Bridge rectifier location?

[NukeManSoon]

I always thought that ac had less line loss then dc over longer distances? But I see a lot of bridge rectifiers on the gennies, which is the best setup?

[K3CZ]

DC vs AC:   It makes no difference, all other things being equal.  If you rectify at the alternator, then all the juice must go down one pair of heavy wires to the load as DC.  If you have a multi-phase generator, then the energy will be distributed among several wires on its way to the remote rectifier, if you choose to carry the phases all the way to the the rectifiers with lighter gauge multi-conductor wire. If the amount of copper is the same, the results will be the same.   Your call!

[scottsAI]

DC has less line losses over great distances.

DC is only used for great distances because, it requires conversion from AC to DC back to AC. Conversion cost $ and has power losses.

With hundreds of miles of line the AC frequency has dv/dt (or capacitances) losses along with the line losses.

AC is much easier to correct for line voltage losses. Multi tap transformers.

When the above statements are considered we are talking hundreds of miles.

AC power transmission is used more often. AC is the way we use the power.

Now back to your question:

The remote distances most gennies are, the AC/DC is not the real issue.

People make the gennies output the voltage their system needs.

Rectification at the gennies allows two wire for the DC.

AC is (most designs I see here) 3 phase. Would require three wires... There are some single phase, which would then use two wires.

If your sending your power long distances, there are line losses I*I*R, when they are above 3-5% the wire size must be made greater or the voltage stepped up to reduce the current. Much easier to step up AC than DC.

The power math for 3 phase AC, the third wire allows you to carry about 57% (or is it 60%) more power. The wire can be thinner even with the three wires than the two wires carrying the same DC power (or single phase AC). Therefore 3 wires cost less. Copper cost.

You will note most high voltage Power lines are in threes. When only two lines, then they are most likely DC. You might be wondering why use DC? The voltage is very high 350KV, this easily makes up for the differences.

My personal choice would not put the rectifier in the gennies, one less thing to go wrong up there.

Have fun.

[nothing to lose]

"You will note most high voltage Power lines are in threes. When only two lines, then they are most likely DC. You might be wondering why use DC? The voltage is very high 350KV, this easily makes up for the differences.

My personal choice would not put the rectifier in the gennies, one less thing to go wrong up there."

I understood most of that

But now I have only 2 wires from the power lines at the road to my meter. Also I beleave the lines running down the road are only 2 lines to power the transformer that feeds my lines. Surely my house is not being fed DC?

 Then again this crappy power I get could be about anything, certainly it's not always 120V

Are these the type l;ines you reffer to, or you talking about the realy big ones feeding these?

I agree about the rectifier not being at the gennie, if it fries you have no way to shut down the gennie, if the rectifier is at the batteries and fries you can still short the AC lines comming from the gennie to stop it. Like high winds storms etc..

Without a load it freewheels.

Course if like mine now it would not matter. Trees blooming out, nice breeze (fair wind) I have no load on the gennie at all, and I look up to see my mill dead! Surrounded by fluffy trees on 3 sides

Was not like that last week! Time to move it or cut somethings!!

[scottsAI]

Your house is AC! You know that.

You have single phase AC, but most homes actually do have three wires coming to their home. Two for the 220 and a neutral. But it's single phase.

Yes, I was talking about the high tension lines.

Sounds like you have a good grasp of the situation.

Now you only need a taller tower or cut down some trees.

Choices! If you cut the trees then you have fire wood to heat with:-)

Have fun.

[nothing to lose]

Yes I know the house is AC, though as bad and unreliable as the power is at times I wonder if they know that!

I think I have 2 110ac lines in the air feeding the meter. The third line is grounded at the pole, no overhead line 3.

"Now you only need a taller tower or cut down some trees.

Choices! If you cut the trees then you have fire wood to heat with:-) "

Yes but if I cut the trees I lose the shade, more heat means more cooling, use more power.  

Have to move the mill, not a good place for taller tower.

 Fire wood is about free anyway, depending where I get it.

HUH, so goes life. I will love Canada this summer

Let wife worry about moving the mill, :>

Just joking.

[ivandenisovich]

There are a couple of other reasons to mount your rectifier near your batteries;  a rectifier or diode is a semi-conductor, and therefore can be damaged by spikes from lightening or static discharge.  If is it on the ground, very easy to replace.  Up on the tower next the the generator, makes things more difficult.  Also, if you are interested in doing any switching of three phase from star (AKA wye) to delta for low speed/high speed operation, it would be better to mount all of the controls where you can get to them, for the same reason as above.  As far as losses are concerned, the E=IR is the same for low frequency AC as it is for DC.

Paul