Eva,
Forgive me if this question has already been answered elsewhere, but what is the application that requires 15V at 120A?
That appliance has to have a 0.1 ohm total internal resistence, including connecting cables and connectors.
Heck, I short my ohmmeter probes together, and get a 0.2 ohm reading. It's not easy to guarantee sound connections under 0.1 ohm.
The slightest layer of oxide between contacts could cause heating, causing more oxide build-up, increased resistence, more heating, etc, and contact thermal runaway.
Any contact point that measures 0.01 ohm will dissipate 180W...
Gaaaa!! (Run!, Run!)
I'm sure you've taken all precautions, otherwise your project would not have come this far, but this trancends electronics now. This is power plant engineering.
Forgive me if this question has already been answered elsewhere, but what is the application that requires 15V at 120A?
That appliance has to have a 0.1 ohm total internal resistence, including connecting cables and connectors.
Heck, I short my ohmmeter probes together, and get a 0.2 ohm reading. It's not easy to guarantee sound connections under 0.1 ohm.
The slightest layer of oxide between contacts could cause heating, causing more oxide build-up, increased resistence, more heating, etc, and contact thermal runaway.
Any contact point that measures 0.01 ohm will dissipate 180W...
Gaaaa!! (Run!, Run!)
I'm sure you've taken all precautions, otherwise your project would not have come this far, but this trancends electronics now. This is power plant engineering.
Big car amps comes to my mind first. 8mm bolts with nuts make suitable output connectors providing low resistance. Or welding machine connectors, they are simple and can take anything up to 500Amps.Joseph Hynes said:
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I have seen some 24v 130A SMPS-welders and they are supprisingly small, about size of 2 atx-power supplies. Craziest thing is that they are 160khz 2-transistor forward desings, bit unusual choice for smps in 3kW class.
Even if they look thin or rudimentary, all the wirings and connections in the secondary side are in the sub-miliohm range, otherwise they would melt badly (as this loose one did : http://www.diyaudio.com/forums/showthread.php?postid=714975#post714975 )
Remember that copper wire DC resistance is approx : 0.017*L/S where L is length in meters and S is cross-sectional area in square milimeters. Thus one meter of 6mm^2 wire yields 2.8 miliohms DC resistance and only 40 watts dissipation for 120A DC. This produces 400 miliwatts per centimeter that are enough to get the wire at 60ºC in free air but not enough to melt the insulation.
The wiring of the synchronous rectification board employs two 6mm^2 wires in paralell, so they are dissipating only 100mW per centimeter at full load, they get only mildly warm to the touch.
Remember that copper wire DC resistance is approx : 0.017*L/S where L is length in meters and S is cross-sectional area in square milimeters. Thus one meter of 6mm^2 wire yields 2.8 miliohms DC resistance and only 40 watts dissipation for 120A DC. This produces 400 miliwatts per centimeter that are enough to get the wire at 60ºC in free air but not enough to melt the insulation.
The wiring of the synchronous rectification board employs two 6mm^2 wires in paralell, so they are dissipating only 100mW per centimeter at full load, they get only mildly warm to the touch.
This project is almost 4 year old now. I still keep the breadboards and separate PCBs on a big piece of wood but the files for the PCBs are in the old DOS Tango PCB format (without schematics) in another computer, and there are no schematics for the breadboards (control circuit) either.
Anyway, nowadays I would do many things in different ways and with different newer components.
Now I'm working with SMD and double sided PCB (and soon four layer) and a much wider selection of components. I would like to bring back this project to the workbench in the future and make it ultra compact without losing much efficiency, but I'm currently busy with a commercial high power class D amplifier project.
Are you interested in how I achieved some particular thing in the old prototype?
BTW: Some of the files linked in my posts disappeared because I changed web server. If you can find out the name of the missing files by looking at forum html source code, I may be able to restore them.
Anyway, nowadays I would do many things in different ways and with different newer components.
Now I'm working with SMD and double sided PCB (and soon four layer) and a much wider selection of components. I would like to bring back this project to the workbench in the future and make it ultra compact without losing much efficiency, but I'm currently busy with a commercial high power class D amplifier project.
Are you interested in how I achieved some particular thing in the old prototype?
BTW: Some of the files linked in my posts disappeared because I changed web server. If you can find out the name of the missing files by looking at forum html source code, I may be able to restore them.
Eva, with some modifications, this design looks like something the EV builders would like in order to power 12v automotive devices from the large battery packs. Just add some different versions with nominal input voltages from 72v to 200v, fix the current limit at its full capability, have the output voltage able to switch between 13.8v and 14.4v under logic control, and design it so leakage current when off is minimal if it is used as a charger.
Wow Eva. First, let me compliment you on all your work. You're definitely a true DIY'er, and not one of those "all 'wisdom,' no projects" kind of guys.
Let me ask you, any reason you didn't use 40V, 150A (or more) Schottky diodes for secondary rectification?
Also, any reason you didn't use a COTS (commercial, off-the-shelf) 150A current shunt within the output loop to monitor current?
Not to impugn your work, but it's what Sorensen/Elgar does on their DCS-series 1KW & 3KW commercial switching supplies. I have a few of their 1KW models (thank you eBay!), plus the schematics, and their designs are elegantly simple, yet robust.
When I worked in professional car audio, in order to test our 800W monster audio amp, we used 3 Pioneer Magnetics 5V, 300A switching power supplies connected in series. Each was trimmed down to 4.6V to give us 13.8VDC to simulate a car's electrical system. Cool stuff!
Thanks,
Paul
Let me ask you, any reason you didn't use 40V, 150A (or more) Schottky diodes for secondary rectification?
Also, any reason you didn't use a COTS (commercial, off-the-shelf) 150A current shunt within the output loop to monitor current?
Not to impugn your work, but it's what Sorensen/Elgar does on their DCS-series 1KW & 3KW commercial switching supplies. I have a few of their 1KW models (thank you eBay!), plus the schematics, and their designs are elegantly simple, yet robust.
When I worked in professional car audio, in order to test our 800W monster audio amp, we used 3 Pioneer Magnetics 5V, 300A switching power supplies connected in series. Each was trimmed down to 4.6V to give us 13.8VDC to simulate a car's electrical system. Cool stuff!
Thanks,
Paul
Sorensen 1KW & 3KW Schematics
If anyone is else is interested in the schematics, I have zipped them up into 2 x 900KB files and can email them out. Or, if anyone has their own site and wishes to post them for non-commercial, DIYAudio use, I can email them to you.
By the way, these schematics were given to me for free by Sorensen because I own some of their products and requested them. I post them just for general knowledge and educational purposes, and not for any form of copyright infringement. Also, don't attempt to build an off-line, high-power SMPS without a lot of knowledge of safety, device selection, and regulatory considerations. A cool power supply project is not worth dieing over!
If anyone is else is interested in the schematics, I have zipped them up into 2 x 900KB files and can email them out. Or, if anyone has their own site and wishes to post them for non-commercial, DIYAudio use, I can email them to you.
By the way, these schematics were given to me for free by Sorensen because I own some of their products and requested them. I post them just for general knowledge and educational purposes, and not for any form of copyright infringement. Also, don't attempt to build an off-line, high-power SMPS without a lot of knowledge of safety, device selection, and regulatory considerations. A cool power supply project is not worth dieing over!
Pictures missing, links...
1st page:
http://eva.eslamejor.com/buckbrd0.gif
http://eva.eslamejor.com/buckbrd1.gif
This are 2 pictures, files missing from server..
Next post...
http://img311.imageshack.us/img311/9072/100a3c9ys.gif
http://img311.imageshack.us/img311/7682/100a3d8qs.gif
http://img311.imageshack.us/img311/2371/100a3e8rb.gif
This 2 could be hard to know what were they...only if you do
So do you think, you will redo this project, do it diffrently or do it at all?
1st page:
http://eva.eslamejor.com/buckbrd0.gif
http://eva.eslamejor.com/buckbrd1.gif
This are 2 pictures, files missing from server..
Next post...
http://img311.imageshack.us/img311/9072/100a3c9ys.gif
http://img311.imageshack.us/img311/7682/100a3d8qs.gif
http://img311.imageshack.us/img311/2371/100a3e8rb.gif
This 2 could be hard to know what were they...only if you do
So do you think, you will redo this project, do it diffrently or do it at all?
Hi eva this is a very interesting project in terms of educational value, can someone please updated this thread and keep the circuit diagrams, images ect... archived please im following professional guidelines and practices this is a rather good thread to learn from. PCB layouts are nicely done with pride 
Thanks
Thanks
Last edited:
Hello Luka, please post again the files, they are missing... sorry my english.
Thank you.
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