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3 phase bridge do-over
By clflyguy, Section Mechanical Posted on Tue Apr 24th, 2007 at 01:40:51 AM MST
Thanks Nando-DanB & Ghurd

You know, I really would be up the stinky creek in the proverbial chicken wire
canoe without the help I receive from this board. Due to you guys input I re-built
my rectifier this past weekend with sufficient heat dissipation area this time.
I calculate 108 sq. in. per diode using one of the heat sinks split in half that
our hosts have for sale. Electrical anti-oxidant cream was used between all
electrical connections due to so many different types metal involved- brass,
aluminum, copper and also under the diodes to help transfer the heat. (Also learned
here) Many thanks- here are a couple pics of the new one.

3 phase bridge do-over | 23 comments (23 topical, 0 editorial)

Re: 3 phase bridge do-over (3.00 / 0) (#1)
by harrie on Mon Apr 23rd, 2007 at 08:04:39 PM MST
(User Info)

I like it!! very neat job, and should do the job. Thanks for sharing.

Re: 3 phase bridge do-over (3.00 / 0) (#2)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Mon Apr 23rd, 2007 at 08:25:26 PM MST
(User Info)

Good Job, Where did you get the heat sinks from ?.

Do you have the specifications ?.

I am interested

Nando

Re: 3 phase bridge do-over (3.00 / 0) (#3)
by clflyguy (sidney.raiford@gmail.com) on Mon Apr 23rd, 2007 at 08:52:57 PM MST
(User Info)

Thanks Nando,
I got the heat sink here, at Otherpowers store. Before I cut it in half it was
6"x8" with 40 fins @ 1.25" deep making 648 square inches of area.

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#4)
by willib (willibur at comcast dot net) on Mon Apr 23rd, 2007 at 09:10:06 PM MST
(User Info) http://www.njwind.com/webcam.html#

pretty cool , but just make sure your three phase connections dont short to the heatsink
Carpe Ventum (seize the wind)

Re: 3 phase bridge do-over (3.00 / 0) (#5)
by clflyguy (sidney.raiford@gmail.com) on Mon Apr 23rd, 2007 at 09:21:32 PM MST
(User Info)

Hey Willib-
Elucidate please...

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#6)
by willib (willibur at comcast dot net) on Mon Apr 23rd, 2007 at 09:25:13 PM MST
(User Info) http://www.njwind.com/webcam.html#

well the three phase connections look hinged ?
it may be better to make the connections in the middle
Carpe Ventum (seize the wind)
[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#7)
by willib (willibur at comcast dot net) on Mon Apr 23rd, 2007 at 09:35:11 PM MST
(User Info) http://www.njwind.com/webcam.html#

just make sure that they dont pivot twards the heat sink , thats all ,
it will probably be fine
what size wire are ya gonna use from the windmill?
Carpe Ventum (seize the wind)
[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#8)
by clflyguy (sidney.raiford@gmail.com) on Tue Apr 24th, 2007 at 05:55:47 AM MST
(User Info)

Hey Willib,
Yeah, the assembly is locked front and back so no hinging can take place. The
wire looks like it will be ok at #3AWG for a 230' run. In the range of amps & volts
that I am anticipating my line losses look to run between 7% and 11%. I know the
cure for that is to throw more money at it (copper) but geez, 690' of #3 is gonna sting! And I still have to get guys!

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#9)
by willib (willibur at comcast dot net) on Tue Apr 24th, 2007 at 09:13:52 AM MST
(User Info) http://www.njwind.com/webcam.html#

thats pretty thick wire
it may hurt more than a little sting :)
Carpe Ventum (seize the wind)
[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#10)
by clflyguy (sidney.raiford@gmail.com) on Tue Apr 24th, 2007 at 11:22:25 AM MST
(User Info)

True enough,
But even using #3gage I'm losing 7.77% to voltage drop at 40 amps- I want SOME of the little electron thingies to make it all the way to the battery bank!

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#11)
by willib (willibur at comcast dot net) on Tue Apr 24th, 2007 at 11:48:09 AM MST
(User Info) http://www.njwind.com/webcam.html#

is you #3 going to be able to make the bend ?
also what is to prevent the whole thing from twisting
the two wood spacers have only one screw in each end
Carpe Ventum (seize the wind)
[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#12)
by clflyguy (sidney.raiford@gmail.com) on Tue Apr 24th, 2007 at 12:20:34 PM MST
(User Info)

Well,
The wires are secured and hung on a curved "tongue" at the top of the turbine. The
power doesn't get rectified till it's inside the battery building, so those #3's
are going to be anchored, bent and directed as needed on the plywood panel that the
rectifier, inverters, controllers & whatnot are all mounted on. By the time the ends
are ready to be clamped into the connectors there won't be any weight or twist on
them at all. I am however thinking about running them through a short piece of
hose at the tower base before they dissapear into the UG conduit to take care of any possible chafing associated with raising and lowering the tower. -Gus

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#14)
by coldspot on Tue Apr 24th, 2007 at 05:16:05 PM MST
(User Info)

Great work done there !!!!!
Your very skilled !
:)
But,
I'll be calling my "tower support cable lines"
just that!
Because
After reading
"have to get guys!"
I'll be thinking a bit before I speak, (I hope)
My friends that are still not on the R.E.
would have way to much fun with that!
LOL
:)
"the plywood panel that the
rectifier, inverters, controllers & whatnot are all mounted on"
I hope this isn't getting battery fumes and is in different area of battery building
$0.02

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#15)
by clflyguy (sidney.raiford@gmail.com) on Tue Apr 24th, 2007 at 07:59:55 PM MST
(User Info)

Hey Coldspot,
I went back and re-read that- OMG! Me, the king of the double entendre actually
wrote that without the slightest thought of the OTHER way that could be taken...
I'm gettin' old, man... Slippin' bad...
And yes, the battery bank has a room of its own, KOH & H2SO4 mists can both wreak
havoc on electrical goodies, there is also a 24v brushless muffin fan mounted in the
ceiling at the highest point to pull negative pressure on the room.

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#13)
by veewee77 on Tue Apr 24th, 2007 at 04:19:03 PM MST
(User Info)

One thing I would do different, especially if these get pretty hot, would be to make the connections between the rectifiers with the copper formed in a slight "s" shape or like ~ <(enlarge the tilde) Because due to expansion and contraction, those straight ones are likely to break in time. a slight "s" shape will allow the metal to expand and contract with room to "flex".

Looks GREAT, though!

Doug

Re: 3 phase bridge do-over (3.00 / 0) (#18)
by clflyguy (sidney.raiford@gmail.com) on Wed Apr 25th, 2007 at 08:57:24 AM MST
(User Info)

Hey Doug,
THAT is an excellent idea, consider it stolen. New S-shaped copper blades
will be installed sometime this week. Thank you- Gus

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#16)
by Ungrounded Lightning Rod on Tue Apr 24th, 2007 at 11:41:32 PM MST
(User Info)

You should not be using wood for the spacers. Fire risk - both from heat and from eventual creation of a carbon track between the + and - heat sinks.

Re: 3 phase bridge do-over (3.00 / 0) (#17)
by clflyguy (sidney.raiford@gmail.com) on Wed Apr 25th, 2007 at 07:49:25 AM MST
(User Info)

ULR-
OK, makes sense,
The other choices are laminated fiberglass sheet and plastic cutting board
material.. Either/or? Also, in the photos the angle of the shots prevent you
from seeing the 1/4" thick fiberglass spacers between the wood and the heat
sinks. Do you think the wood is conductive enough to present the possibility of
eventually forming a carbon track between the attachment screws? -Gus

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#19)
by Ungrounded Lightning Rod on Wed Apr 25th, 2007 at 06:09:35 PM MST
(User Info)

The other choices are laminated fiberglass sheet and plastic cutting board
material.. Either/or?

I'd go with fiberglass, ala PC board material. Stable and good for reasonable temperatures. With a plastic cutting board you have the risk of melting.

Also, in the photos the angle of the shots prevent you
from seeing the 1/4" thick fiberglass spacers between the wood and the heat
sinks.

But you seem to have conductive screws into the wood.

Do you think the wood is conductive enough to present the possibility of
eventually forming a carbon track between the attachment screws?

I'd expect that, yes. Especially for higher voltages and/or if the wood is in an environment where it can absorb moisture.

Wood is basically polymerized sugar. The more it's heated and/or has a current driven through it, the more the long-chains release water and become more graphite-like. It's a positive feedback system that ends with a narrow carbon track and a lot of heat. That's one reason you always want an insulator between any significant voltage and wood, and to ground the wood side of things if the wire carrys AC (which can capacitively couple through the insulator and drive a current despite it).

(Or at least that's how I understand it - having never violated the rule personally and started a fire...)

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#20)
by dpshort218 on Fri Apr 27th, 2007 at 12:41:45 AM MST
(User Info)

I agree with one comment about not using the wood since it can be a fire hazard and carbon build-up path. You can also help yourself out with a cheap roll of electrical tape over the bus bars, lugs and all exposed conductors. Use heat shrink on bars for a slightly prettier look.
David

Re: 3 phase bridge do-over (3.00 / 0) (#21)
by laskey on Sat Apr 28th, 2007 at 06:18:01 PM MST
(User Info)

Ummm... I don't think I'd use heat shrink or electrical tape on it, if this thing is supposed to get as hot you're talking about, it'll end up just stinking of burning plastic and glue.
I would use aluminum bars instead of wood, with mica washers on both sides as insulators, and I'd add heat sink paste on all the bolts where the diodes touch the heat sink to increase thermal conductivity, and if you're worried about electrocution hazards, put the thing in a well ventilated plexiglass box. That way you can show off what a good job you did... Because it looks great. :>

Cya,
Chris

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#23)
by thyristor on Sun Apr 29th, 2007 at 03:35:10 PM MST
(User Info)

A material called "TUFFNOL" is the perfect choice for the insulating spacers. It's an industrial material similar to "BAKELITE" and has extremely good mechanical strength and is a very good insulator and can withstand a great deal of heat.
Good luck!
Thyristor

[ Parent ]

Re: 3 phase bridge do-over (3.00 / 0) (#22)
by Kevin L on Sun Apr 29th, 2007 at 12:08:05 AM MST
(User Info)

At first I didn't think wood charing would be an issue because wood combustion temperature are rather high, but after looking at the following document Aluminum is probably a better choice. http://www.fpl.fs.fed.us/documnts/fplmisc/rpt1464.pdf

Also is there a specific reason you are rectifying the current before the 230 ft run. Seems like you could run three phase AC on much cheaper wire.

3 phase bridge do-over | 23 comments (23 topical, 0 editorial)

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