Cable size and diversity

[trojanhawrs]

Never assume.

Just me?

Are you saying the current will rise with lower voltage?

I'm saying I don't know how it will behave and those calculations are meaningless.

 

[JohnW2]

I'd be more likely to assume it's given for 230V, that's the european standard.

You probably need to tell that to the marketing people who seem to have almost universally decided that they want the power of their products quoted into relation to 240V, which makes the products sound more powerful than they actually are when supplied with the "European Standard" 230V

 

[JohnW2]

I'm saying I don't know how it will behave and those calculations are meaningless.

If you look for it, documentation will (should) nearly always tell you what voltage the claimed power relates to - and if you have that information, the calculations are correct, not 'meaningless'.

 

[trojanhawrs]

If you look for it, documentation will (should) nearly always tell you what voltage the claimed power relates to - and if you have that information, the calculations are correct, not 'meaningless'.

I thought it was fairly obvious I was talking about the ohms law transposition

 

[JohnW2]

I thought it was fairly obvious I was talking about the ohms law transposition

No, that wasn't 'obvious' (at least, not to me) - so are you saying that you don't believe that an electric cooker (at least, traditional oven, gill and hotplate elements) behaves as a resistive load?

 

[trojanhawrs]

No, that wasn't 'obvious' (at least, not to me)

That's because you've not bothered to read any of the prior posts in this thread.

Post number 1

To sum up, I will be having installed a full Boscfh Kitchen set up:

Oven 2.4Kw
Oven (with microwave 2.8Kw
Induction Hob 7.4Kw
Warming Drawer appraently up to 600Watt (cannot find appliance specific wattage)
Extractor Fan 233 Watt

My first post

I'd be more likely to assume it's given for 230V, that's the european standard.
Either way, induction hobs are far from a purely resistive load (it's in the name) so you can't assume the current drops with the voltage.

 

[JohnW2]

That's because you've not bothered to read any of the prior posts in this thread.

I certainly did 'bother' but, as you point out, I'd forgotten what you had written, for which I apologise.

My first post

I'd be more likely to assume it's given for 230V, that's the european standard.

As I've said, that will very rarely the case, thanks to the marketeers.

Either way, induction hobs are far from a purely resistive load (it's in the name) so you can't assume the current drops with the voltage.

Fair enough - again, I'd forgotten that we were talking about an induction hob. However, since we are, and as you are suggesting, one cannot assume that the current (to the induction hob) will be less at 230V than at 240V. In fact, it may well be higher. So, again, I ow you an apology.

Having said all that, the differences between 230V and 240V will be fairly small (in either direction) and (in the sort of context we are discussing) only really of concern to those obsessed with 'strict adherence' to regulations.

 

[trojanhawrs]

@JohnW2 No worries - agreed it's not a major issue I just thought it's worth pointing out that you can't make calculations based on a resistive circuit

 

[JohnW2]

@JohnW2 No worries - agreed it's not a major issue I just thought it's worth pointing out that you can't make calculations based on a resistive circuit

Indeed - at least, one can't undertake calculations based on such a (probably incorrect) assumption if/when one remembers that one is talking about an induction hob (or anything else else which is 'probably non-resistive')

 

[fixitflav]

Indeed - at least, one can't undertake calculations based on such a (probably incorrect) assumption if/when one remembers that one is talking about an induction hob (or anything else else which is 'probably non-resistive')

As was discussed on here a while back, with an electric motor (normal induction type) with varying voltage the power stays very nearly constant so the current varies inversely

 

[JohnW2]

As was discussed on here a while back, with an electric motor (normal induction type) with varying voltage the power stays very nearly constant so the current varies inversely

True - although I don't think many people would accuse a motor of being a 'resistive load' However, I would have thought more important, domestically, is the fact that the same is generally true of any of the countless things which use SMPSUs.

 

[fixitflav]

True - although I don't think many people would accuse a motor of being a 'resistive load' However, I would have thought more important, domestically, is the fact that the same is generally true of any of the countless things which use SMPSUs.

Thinking about it a bit more - with a pure inductance (or capacitance) the impedance is constant at a given frequency, so the current varies directly with voltage. I'd guess that applies to an induction hob but not 100% sure.

 

[plugwash]

Afaict it's not practical to build an induction hob where the actual induction part runs at 50Hz, a much higher frequency is needed for effective heating. So an induction hob is an electronic load, and it's voltage/current characteristics will depend entirely on how the control electronics behave.

 

[JohnW2]

Thinking about it a bit more - with a pure inductance (or capacitance) the impedance is constant at a given frequency, so the current varies directly with voltage. I'd guess that applies to an induction hob but not 100% sure.

That would be true for a purely reactive load, but such a load would presumably not consume any power!

As plugwash has implied, the point about induction hobs, as with anything fed through an SMPSU, is that the (input) voltage/current relationship is totally dependent upon the electronics - so anything is possible. Those electronics could make the current constant regardless of input voltage, could make current increase with diminishing input voltage (hence maintaining power), or anything else. In the case of an induction hob, there is the additional complication of 'current limiting'.

 

[morqthana]

However, I would have thought more important, domestically, is the fact that the same is generally true of any of the countless things which use SMPSUs.

Like induction hobs, I believe?