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Author Topic: Changing AC to DC  (Read 2215 times)

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patty3

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Changing AC to DC
« on: August 25, 2004, 11:42:57 PM »
Can anyone tell me where I can find rectifiers powerfull enough to change an AC welding machine to a DC welding machine? 250 amps with 75 to 80 OCV.
« Last Edit: August 25, 2004, 11:42:57 PM by (unknown) »
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thunderhead

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Re: Changing AC to DC
« Reply #1 on: August 26, 2004, 02:24:11 AM »
International Rectifier 70U20s do 250A @ 200V.  Farnell carry them "while stocks last" and will export them to the USA.  Be warned: they're UK30 (maybe $55) each.  Try www.farnell.com.
« Last Edit: August 26, 2004, 02:24:11 AM by (unknown) »
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tecker

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Re: Changing AC to DC
« Reply #2 on: August 26, 2004, 03:21:02 AM »
Parallel a bunch of cheaper ones with heat sinks Digikey has a good selection.
« Last Edit: August 26, 2004, 03:21:02 AM by (unknown) »
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drdongle

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Re: Changing AC to DC
« Reply #3 on: August 26, 2004, 05:40:22 AM »
Check with Mouser Electronics www.mouserelectronics.com


Carpe Vigor


Dr.D

« Last Edit: August 26, 2004, 05:40:22 AM by (unknown) »
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Opera House

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Re: Changing AC to DC
« Reply #4 on: August 26, 2004, 11:26:19 AM »
25A bridge rectifier blocks are pretty cheap and easy to mount on a sheet of aluminum. Just use a dozen of them.  Fuse each AC input and this will act as a resistor to load balance the current to each rectifier.  I think more smaller diodes is more reliable.  A friend bought sub grade SCRs and just gated them on all the time to act like diodes.  Check out Ebay.  They often have a good selection of this stuff, new and pullouts.
« Last Edit: August 26, 2004, 11:26:19 AM by (unknown) »
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BrianK

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Re: Changing AC to DC
« Reply #5 on: August 26, 2004, 11:37:21 AM »
I have right now an electric train carnival ride that runs on dc power I opened up the control box to find that it is powered by no more than an adjustable resister (VERY Large) and a bridge rectifier that you can buy at radio shack. All this setup does is change the 120v ac into adj. 0-120v dc to power the train


   

« Last Edit: August 26, 2004, 11:37:21 AM by (unknown) »
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Joseph Turrisi

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Re: Changing AC to DC
« Reply #6 on: August 26, 2004, 06:27:41 PM »
Surplus center sells diodes rated at 150 volt 400amps for $16.95 check it out at www.surpluscenter.com
« Last Edit: August 26, 2004, 06:27:41 PM by (unknown) »
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RobC

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Re: Changing AC to DC
« Reply #7 on: August 26, 2004, 08:24:45 PM »
Iv'e picked quite a few at the scrap yards in old welding equipment. Scraped locomotives have them also.
« Last Edit: August 26, 2004, 08:24:45 PM by (unknown) »
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Opera House

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Re: Changing AC to DC
« Reply #8 on: August 27, 2004, 08:20:56 AM »
Checked Ebay (serch diode)and you can get four 35A 1,000V bridges for $8.  8 to 12 of these would be fine.  Don't skip on voltage because you will get some good inductive kicks.  Instead og fuses, you can hook a foot of #18 wire to each terminal for load sharing. Provide some support th the wires so they can burn out in the event of a short.
« Last Edit: August 27, 2004, 08:20:56 AM by (unknown) »
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