230V/240V Question
- Thread starter M1AK
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Ignore this. I answered my own question.
... but the actual wording is even worse than that. It doesn't specify the acceptable voltage range "when frequency is within the acceptable range" - it specifies the acceptable voltage range when the frequency is "at" its 'nominal' value.
Kind Regards, John
Absolutely certain. However, you might call it "mathematical pedanticism", since it is only the "exactly" word which makes the statement true. The probability of an individual value from a Normal distribution being 'very close to' the mean of the distribution is high.
Think about this ... if one expresses the frequency to an 'unlimited' number of decimal places, then there is an infinite number of values it could take, even over a small range (e.g. 49 - 51 Hz). That means that the probability of any individual item from that Normal distribution having any one of that infinite number of possible values (just one of which infinite number of possibilities is 'exactly 50') is infinitely small (aka 'zero'). Nor is there anything special about the mean (50) - the probability of the actual value being exactly equal to any value (e.g. 50.00123456) is also infinitely small.
However, again, as above, this is of theoretical relevance only. Get rid of that word 'exactly' and the probability of the frequency being 'very close to 50 Hz' is very high, not zero! Even the probability of the frequency being 'incredibly close to 50Hz' is high. It's only "exactly 50 Hz" which causes the theoretical mathematical issue.
Kind Regards, John
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No, because the allowable variations in voltage would vary as the frequency varied, and vice versa, so there could be a specification for the allowable variation in voltage but it would be unnecessarily complex.
But the probability of an individual sample taking the mean value is greater than the probability of it taking any other value.
I suspect this is really just an example of badly drafted legislation by Whitehall bureaucrats who really didn't understand the subject but were given a quick briefing on the basic voltage and frequency limits and told to "write it into a regulation."
Not exactly the mean value. As I've just written the probability of a random variate which is part of a true Normal distribution taking any exact value is infinitely small, even if that value is at, or close to, the mean.
Are you one of those people who believes that (1, 2, 3, 4, 5, 6) is a less likely result of the Lottery than any other set of values!
However, it was you who brought up the issue of my understanding of Statistics, so I'm giving you the strictly mathematically correct answers - which, as I've said, all arise from this word "exactly". In practice, your statement above can be made to be correct by simple modification - i.e. "the probability of an individual sample having a value incredibly close to the mean (defined, if you like - e.g. "within 10^-1000000 of the mean") is greater than the probability of it having a value further from the mean".
Kind Regards, John
It wasn't just now.Indeed so - that is the iumplication of the regulation, and the very point I'm making ...
That's surely ridiculous because, as the regulation is worded, in the absence of that "unnecessarily complex" specification, the permitted voltage variation at frequencies other that "at nominal" is not defined. If they wanted to avoid that "unnecessarily complex" specification of permitted voltage variation, they surely should have written it with no mention of "at nominal frequency"?
Kind Regards, John
It wasn't spot on 50.000
That's quite possibly the explanation but the result is that, in terms of "what it actually says" (a well-known phrase around here!), it defines permissible voltage variation only AT nominal frequency. Even if one forgets the "mathematical pedanticism" and interprets that "at nominal frequency" as meaning "at frequencies incredibly close to nominal", that still leaves permitted voltage variation undefined for the rest of the ±1% permitted variation in frequency.
Kind Regards, John
No, because if the frequency were not mentioned, the voltage tolerance could not be measured precisely and repeatably.
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