Wich one gets warmer ...

[poikkis]

Hi again

I´m still trying to gather some basic understanding about electric.

Lets say, you have 2 diffrent 1000W powersources (wind generator),

and you are loading them about 1000W to resistive load.

A) 12V generator  >>>  1000W = 83A

B) 48V generator  >>>  1000W = 21A

Wich generator will gets less warmer, how much less and why, please ?

I think (just guess) that the high voltage will produce less heat,

but is that also true, when you load them even more and the voltage start to drop down.

Is the highvoltage supply still producing less heat ?

I have difficulties to understand what happens to heat when

the voltage drops because of the massive loading.

I´m so lost.

Any ideas,please.

Poikkis

[Janne]

It's all about the internal resistanse of the generator. When you know that (you won't know the internal resistanse just from the power rating) you can calculate the I^2*R losses in the generator.

[Flux]

In theory there is no difference, you should be able to get the same efficiency from a machine at any voltage.

The low voltage machine may be more tricky to build but as far as the alternator is concerned the difference would be small.

When you consider the whole system then the high voltage machine will come off better. Diode drop becomes much less significant with high voltage and for a sensible cable cost the high voltage will again do much better but in terms of heating within the alternator the difference will be small.

This is true of a fair range of voltage but it does go wrong if you take extremes. Very low voltage high current alternators are difficult to build with many parallel connections and thick copper section. If you go to very high voltage again the insulation takes up a lot of space and you don't have room for enough copper.

For wind power you are close to the problems of parallel circuits and heavy section copper with 12v. The high voltage issue doesn't really start under 3kV so the high voltage limitations won't bother you.

Flux

[WineGuy]

Think of it this way,

Power is volts times amps; Higher volts less amps.

Heat is generated when current flows (I squared R losses)

The resistance is two fold, in the wires to the batteries and the internal

wiring of the generator.

The more current you push, the more heat is generated, internal and external.

12 volt inverters and equipment are cheap and easy to obtain, but less efficient

due to higher line losses.

48 volt systems have less line losses, but inverters and equipment is not

as cheap or easy to find.