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Power Rectifier Diodes
By harrie, Section Wind Posted on Sat Oct 21, 2006 at 12:09:25 AM MST
Can these be used?

I purchased a lot of 5 IN4045 diodes 275 amp 100 volt. Not having that much knowage of electronic equip, I was surprised to see how big they were. The reason I wanted them, was because I have had nothing but trouble with the 35 amp bridge Rectifiers. On my 12 volt system, I have a total of 9 rectifiers on a large heat sink, but due to times the genny puts out over 100 amps, I keep burning them out. My question is , will I beable to use the stud diodes, and how they need to be installed. Im thinking I should have maybe ordered a 800 volt, 150 amp three phase module diode? Thanks in advance
Harrie

Power Rectifier Diodes | 11 comments (11 topical)

Re: Power Rectifier Diodes (3.00 / 0) (#1)
by mitcamp on Fri Oct 20, 2006 at 09:45:58 PM MST

harrie, looks like we purchased the same diodes from the same seller, 5 in a blister pack. I was having the same problem with rectifiers. When I got my diodes unpacked and seen the size I knew I was going to have a problem fitting 6 of them on top and, they were going to require a heavy duty heatsink. I searched the board for some pictures of heavy duty DIY 3 phase bridge rectifiers constructed with the large stud diodes and found 2 I could try uploading them, to my photo,s in my files if you need them.
I got back on Ebay and ordered a 3 phase bridge rectifier 800v 150 amp. I got it yesterday, and this is what I,ll be using until I can make a few modifications up on top, to make room for the stud diodes.

I also ordered 6 of these Diode Doublers 400v 100 amps. You can tie 3 of these together for 3 phase. I ordered these just for insurance.

This may be overkill but my tower is 100 ft high and I don,t want to be up on it any more than necessary this winter.
Two or 3 weeks ago I put 3 new 50 amp single phase bridges up on the tower and they are still hanging in there. My machine is similar to yours,except I changed mine from 12v to 24v and the my amps dropped in half. I see a lot of 40 to 60 amps now, it used to be over 100 amps at 12 volt. mitcamp

Re: Power Rectifier Diodes (3.00 / 0) (#5)
by harrie on Sat Oct 21, 2006 at 08:43:57 AM MST

Yes, that is the module I was thinking I should have ordered, and I can understand why you wouldnt want to install those big stud IN4045s up on the tower. Flux seems to think they will work Ok, so I think I will try them. As Flux said also, is that I will need 6 of them. If I understand him correctly, you really need 3 stud anode, and 3 stud cathode. The group of 5 that I have, I beleive are all cathode, but can be used that way with more of a messy heat sink application? Let me know how the 3 phase module works out. Maybe tho, you will never find out if the 50 amp bridges work out. Its fun to climb the towers. ha. keeps you in shape, and the view is nice too. Ha . Thanks for the repley.

[ Parent ]

Re: Power Rectifier Diodes (3.00 / 0) (#2)
by Flux on Sat Oct 21, 2006 at 02:42:23 AM MST

You need 6 of those not 5.

They will be excellent but a bit messy to mount, it is easier to have 3 stud cathode and 3 stud anode. You can then screw 3 to each heat sink, the heat sinks form the dc connections and you join the tails to form the ac connections.

You will need to mount 3 one one heatsink and the other 3 on individual sinks.

You will not need the monstrous heat sinks required for the 35A bridges.

They are a better choice than the 3 phase potted bridges that have all the nasty properties of all these isolated base constructions.
Flux

Re: Power Rectifier Diodes (3.00 / 0) (#3)
by mitcamp on Sat Oct 21, 2006 at 08:08:06 AM MST

Hi Flux, You told me about 3 cathode to case and 3 anode to case a few weeks ago. I had 6 of the 1N4593R anode to case in my parts bin and was watching for a set of diodes of the opposite polarity. I just got the 1N4045 cathode to case the other day. I have been waiting for you to reply so I could ask you about mixing the DO8 and the DO9 configuration together. I assume its o.k to mix them.
My next question could help both of us at the same time and many others also. harrie and I have similar machines his 12v and mine 24 v What do you suggest for heatsinks and size for mounting 3 diodes to each. Aluminum angle 2in x 2in x 1/4 in thick and 12 inches long so we are talking about the same thing. Would this be enough or do we need more area.
Electrondady used aluminum channel, looks like 8 in long and 4 in wide and 1/4 in thick, doubled back to back. I dont want to over build, because I am short of space with mine going up on top at the generator.
I,ve got enough information from you so far that I,m soon going to have to send you a checque. Thanks Mitcamp

[ Parent ]

Re: Power Rectifier Diodes (3.00 / 0) (#4)
by Flux on Sat Oct 21, 2006 at 08:42:24 AM MST

Yes you can mix the 2 types. It is very difficult to give an idea of the heatsink size, there are too many unknowns.

Your 24 v case should not be too demanding, but I really have no idea of the air flow round your bridge. The other totally unknown factor is what the average current is for how long. Normally if you have 50A with wind power it will not be continuous, if it is then heatsinking becomes more critical.

For short term peaks with cooling intervals, channel or angle will be fine.

If the load is sustained then large finned surfaces are far more effective at removing the heat. Commercial finned heatsink intended for natural air cooling is very expensive unless you get a bargain. Much of the commercial stuff produced now is intended for fan cooling.

I have had good results with fins made of concentric u shaped pieces of aluminium sheet. 3 sheets of 1/8" will give a substantial root area to conduct from the diodes and the fins will remove heat by convection.

If the outer piece is about 6" high, 4" wide on the flat where the diodes are and with fins bent at the ends about 4 " long, that should manage anything you can throw at it. If you have some forced draught then this may be well over the top.

Heat sink compound between layers and under diodes will help a great deal.

I have something smaller than this on a 1.5kW 24 v machine in a reasonably enclosed box at ground level, using pressfit diodes and that has been no trouble, but we never get long periods of constant output as may be the case with a machine on a very tall tower in clean wind.

I think much of the failure of the 35A bridges is from current sharing, heat from the crappy connections and failure to transfer heat to the heat sinks. With decent diodes I think most of the trouble will vanish. Try not to let the part of the heat sink near the diode base exceed 60 deg C, but most likely you will be within diode limits at over 80C.

Harrie may need to be a bit more careful with 100A but again I think things will be far easier than with the 35A bridges.

Another factor with those bridges is that there are crap devices available, genuine IR or General semiconductor units don't cause much trouble, it's the unknown ones that fail.
Flux

[ Parent ]

Re: Power Rectifier Diodes (3.00 / 0) (#6)
by harrie on Sat Oct 21, 2006 at 08:48:54 AM MST

Yes Flux, that could be part of my trouble with the 35's , I guess I have always said you get what you pay for, but still wind up trying to save money and by junk. Thanks for the information, Harrie

[ Parent ]

Re: Power Rectifier Diodes (3.00 / 0) (#7)
by tecker on Sat Oct 21, 2006 at 09:23:01 AM MST

I got some bussbars connected to p1 heatsinks arranged so the the phase bars face the
dc out The studs on those monsters are big that's a factor I looked at the cut sheet I think it say 3/4 16. That means you want a through hole ( big tap)

Re: Power Rectifier Diodes (3.00 / 0) (#8)
by stephent on Sat Oct 21, 2006 at 09:38:04 AM MST

Anyone suggested isolating the heatsinks from metal/conductive paths (excepting the battery connections) when using discrete stud mount diodes?
Yet?
Or at least one of them?

Re: Power Rectifier Diodes (3.00 / 0) (#9)
by Carl B on Sat Oct 21, 2006 at 02:12:07 PM MST

this is a bridge rectifier I Built a few years ago, to use
with my AC welder. To use the stud mount Diodes required the
use of three heat sinks, (actually one cut into three pieces)

[ Parent ]

Re: Power Rectifier Diodes (3.00 / 0) (#10)
by harrie on Sat Oct 21, 2006 at 03:28:05 PM MST

Hi carl, thanks for the picture, yours of course is single phase AC, so the three phase would require more stud rectifiers, but at least it gives one an idea how to do it. You are changing your AC welder to DC, Correct? My welder is a AC Lincoln, and I have always wanted DC.

[ Parent ]

Re: Power Rectifier Diodes (3.00 / 0) (#11)
by Carl B on Sat Oct 21, 2006 at 05:43:59 PM MST

Hi! Harrie,
I had some critical welding to do and just threw this together from
parts I had on hand. It is pulsed DC, but it works a lot better than AC,
since the current is going in one direction, also some capacitors
to smooth out the pulses, would help a lot.
I didn't convert the welder to dc, I just clamped the leads from the
welder to one side of the bridge, and some jumper cables to the other
Side.
I don't use it a lot anymore, if did i would convert it, I may anyway
btw it is a lincoln 220
Carl

[ Parent ]

Power Rectifier Diodes | 11 comments (11 topical)

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