Author Topic: Monday May 1 (Read 9003 times)

DanB · « **on:** May 02, 2006, 05:21:56 AM »

Another fun Monday. We didn't have a lot we needed to do - so we decided to build a rectifer for Rich's 7' machine. Pictured above are most of the components we started with. We have a bunch of heat sinks - so we used one of those. The terminal blocks are oversized but should work well - I got a bargain on those on ebay. It's only a 7' machine and not capable of much more than 300 watts so 3 35 amp bridge rectifers should do fine even at 12V.

Pictured above Rich cuts up some Aluminum plate to mount to the heat sink to help mount it to the wall - and to give space for an ammeter and a kill switch.

An orbital sander leaves a nice looking finish on the Aluminum plate.

We bent the plate (we dont have a brake so we used the vice - some angle iron and a hammer) and sanded it - this serves to help mount the heat sink to the wall and give space for the ammeter and the heat sink.

Rich is drilling out 5/32" holes to mount rectifiers and terminal blocks.

Pictured above he's tapping the holes 10 - 24tpi.

It's important when mounting bridge rectifers to use some 'silicone heat sink compound'. It's a paste that never seems to dry - but it helps transfer the heat from the rectifier to the heat sink. You smear a little on the rectifer... then bolt it down to the heat sink.

There we have all the parts screwed down to the heat sink with 10 -24 tpi screws.

Each of the 3 leads from the 3 phase AC input hook up to both AC leads of their own bridge rectifier.

For a kil switch we used an old DPST (double pole single throw) toggle switch. On one end of the switch the leads are tied togeter and hook to one 3 phase AC input. Each of the other two leads to to the other two 3 phase inputs. When the switch is off the wind turbine can run - when it's 'on' all 3 leads are 'shorted' and the wind turbine cannot run.

Pictured above it's all hooked up. All the positive and negative leads on the rectifier are in parallel. The DC - goes through the ammeter and then out to a terminal block.

So there's the basic wind turbine rectifier from the front. It contains a 3 phase rectifer, a 50 amp meter and a stop switch. All the basics...

Of course Scotty came up today with some problems... one of the rectifiers in his 11' 6" dia wind turbine blew. He needs to double his capacity there I think (6 rectifiers) - this is about the 4th time this has failed. We replaced the bad one - that may hold up till next monday if it doesn't get too windy.

For those who recall the postings about Scotts 'mini petter' diesel and the alternator we built for it...

the governor got stuck and it ran up to over 3000 rpm. We had a steel band around the magnets. Part of it tore off and magnets went flying earlier today - some hit his gate - some might be in orbit. On their way out they wiped out the meters on the generator but didnt cause any real significant damage. (no dogs were injured) Scary stuff... anyhow - he brought up the remains of the magnet rotor.

This should make all of you slip ring enthusiasts out there happy. Pictured above is the line that ran down Scotts tower. It got twisted up real bad over the last couple years and finally shorted out at a splice he'd made in the line about half way down the tower. The line had to be replaced. This isn't 'normal' - Scott's in a very turbulant place in the bottom of steep canyon. His tower is up on a steep hillside - almost 60' tall - but still.. it's not uncommon to see his wind turbine do a 360.

Poor Scott.. his diesel blew up - his wind turbine rectifiers blew - his line shorted out... and I think hes on his 4th set of blades in 2 years. Not to mention a few tower failures...

another shot of Scotties line that came out of his tower.

Scott spent some time building the new tower for his new 11' machine (the one with the wincharger blade and the airbrake) - this should be going up soon.

I also got my shipment today from shopmaniac.com (thanks to whoever posted that link 2 weeks ago). I got some vinyl ester for stators (its supposed to take very high tempurature - be stronger - and shrink less than polyester) and I got a bunch of fairly inexpensive epoxy which I plan to play with for magnet rotors. Polyester resin is proving to be frustrating for magnet rotors. Of course... there was pizza and dogs and all the other usual stuff.. didn't get pictures of that though.

jmk · « **Reply #1 on:** May 02, 2006, 07:39:29 AM »

Hi Dan, This post came at a great time for me. I am getting ready to raise my tower, and still need to run my electric run wires. I just purchased one of your large heat sinks. They look like they will work great! I was wondering were a good place to look for the heat sink compound? Would a hardware store cary that or should I go to an electric wire supply shop? I am running #6 welding wire down the tower and bought a three conecter like the three two wire conecters you used on the heat sink. I am planing on useing this conecter at the bottom for a plug so I can untwist the wires. I found a twist lock plug but it cost $60, so I opted to this conecter. Do you have any other sugestions? I am putting the turbine on a 32' test tower. It will be in alot of tubulance.

DanB · « **Reply #2 on:** May 02, 2006, 07:48:40 AM »

Hi JMK - I doubt a hardware store will have heat sink grease. Radio shack should... any electronics supplier will have that - or.. type it into google and you'll find lots of choices.

3 prong locking plugs are expensive - Id think you can do better than $60 though. We're lucky - the local habitat for humanity shop has a bushel of them @ $2 ea...

I expect your connector will work fine till you find something better.

jlt · « **Reply #3 on:** May 02, 2006, 08:21:17 AM »

hi dan i tryed that e mail address of epoxy resin but didnt work.how are you comming along on the 20 ft alt. are you going to test it on the ground,or just put it up and see what happens. my 15 inch duel roter is finaly comming together.keep up the good work.

oztules · « **Reply #4 on:** May 02, 2006, 08:24:57 AM »

And for other Yokels like me .......a bushel is: .....equal to 4 pecks

And if your unedumacated like me....a peck ( is 1/4 of a bushel)

a peck is near enough to 9 liters....which kinda makes a bushel around 36 liters.

learn something new every day, thanks Danb.

how many measurement systems do you people have?

......oztules

Tropical son · « **Reply #5 on:** May 02, 2006, 08:26:27 AM »

Hi DanB , great post again , as usual.I really enjoy your Monday postings. They are very informative , especially for us beginers.I was wondering what gauge of wire you used to make your connections. Thanks .

Kenny

DanB · « **Reply #6 on:** May 02, 2006, 09:21:20 AM »

When it comes to measuring things - I like systems where 1 unit is a 'convenient' amount...

bushel of locking plugs (a handy box full that you can barely pick up)

cup of coffee...

pint of beer

It adds color to life and we're smart enough as people to deal with multiple systems I think. the metric system seems kind of dull and boring and often inconvenient, though it is handy for some things.

QUAZ HOLT · « **Reply #7 on:** May 02, 2006, 11:35:28 AM »

double his capacity there I think (6 rectifiers) Have you tried to use ballast resistors on the bridge diodes. Unequal current distribution causes one of the diodes in the bridge to hog the power. Also this condition worsens as the diode heats up.

Put a little change back into you pocket. Bill,

JYL · « **Reply #8 on:** May 02, 2006, 06:29:28 PM »

Anyone store that sales computers motherboard and processor will have the equivalent heat sink grease.

harrie · « **Reply #9 on:** May 02, 2006, 10:48:47 PM »

Hi Dan. neat looking set up. I have been having alot of problems with rectifiers lately, I have 9 full wave hooked to a large heat sink, using paste,comming from my 12 foot dia. duel rotor in the 9 coils, 12 mag. each rotor turbine, and keep blowing the rectifiers. I have been getting them from allelectronics, at a price of 22.50 for ten 35 amp. They are 200 P.I.V. Are they no good? I was thinking that maybe all the #10 wires from AC should be the same length so that equal voltage follows each wire, or wont that make any difference. Thanks for any help. The turbine will at times do over 100 amps at 12 volts.

Flux · « **Reply #10 on:** May 03, 2006, 08:57:46 AM »

Harrie

Yes it will help if you keep equal length wires on the ac sides and ideally do the same thing on the dc side.

Quaz Holt in a post above mentions this with sharing resistors, your bits of wire will do the same thing if they are long enough to have a bit of resistance.

There are bridges and bridges and some I suspect are pretty ropey, depends where they come from.

I find that these bridges can not normally take their 35A rating into battery loads( more like capacitor rating). When you parallel there is a significant de rating on top of that.

I have not bothered with those bridges except for lower currents, it is a bit more expensive to use proper diodes and build your own bridge but the decent packages do seem much more reliable.

Even the press fit automotive type diodes are far more effective but unless you have a hole punch to mount them they are awkward, the hole needs to be fairly accurate to get a good fit without damage.

I find that better diodes need much less heat sinks. The other thing to watch with bridges is to spread them out on the heat sink otherwise they all sit on a hot spot.

Flux

harrie · « **Reply #11 on:** May 03, 2006, 09:07:32 AM »

Thanks Flux, I dont know what we would do without your help!

QUAZ HOLT · « **Reply #12 on:** May 03, 2006, 12:37:04 PM »

"wire will do the same thing if they are long enough to have a bit of resistance."Yes copper has some resistance, but here is a simple way that will allow you to balance the current with nichrome wire. Nichrome can be found in the drier that you never use. Nichrome's resistance is 4 inches long and .02 square inches is = to approx. 2 ohms. This is the way I do it.

Just cut a small piece and crimp a terminal to one end. I found some 1/16 inch nichrome, this is what I use. The bridges are inexpensive and the resistor wire is plentiful. I heard a rumor, Danb has some bridges to sell

Bill.

harrie · « **Reply #13 on:** May 03, 2006, 05:30:15 PM »

Hi bill. Thanks for the suggestion, when I find a dryer i might just try it. Oh and I kind of expected to get a little static about where I bought the Rectifiers. I do buy all the mags from dan, so that should be good for something. Ha.

Great Fun, harrie

powerbuoy · « **Reply #14 on:** May 03, 2006, 05:41:02 PM »

:-)))) that was my posting two weeks earlier ... glad it helped someone out

Powerbuoy

powerbuoy · « **Reply #15 on:** May 03, 2006, 06:41:19 PM »

resin link --->>> http://www.shopmaninc.com/fillers.html

DanB · « **Reply #16 on:** May 03, 2006, 09:23:48 PM »

One of the values of a discussion forum! Thanks powerbouy...

Moosie · « **Reply #17 on:** May 04, 2006, 07:58:19 AM »

I love these posts, so clear, and easy to understand. One thing I noticed:

Is one of the legs on the middle bridge rectifier not being used?

What would the effect be, if you didn't have the ammeter, and connected that in series just like the negative side?

I apologize for my ignorance......

asheets · « **Reply #18 on:** May 04, 2006, 09:46:46 AM »

Give these folks a call -- http://search.ebay.com/_W0QQfgtpZ1QQfrppZ25QQsassZwestfloridacomponents -- Their prices are good, and they deliver fast. I've been grabbing 600VAC/50A full phase bridges from them for about $1 apiece (all out at the moment, as I bought out their inventory recently, but they'll be getting more soon). Friendly folks, too...

SparWeb · « **Reply #19 on:** May 04, 2006, 12:36:31 PM »

From Flux:

"I find that these bridges can not normally take their 35A rating into battery loads( more like capacitor rating). When you parallel there is a significant de rating on top of that."

Before relying on any rectifier, it's worth looking at the spec sheet from the manufacturer. If the mfr doesn't have a spec sheet, that should tell you something. Of the specs I've seen for bridges so far, none allow full current under real-world conditions. Maybe if you immersed the block in liquid nitrogen....

If Harrie can get 100 amps from his 3-phase alt, then no kidding he's going to blow up his 35Amp bridges.

harrie · « **Reply #20 on:** May 04, 2006, 07:03:26 PM »

I think 9 X 35 equal 315 steve, or am I missing something?

Spelljammer · « **Reply #21 on:** May 09, 2006, 03:23:29 PM »

what about using an old car alternator rectifier block from the scrap yard? About 100 amp should do. I've heard that they over-rate a lot of those. Like 60 amp alternator may have 100 amp diodes in there and PIV maybe at 100 - 200 volts.

I don't like paralleling diodes because one will always get more current...too hard to balance. Internal resistance changes under load and heat...so it makes it even harder. When one finally fails, then the other will fail right after.

Anyone have any specs on typical diodes in a 60 amp car alternator?

DanB · « **Reply #22 on:** May 09, 2006, 10:02:31 PM »

theyd work well I think if you figure out how to add to the heat sink. To run at capacity they need lots of air going by - theyll burn up at a fraction of their rating without it in my experience.

SparWeb · « **Reply #23 on:** May 10, 2006, 01:09:56 PM »

Harrie,

I don't know exactly how you've hooked the rectifiers up, but if you're counting 9, then either you're using 3 in parallel per phase, or you're rectifying each phase independently.

In the 3 parallel rectifiers scenario, you should expect one to be taking more current than the other two. The forward voltage drop is probably not the same from one bridge to another.

This datasheet from IR details the specs for your class of rectifiers. For 35Amp rectifers, go to page 5 and you'll see the steep drop in allowable case temperature for the current. Other limitations apply - the power loss chart will tell you how much heat the sink must dissipate, for example. I consider this a complete and detailed datasheet for a bridge rectifier. Their competitors' datasheets don't state these limitations. IMHO, that puts IR above NTE.

One last point: you said you got them cheap. Then you definitely can't expect performance this good!

domeguy · « **Reply #24 on:** June 14, 2006, 02:21:42 PM »

Hey Dan, those terminal blocks look great. What are they called? I can't seem to find them anywhere.

-Lee

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Author Topic: Monday May 1 (Read 9003 times)