Someone explain a volt drop.

[vxxbcks]

This is why "Volts" are more correctly referred to as potential difference.

Surely Volts is simply the si unit of potential difference??

 

[AdamW]

It is indeed, that is my point: referring to a quantity simply by it's unit is not always entirely desirable. Everyone knows what you mean if you say Volts = current x resistance, but it is more correct to say p.d. instead.

It would be similar to how if you say "I am 6 foot", everyone knows you mean "I have a height of 6 feet." But if you referred to height by it's unit you would have someone asking you "How many feet are you?" which is a bit odd... I am not made of a quantitiy of feet, so the answer is 0, or possibly 2.

But I doubt anyone will be getting confused over 2-litre cars (wow, that's a small car!), and 6-footers for now... Although due to the backwardsness of the continent, they measure fuel economy in the litres of fuel required to drive 100 km... instead of just kilometres per litre. When they talk about a "3 litre car" they are in fact referring to it's high fuel efficiency that allows one to drive 100km on 3 litres of fuel. So if a German says "look at my new 3 litre Lupo!" he doesn't mean that he has performed some mad engine transplant, he means that it is efficient!

 

[ban-all-sheds]

It is indeed, that is my point: referring to a quantity simply by it's unit is not always entirely desirable. Everyone knows what you mean if you say Volts = current x resistance, but it is more correct to say p.d. instead.

And even more correct to say current x impedance, surely?

 

[AdamW]

Touché, sir

 

[vxxbcks]

I think we're all splitting hairs a bit hear!!!

Anyway as stated voltage drop increases with load, hence why overhead power cables are many 000's of volts - this reduces the current and hence the loss in the cable.

To reduce loss either use a bigger cable or increase the voltage.

 

[ban-all-sheds]

To reduce loss either use a bigger cable or increase the voltage.

How are you going to increase the voltage? You'd be much better off reducing the current...

 

[plugwash]

well increaing the voltage the voltage will reduce current

put a 1:4 step up at the start and th 4:1 step down at the end

1/16 the volt drop (ignoreing transformer ineffciancys)

NOTE: while this is a valid method it si not somehting i would advise in domestic installation

 

[AdamW]

Why just 4:1? Dammit when I have a shed at the end of a 200m cable I will be sticking the voltage (hehe) up to a good 10,000V... can SWA insulation handle that?

 

[plugwash]

i'm pretty sure you can buy swa that can

normal swa seems to be marked 600/1000 V

i think 600 is the max voltage reative to earth and 1000 is the max voltage relative to any other core

so if you used a centre tapped feed transformer you would be ok with a 1:4 step up

 

[ban-all-sheds]

And the price of a 15kW (minimum) transformer is.........?

 

[securespark]

I don't know, but it would make a mean lighting set-up in the lounge...

 

[plugwash]

its probablly not an economical setup over domestic distances

but it does significantly reduce volt drop

the opposite is also true volt drop in elv cuircuits is hell

 

[kendor]

I don't know, but it would make a mean lighting set-up in the lounge...

It brings a whole new meaning to glow in the dark

 

[AdamW]

Well, it would give you a nice hum to listen to when you are trying to sleep...