wire question for multiple turbines

[(unknown)]

Hello,I have two 1 1/2  inch conduits from turbine site 75 feet from battery/inverter shed with two 6 awg thhn wires in one conduit to a exterior breaker panel at turbine pad.I changed turbine type to 750 watt 48 volt 3 wire ac,so I need to either pull another 6 awg or rectify at the outdoor breaker panel.

I was thinking about future growth in case I add a second turbine.

Should I pull third wire or rectify?

How do you add a second turbine using the same  48 volt feed to battery string?

Thank you for any help

[wpowokal]

You will need to send the current through as DC that is rectified at the turbine, two "wild" that is un-synchronized AC feeds can not just be put together as they will be at different frequencies and therefore not in phase.

Cable sizes and current carrying capacity will depend on your expansion plans, that you have two conduits is very helpful.

allan

[fabricator]

It seems like the better way to do it is to transport the power any distance as AC, then rectify at your control area.

[hayfarmer]

so I should put in a rectifier bridge at base of turbine and send it to battery string as d.c. and a future turbine putting out d.c. can be bridged on top of it as long as ohm's law is observed for d.c. amps?

[hayfarmer]

I guess the best bet would rectify at the turbine to d.c. the 6 gauge will make it 75 feet 15 amps with in dc loss and pull in 2 more 6 ga thhn for the next one.I was hoping their was a magic bullet ,to make two  wild ac turbine's share conductors.thank you for the help.

[TomW]

fabricator;

It seems like the better way to do it is to transport the power any distance as AC, then rectify at your control area.

3 phase AC takes 3 conductors. DC takes 2. Plus you cannot combine the AC from turbines on a common cable run. You can combine DC sources on the same cable run.

There are some specifics but that is the nutshell version.

Tom

[hayfarmer]

thanks tom,I understand the 3 conductor wild ac just was not sure that you can't bridge wild ac.still have the 40% fill  conduit space for a second pair of 6 ga for the next turbine and a spare .when I do add a second turbine I should put a diode on pos line at base of turbine on the rectified side for each turbine?

[fabricator]

Tom, when you say combine do you mean the three phases all have to run in separate conduits? My thought was he could pull another wire and have three wild ac wires in one conduit then rectify at the control room.

[TomW]

fabricator;

separate conductors Otherwise one turbine would look like a more or less short to the other. The rectifier block this from happening with the DC. As long as you observe polarity DC sources [rectified turbine outputs] can share the same cables. The cable needs to be heavy enough to handle the combined current with an acceptable voltage drop, of course.

This is where higher voltage shines. Less current for a given power so less loss in the cables.

Hope that helps.

Tom

[fabricator]

Ok, ok, ok, I was thinking in terms of one machine, I got it now, the three phase from multiple machines could not be combined but the DC can, I see it now.

[TomW]

Great!

I love seeing that flash when the light comes on for someone.

Glad we could help you find the switch!

Tom

[ghurd]

No need for another diode after the bridge rectifier before being combined in the box.

The bridge rectifier takes care of it.

G-