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10' Turbine Rectifier Parts Questions


By arwenvaughan, Section Wind
Posted on Mon Jun 29, 2009 at 12:20:29 AM MST
10' Turbine Rectifier Parts Questions

Quick question. What is the best full-wave bridge rectifier to use with the 48 volt stator on the 10 foot other power wind turbine. I want to order them but there seems to be many different models. How the hell does "35 A 200 PIV BRIDGE RECTIFIER" differ from "35 AMP 600 PIV BRIDGE RECTIFIER"? Is this a voltage difference? If so, what voltage rating would work best with the 10 footer with the older style alternator using 2x1x0.5 magnets?

I was going to order them from this website recommended in the Homebrew Wind Power book...

http://www.allelectronics.com/make-a-store/item/FWB-252/25-A-200-PIV-BRIDGE-RECTIFIER-/1.html (Is this the right one?)

Also, what would you recommend for Terminal Blocks and the DPST switch? I want to just order these from the web. I have found a few items on the net but have any idea what is best and I don't have the time to find salvaged parts right now. Any ideas?
10' Turbine Rectifier Parts Questions | 11 comments (11 topical)

Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#1)
by arwenvaughan on Sun Jun 28, 2009 at 07:54:10 PM MST

I mean is this the right one...?

http://www.allelectronics.com/make-a-store/item/FWB-354/35-A-400-PIV-BRIDGE-RECTIFIER-/1.html



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#2)
by imsmooth on Sun Jun 28, 2009 at 08:08:59 PM MST

The 35A is the maximum amperage the rectifier should see.  I believe this is total amps by summing all phases.  The 200 or the 600 refers to the maximum phase to phase voltage.

You should pick the rectifier based on what you expect, adding a safety factor.  If you expect no more than 10A out, then a 20A rating would be good.  If you expect no more than 300v then 600v would work well.

The voltage expected is based on the turns you have per coil and the magnet strength.  I would construct test coils and test them with your magnets in order to determine what rectifier you need.  Since these rectifiers are not that expensive it is not unreasonable to oversize.
Jonathan



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#4)
by arwenvaughan on Sun Jun 28, 2009 at 09:16:06 PM MST

Thanks for the comments. I guess it would be helpful then to know what the voltage is for the 10 footer then at a full furl. Does anyone know what the DC voltage is on this machine at "maximum" rpm. Since I am building this 10 footer straight out of the Homebrew Wind Power book with no modifications I would imagine that someone out there who has built one can help me out on this question.

[ Parent ]


Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#5)
by DanB on Sun Jun 28, 2009 at 09:24:20 PM MST

so long as it stays on the batteries the voltage should never really get too much over 60, but  - if the battery becomes disconnected then I suppose it could get up towards 250-300V (this should really never happen though).

[ Parent ]


Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#7)
by rossw on Sun Jun 28, 2009 at 11:21:59 PM MST

I just want to clarify here... while the above info is not actually WRONG, it implies some things that are. The missing key word is "minimum".

Eg, "If you expect no more than 10A out, then a 20A rating would be good." is not actually WRONG but should probably say "then a 20A rating should be your MINIMUM."

If the diode pack you are looking at is 35A, then its fine (very likely a better choice in fact) than trying to hunt around and find one that is only 20A.

Same with volts, if you expect 300V at most (open circuit, the batteries will clamp it under normal circumstances) then 400V MINIMUM should be your aim. 600V is better, 800V or 1000V are not however a disadvantage and will give you some added headroom for spikes - may be the difference between a bridge surviving or failing.

Also remember that bridges are usually rated for use in ways that are entirely unrealistic. Infinite heatsinking for example and perfect sinewave power, resistive loads etc.


[ Parent ]



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#10)
by Airstream on Mon Jun 29, 2009 at 09:19:08 AM MST

Something I have wondered about before... looking at Data Sheets for square small package bridges often they will list 'Half-Wave' input were used on rating test.

If I'm interpreting that correctly the bridge is not fed a sine waveform but a pulsing DC simulation of 1/2 sine wave to benchmark characteristics of ONE rectifier pair and then that is published as the overall bridges' spec.

If that is so the 'infinite heat sink' would probably be required when both halves of the circuit are actually seeing voltage drops and heat build up??

[ Parent ]



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#3)
by DanB on Sun Jun 28, 2009 at 08:47:26 PM MST

What you have shown there (3 of them) would be suitable for the 48 Volt 10' diameter wind turbine.  I've been using stuff like this lately - they're a bit easier and getting more affordable all the time, I often pick them off ebay:
http://tinyurl.com/mkry2e


Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#6)
by arwenvaughan on Sun Jun 28, 2009 at 09:34:44 PM MST

Nice. I'll probably order one of those then. Can't get any easier than that.

Any new ideas on terminal blocks and DPST switches too? Where would you look for these?

[ Parent ]



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#9)
by imsmooth on Mon Jun 29, 2009 at 07:29:35 AM MST

I got one of these on Ebay

http://cgi.ebay.com/Diode-Bridge-Rectifier-60A-1200V-Model-60MT120KB_W0QQitemZ180373253120QQcmdZView ItemQQptZLH_DefaultDomain_0?hash=item29ff156c00&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66% 3A2%7C39%3A1%7C72%3A1205%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

It is 60A, 1800v

this has a lot of headroom for you, and it is not expensive.
Jonathan
[ Parent ]



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#8)
by Flux on Mon Jun 29, 2009 at 12:42:46 AM MST

With a 48v machine charging a battery at gassing voltage the rectifier will see something over 120v piv. This is within the rating of a 200v bridge but if for some reason the battery becomes disconnected in a high wind then the rectifier may see 300plus volts. This is a fault condition and shouldn't happen, you may want the rectifier to survive in which case use at least 400v piv minimum. Personally under those conditions I would prefer the rectifier to blow up and short the turbine rather than let it run away.

Current rating of rectifiers is very confusing. Those single phase bridges are rated for resistive load with an average current of 35A. This requires an almost infinite heat sink to obtain it and I am not convinced that the connectors can stand 35A.

Into a capacitive load the things need de rating well below 35A. Using them for 3 phase does give you a bit more headroom but I think you are pushing things even at 3 phase to maintain much over 25A long term. The mean power of wind is well below peak turbine rating so you may be ok to 35A at 3 phase for short peaks.

I infinitely prefer stud mounted rectifiers or proper heavy duty 3 phase bridges over those single phase things. Stud mounted diodes are a challenge to mount for the newcomers. The big industrial bridges were very expensive but often crop up surplus in various places.

If you use the single phase things don't expect them to handle the 35A and if you use cheap non branded devices then the current rating can be well under the claimed figure.

Flux



Re: 10' Turbine Rectifier Parts Questions (3.00 / 0) (#11)
by Ungrounded Lightning Rod on Mon Jun 29, 2009 at 02:58:22 PM MST

This is within the rating of a 200v bridge but if for some reason the battery becomes disconnected in a high wind then the rectifier may see 300plus volts. This is a fault condition and shouldn't happen

But you treat it like it might, anyhow.  (For instance:  If your dump load dies you'll get a lot of gassing - which insulates the plates with layers of bubbles - and my boil the batteries near-dry.)  Breakdown from reverse overvoltage is a nearly instintaneous thing.  If your mill is spinning fast enough you'll get it if you have a loose battery connector and it comes open for a moment as you're tightening it.

Remember, too, that even when things are working right the reverse voltage seen by the diodes is the peak generated voltage (1.414 times the RMS voltage if the waveform is pure sine) PLUS the load voltage (which can equal peak, due to stray capacitance, if the load opens).  So you need about 3x your rated DC output voltage just for starters, to have no margin.  For margin you work up from there.

Extra breakdown voltage costs very little in price and essentially nothing in efficiency.  So I'd go with the 600V diodes if their voltage drop and current ratings are comparable to the 400s.  No way I'd consider the 200s for a 48V mill.  (Maybe not even for 12V.)

Remember that open-circuit voltage is proportional to wind speed up to furling, furling happens fast enough to prevent overheating but not to prevent overvoltage, and you want your genny wound to reach cutin voltage at at a LOT lower wind speed that it will experience in a storm.

Into a capacitive load the things need de rating well below 35A.

And battery charging is very similar to a capacitive load for this purpose:  You get high spiky currents near the peak of the waveform rather than current proportional to voltage as you'd get with a resistive load.  (Fortunately the voltage drop across the diodes goes up with the log of the current rather than linearly.  So while power dissipation goes up more steeply than current it's not the square law you get with resistors.  So the spikey-waveform penalty isn't as bad for diodes as it is for resistors.)

[ Parent ]



10' Turbine Rectifier Parts Questions | 11 comments (11 topical)
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