Yes indeed, the main one being people now using the wrong figures in calculations.
If the UK leaves the EU, will the nominal voltage be changed back to 240v?
- Thread starter eveares
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Yes indeed, the main one being people now using the wrong figures in calculations.
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It is simply impossible for the nominal value to be wrong.
Once more you show us that you really, really, REALLY do not have a clue what you are talking about.
Once more you show us that you really, really, REALLY do not have a clue what you are talking about.
That is essentially true, since it is a arbitrary creation of paper-pushers which has no physical/engineering meaning. If 'they' assert some nominal voltage (whether it be 240V, 230V or 600V) then they can't be 'wrong' - maybe stupid, but not 'wrong'!
However, as winston has said, the true concern is about the use of arbitrary (aka electrically meaningless) voltages for safety-related calculations.
Kind Regards, John
There are multiple acceptable spellings of some words.
That's the way it works.
Get over it.
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Then I declare that the nominal value of the standard single-phase supply in Britain is 600 volts, with a tolerance of -58 to -64%. It's impossible for that nominal value (with the declared permissible tolerance) to be wrong, but obviously it would be absurd to specify it that way.
There are spellings that are acceptable in the US but not the UK. Likewise there are ones acceptable in the UK but not the US. This forum is a UK forum.
And even more absurd to base calculations on 600 volts.
I think you'll find that it is you who is wrong and absurd.
Nobody, or hardly anybody, agrees with your bonkers refusal to accept what "nominal" means, and every time you express that refusal you make yourself look even more stupid than you made yourself look the previous time.
As I keep saying, a lot of the problem seems to arise because, in the case of electricity supply voltages, the word "nominal" seems to be being used in a sense which differs from how it is nearly always used in engineering and many other fields.
To say that a nut, bolt, screw, rod, pipe, tyre, piston or whatever has a certain 'nominal' size has a widely understood meaning. To say that a bag of flour, sugar or whatever contains a certain 'nominal' weight of the product has a widely understood meaning. To say that a tablet or capsule contains a certain 'nominal' amount of the active medicinal constituent has a widely understood meaning. To say that an engine, pump, heater or whatever has a certain 'nominal' output has a widely understood meaning. In none of those cases is there any expectation that the actual measurement/quantity concerned will commonly, let alone 'nearly always', differ from the 'nominal' value stated.
If a bag of sugar were intended to contain 1 kg of sugar, and if the average weight of the sugar in such bags was close to 1 kg, only an idiot would today declare the 'nominal' sugar content as, say, 800g (even if he did also state a 'tolerance'). That would take us back to the pre-E-mark 'bad old days' when it might have been labelled as 'no less than 800g', at great potential cost to the supplier, through fear of litigation (a bit like the baker's dozen!).
Kind Regards, John
ie 12 -0 +1 (nominal) 
That would have been their hope, although there would still have been a finite probability that some customer would end up with only 11 (or 14)!ie 12 -0 +1 (nominal)
Moving back to the present, there is obviously a difference between many of the engineering scenarios (including supply voltage) and matters of consumer product content labelling. Unlike many of the engineering applications, there is usually no concern about the 'upper side' of the distribution with quantities of consumer products, so the regulations are generally asymmetrical. Hence if, for example, a bag of sugar is labelled "1 kg" with an adjacent e-mark, that means that the average contents of bags must not be less than 1 kg, and that no more than a certain proportion of bags will have less than a specified weight of sugar (e.g. 0.95 kg) - the regulations aren't concerned about the lucky customer who might end up with 1.5 kg of sugar
Kind Regards, John
Whereas with electricity supplies, at least in Britain, it was taken that the permissible variation was a symmetrical tolerance about the declared nominal voltage, as in 240 +/-6%.
There are instances of tolerances in electronics work being somewhat asymmetrical about the nominal value, as I'm sure you can think of John. Electrolytic capacitors are a good example, where due to manufacturing constraints it's not unusual to find a component, especially in larger values, with a declared tolerance of something like -20/+50%. But that's because in most applications of such larger value electrolytics we're not too concerned if the capacitance is considerably above what's needed (smoothing capacitors in power supplies, bypass capacitors in cathode/emitter circuits etc.).
There are instances of tolerances in electronics work being somewhat asymmetrical about the nominal value, as I'm sure you can think of John. Electrolytic capacitors are a good example, where due to manufacturing constraints it's not unusual to find a component, especially in larger values, with a declared tolerance of something like -20/+50%. But that's because in most applications of such larger value electrolytics we're not too concerned if the capacitance is considerably above what's needed (smoothing capacitors in power supplies, bypass capacitors in cathode/emitter circuits etc.).
Sure, but that's just like the sugar - just as a consumer is not going to be worried about their "1kg" bag of sugar containing 1.3kg, nor (in the sort of applications you mention) is an engineer going to be concerned about a "100 μF" smoothing capacitor having a capacitance of 120 or 130 μF. There are, of course, countless other electronics situations in which one is equally concerned about positive and negative deviations from the 'intended/marked' value.
Sure. I would imagine that they aim at around 120 μF, and then label it as "100 μF -20%/+50%", for the reasons you mention. Aiming for 100 μF and thereby ending up with a component of, say, "100 μF ±35%" might well be regarded as potentially having too low a capacitance for the application. They could, of course, simply label the usual "100 μF" component as something like "120 μF ±35%", but then user would have to do the thinking
Kind Regards, John
Precisely - There's good reason for the asymmetric tolerance which is often applied to electrolytic capacitors due to the applications for which they're used. But there was no good reason for adopting the peculiar asymmetric tolerance of 230V +10/-6% for mains supplies.
As Detlef suggested earlier, I can but presume that it was thought that, in our case, existing equipment/appliances might not function satisfactorily at voltages below 216.2V (i.e. between 207V and 216.2V), so we needed (a lot of!) time to allow any/all such equipment to come to the end of its natural life before our supply voltage was allowed to be as low as 207V. Similarly, at the other end, some existing equipment in "220V countries" might not be happy with voltages as high as 253V.
Kind Regards, John
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