. After a couple of minutes I would see it start to wander again, so I'd tweak it the other way. I did this several times before I realized if I didn't tweak it at all it would wander the same way. I was chasing an unstable reference.

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Rick C
Reply to
rickman

So are you saying that the long-term frequency average is maintained at 60.0000 Hz or better? That much precision is needed to run even a reasonably accurate clock. My $5 watch does better than that.

Reply to
Pimpom

I know. I was baiting Phil. I mentioned the possibility of catch-up in another post. But I also mentioned the question of how much priority is given to it, especially in earlier times.

Reply to
Pimpom

Yeah, like you *need* to bait Phil...

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Rick C
Reply to
rickman

Except that today they maintain the tolerance tighter most of the time. It takes exceptional load conditions to pull it that far out (shortage of generating capacity no wind or sun and coldest winters day).

It is always drifting around the target as demand shifts around. If you want to see it really drift big time watch the realtime frequency monitor around the time of a World Series advert break (or half time at a Wembley final). The grid has to ready itself for such massive loads as everyone puts a 3kW kettle on at more or less the same time.

Yes. Indeed the inventor of the synchronous motor clock gave away his clocks to utility companies to encourage them to do this.

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In Europe a control monitoring group in Switzerland tells the utilities what to do based on a control point at 8am to keep network phase time synchronised to UTC on a long term basis. Long term mains frequency is in effect phase locked to an atomic clock by this final stage.

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Regards, 
Martin Brown
Reply to
Martin Brown

Pimpom wog idiot puked:

** Get cancer & die you wog shit.
Reply to
Phil Allison

My, you seem to be in good form today. Been wrestling crocodiles in your backyard again?

Reply to
Pimpom

It's not just mechanical clocks, LM8560 based LED clocks are also mains disciplined.

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This email has not been checked by half-arsed antivirus software
Reply to
Jasen Betts

But then nobody like LED clocks did they, especially when they were on your wrist and you had to give it a flip or push a button to see it! LED crap!!! A horologist's nightmare!!! Get it off me! Get it off me!

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Rick C
Reply to
rickman

And before that nixie tube based discrete logic ones.

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Regards, 
Martin Brown
Reply to
Martin Brown

We had a benchtop nixie tube DMM where I worked in the early 70s. It was my first encounter with a digital instrument and I was awed by it.

Reply to
Pimpom

Wrong (as usual). I have several LED clocks around the house and I wear an LED watch every day (and night). They're quite popular these days, with annual sales in the tens of millions.

Reply to
krw

Most people aren't such pedants. Your complaint is similar to the furor, here, over JL's latching relay's "infinite" gain.

It's not hard to make it arbitrarily precise. Integrate the number of cycles over any time period you choose and correct that for the ideal. Of course, a power outage sorta screws everything up but that's what they make "atomic clocks" for. ;-)

Sure. Just count cycles and divide by time.

Just could cycles and divide by (atomic) time, or solar, or whatever you choose as your "absolute". Measuring isn't the difficult part.

Reply to
krw

The way it works is they count the cycles over a 24 hour period compared with atomic clock timing. It's not a matter of holding the line frequency at exactly center frequency. That isn't done. That would make it too hard to sync generators and the like but instead by counting cycles over an atomic clock period they know if they need to add cycles or remove some so that electric clocks read correctly. The reason for counting cycles is you need to know how many cycles you have to have produced to get all clacks to read correctly LONG TERM and by that I mean for years and years (though more likely at some time your power will be off and you end up resetting your clocks.) But IF your power never went off your clocks though not precisely correct at any given instant will maintain a certain accuracy long term and will not slowly drift off from minor frequency errors.

Reply to
benj

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