Smoothing Capacitor

[BruceM]

Your projects are always interesting and always done well, Geno. Very impressive, and I get to learn a lot from your designs and work. Your system is more on the  scale of my homebrew off grid homestead.  I too subscribe to the "less is more" school in off grid power.  There's not much to be learned for me from a big commercial gear install except shock ($) and awe. (Some very capable gear out there which is impressive in design.)

The UPS efficiency is probably quite decent with a load, no load is a problem in design  relying on inductive filtering, which in a highly cost-competative UPS can be ignored to save cost.

A small fan on the transformer might be the most effective cooling aid. A way to switch off the UPS unit automatically when there's no load could be done, if you need it operationally.  But you're probably way ahead of me on that angle.

[Geno]

Thanks for the compliments Bruce.

I made all the changes and put my ups online to supply the house with clean power.  Every thing went well for about 15 minutes and then I watched the rectifier smoke. 80amps/1000 volts my ass. It was right after I pushed the Flexmax 60 to 32 amps charge current. The heat sink on the rec never even got above 100°F. I always thought that thing looked puny for the kind of power I wanted to push through it. Anyone think these will work?

Thanks, Geno

[Crumpite]

Thanks for the compliments Bruce.

I made all the changes and put my ups online to supply the house with clean power.  Every thing went well for about 15 minutes and then I watched the rectifier smoke. 80amps/1000 volts my ass. It was right after I pushed the Flexmax 60 to 32 amps charge current. The heat sink on the rec never even got above 100°F. I always thought that thing looked puny for the kind of power I wanted to push through it. Anyone think these will work?

Thanks, Geno

Geno,

Yes, the second picture of rectifiers looks a lot more like it. I'd guess the first bridge rectifier was manufactured to either Chinese or Indian standards.

The price on those stud mount units seems really high - have you looked at replacement rectifiers for/from auto alternators ?
The last time I looked they were pretty reasonable due to high volume production.

I'll take a look at my sources and see what I can come up with.
Daryl

[BruceM]

Hi Geno,

The bridge diode shown first is at best a 30 amp unit.  And I would recommend that you stay at 60% of rated capacity.  No way that type can handle 80 amps.  I suspect a typo by some clerk. 

The price listed for the stud type unit is ridiculous.  Try Digikey, Mouser, Allied, etc.  You can parallel two bridges like the one you fried if you need to, each will see half the current.   Be thinking about a  nice big heat sink, and thermal grease.

[Crumpite]

Ok Folks,
I thought I could find cheaper and/or better diodes:

http://www.mouser.com/Semiconductors/Discrete-Semiconductors/Diodes-RF-Signal-Switching-Power/_/N-6hpde?P=1z0y2h5Z1z0vyks

and

http://www.digikey.com/

Mouser doesn't have a minimum order, so I listed it first.
The surplus houses seem to be more expensive than new right now (surplus places do that at times...)

If you're in a different area than the US, there are other places that you can deal with.

BruceM is very correct about the size of the heatsinks and the thermal grease !

Hope this helps a bit,
Daryl

[mike90045]

I think this would be a solid bridge unit
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CC1653-ND
but pricey.  When I buy a part, I want to know what the mfg part is, otherwise, you are likely getting floor sweepings from libertye-online. Digikey has a good parts search,
here's a real nice one, real specs:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=85HF80-ND
DIODE STD REC 800V 85A  low fwd drop gives less watts to dissipate

[Geno]

Thanks for the tips guys. I have a bigger heat sink for my next move.
I found these at $2.70 if I buy ten.
http://www.mouser.com/ProductDetail/Ruttonsha/85HF60-1-4-UNF/?qs=sGAEpiMZZMtvcUztdGSumD0SzMkM1HL%2fUv37H1wx944%3d
Overall and Current Rectifier Setup. I still have some cleanup to do but it's pretty close to the final config.

Thanks, Geno

[BruceM]

Geno- don't forget to order some mica isolators for your stud type rectifiers. 
Your setup looks very good, your original bridge rectifier heatsink mount was decent.

Just remember the watts to be dissipated are calculated by diode voltage drop times the max amperage. Standard high current, glass passivated diodes like the stud types you've picked have a 1.3V drop.  At 60 amps, that's 80 watts of heat you've got to dissipate.  BIG heatsink!