type C rcbo's

[park1]

Does anyone have any decent links to adiabatic calcs. I have done them before but there is more to them than first seen.I have searched for I2T graphs from manufacturers MCBs before but the graphs (if there are any) tend to be rather sketchy.

I realy need to get to the bottom of this. The adiabatic is not as simple as people seem to think.

If you just stick to what is in BS7671 then you will be fine, the Adiabatic err's on the side of caution.

 

[Nicky Tesla]

If you just stick to what is in BS7671 then you will be fine, the Adiabatic err's on the side of caution.

yes.........BS7671 says the adiabatic equation is for triptimes <0.1 seconds

I guess that means you cannot show a worked example

 

[Sidewinder]

Nicky,

I can't write a complete lecture on this in one hit.

First quick thing.

Not having a go at you or anyone else BTW!

Adiabatic Process - That which occurs without any heat exchange with its surroundings.

It is a basic thermodynamic "process", it is NOT specific to electrical engineering.

It is in Chemistry, Physics, Thermodynamics and other branches of science and engineering.

Are you with me so far, look up Adiabatic Process on Wikipedia, I "think" the description is OK.

I'll look at it too over the next few days and if you have any questions on this then these can be sorted first?

Any use?

Mods, would it be worth moving this to a separate thread?

I'm not promising a lecture in 2 days, but part of my Masters was Thermo so I should be able to work this through, IF you are patient with me fitting this in with everything else?

 

[Nicky Tesla]

Adiabatic Process - That which occurs without any heat exchange with its surroundings.

thats why it is only for times of <0.1s

Sides......waiting with baited breath

 

[Sidewinder]

Yes Nicky it will apply to times < 0.1s, but not only to times <0.1s.

Think of the heating affect of the current "in" the conductor itself, during short time periods, and, how quickly this can dissipate into the "ambient" thus re-establishing the status quo.

This "could" be more than 0.1s, however, in such a short period this would be guaranteed.

With greater depth of information and consideration, it could be shown that adiabatic conditions could exist for much longer times than 0.1s

Do you agree, or not?

 

[Nicky Tesla]

yes........i guess for less hot conductors or conductors in a cold environment.

 

[Sidewinder]

Delta T is more important than absolute T, as the "energy transfer" is greater with a larger delta T, you follow?

 

[Nicky Tesla]

is that working stable temperature range and maximum at the brink of melting temperature?

 

[Sidewinder]

No it is the absolute temperature of the cable at the point of the fault occurring in K, the ambient surrounding absolute temperature in K, and the difference between the two, i.e. the delta, not sure if I can post Greek characters, but it is capital Greek Delta, the triangle symbol, it means difference in engineering, scientific and mathematical terms.

Thus the larger the difference in temperature between the cable at the point of the fault occurring and the disconnection time and the relationship between these temperatures and the surrounding environment into which the energy transfer occurs.

e.g. cable running temperature, 293K, surrounding air temperature 293K, no delta T. Fault occurs, cable temperature increases to 303K ambient still 293K, very little delta T, i.e. 10K

 

[Nicky Tesla]

Every mathematician knows it is impossible to understand an elementary course in thermodynamics.

Just found this quote..........but ye i get you

 

[Sidewinder]

Don't know the quote, and it just shows how dull mathematicians are TBH.

I know a cracking quote, but it has to be word perfect to work.

I can remember the gist of it, but not the exact wording.

I'll have to practice it, and post it later.

OK< so you are with me on the Thermo argument so far?

Can you quote me the Zeroth law as a favour, and explain it so I can see that you are with me?

 

[Manator]

Nicky,I can't write a complete lecture on this in one hit.

First quick thing.

Not having a go at you or anyone else BTW!

Adiabatic Process - That which occurs without any heat exchange with its surroundings.

It is a basic thermodynamic "process", it is NOT specific to electrical engineering.

It is in Chemistry, Physics, Thermodynamics and other branches of science and engineering.

Are you with me so far, look up Adiabatic Process on Wikipedia, I "think" the description is OK.

I'll look at it too over the next few days and if you have any questions on this then these can be sorted first?

Any use?

Mods, would it be worth moving this to a separate thread?

I'm not promising a lecture in 2 days, but part of my Masters was Thermo so I should be able to work this through, IF you are patient with me fitting this in with everything else?

I think this thread could withstand the extra debate as it is related and constructive. The outcome of this debate may result in a new thread based on the constructive use of decent and factual debate.

 

[Sidewinder]

The "zeroth law" states that if two systems are at the same time in thermal equilibrium with a third system, they are in thermal equilibrium with each other.Drawn from my dark past, don't asks for formulas though :slap

Not you paddler, you muppet!

Nicky!

Go on Nicky bite his freaking head off! (quote from "Little Nicky", or is my memory failing as usual!)

Oh and you're wrong by the way.

Or at least in the way I understand your wording.

Another limitation of this medium of communications I suspect!

 

[Nicky Tesla]

The zeroth law states that if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.

Basically, heat tranfers around each other. If the third system was not in equilibrium it would effect the second system and so on and temperature would rise.........a bit short but i dont want to waffle plus its bed time:z but i do appreciate it just wished it was earlier

wooah.........when did all those posts happen

 

[Nicky Tesla]

WOT NO CALCS..........I MUST BE RIGHT!!! :Salute

 

[Sidewinder]

Eh?

 

[Nicky Tesla]

Eh?............Telling me about delta T and talking about Zeroth law, is NOT showing how a Type C is not suitable

 

[Sidewinder]

Now Mr Tesla, you have jumped about 100 steps from where we were to that statement.

I did say one thing at a time.

Please explain in your own words the Zeroth law and assure me you understand this then we can move on.

"One step at a time Sweet Jesus" as the song goes

 

[Nicky Tesla]

is that necessary?.......i already have, but do we need to, to do the calcs?

 

[Sidewinder]

I don't believe you have, adequately, sorry.

Once we get past this point then we can investigate going further.

I did say it would be a gradual process.

If you can't wait, tough, sorry, but that is he end of it.