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shawn

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Joined: 30/03/2010
Location: New Zealand
Posts: 210

Posted: 09:29am 18 May 2011

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Need a little help!
my small mill uses 3 block type rectifiers they are the 35 amp type they work fine.
my new mill will have far more current can I use six or twelve joined together to increase the capacity?

Thanks shawn

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 10:58am 18 May 2011

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Hi Shawn

I think you would be better using this rectifier.

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=190508 163152&ssPageName=STRK:MEWAX:IT#ht_3034wt_905

Item number: 190508163152

I have found that for a bit of serious power these stand up better

Bob

Foolin Around

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 12:19pm 18 May 2011

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Yeah Bobs right, you can buy 3 phase rectifiers very cheap these days, and its a easier way to go. But to answer your question, yes you can connect more than one rectifier in parallel to give a higher rating rectifier.

There is a small catch though. No two components are ever exactly the same, manufacturing tolerances mean two components with the same part number can perform slightly differently. Normally this isn't a problem, until you ask them to work in multiples. Take two rectifiers, both 35 amp types, same part number. One of them might have a bias voltage of 0.61, and the other 0.62 volts. That 0.01 voltage difference means one will switch in before the other, and if you are exceeding the individuals rectifiers current capacity, the chances are its going to fail. While together they could handle 60 or so amps, one of them is going to be severely stressed with every AC cycle.

The solution in this case is pretty simple, add some resistance in line with each rectifier. Not much, in fact a few cm of wire will do, just enough to give each rectifier a little bit of series resistance between it and its mates.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

shawn

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Joined: 30/03/2010
Location: New Zealand
Posts: 210

Posted: 04:16am 19 May 2011

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Thankyou Bob / Glenn
My electrckery training all came from TV !! Catweasel now he new his stuff

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 01:40pm 19 May 2011

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Hi Shawn

remember the only silly question is one thats not asked.

My Question:- Who or what is Catweasel.

All the best

Bob

Foolin Around

shawn

Senior Member

Joined: 30/03/2010
Location: New Zealand
Posts: 210

Posted: 07:02pm 19 May 2011

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He was a TV character from the seventies. I was still in nappies but my wife used to watch it and recently got it out on dvd for the kids.
We all were mesmerised for hours

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 05:16am 20 May 2011

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AHH

The things I have missed in life.

Bob

Foolin Around

grub
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Joined: 27/11/2007
Location: Australia
Posts: 169

Posted: 09:23pm 20 May 2011

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Catweasel, Dinges (whatever happened to him?) used to use him as his icon before he changed to a muppet.

niall1

Senior Member

Joined: 20/11/2008
Location: Ireland
Posts: 331

Posted: 10:32pm 20 May 2011

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we had catweasel here too ....very very strange program going on there ..

we also had the "the magic round about" .. (puppet show)....
i think ..and not sure about this.....that some of the bbc producers of show later admitted in retirement ...lets say ...to being slightly influenced by certain induced states of mind at the time ...

...

they just dont make kids programs like they used too.......

Edited by niall1 2011-05-22

niall

Xmaswiz
Regular Member

Joined: 14/04/2011
Location: United States
Posts: 69

Posted: 04:52pm 27 May 2011

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shawn said Need a little help!
my small mill uses 3 block type rectifiers they are the 35 amp type they work fine.
my new mill will have far more current can I use six or twelve joined together to increase the capacity?

Thanks shawn

also check this site
http://suntekstore.com/3-phase-diode-bridge-rectifier-40a-10 00v-sql40a-.html

they have some higher power units as well, and the 6 of the above that I have ordered all seem to work as advertised.

this link shows all the units they currently have. they may have free shipping as well (they did for USA) http://suntekstore.com/search.html?keywords=3+Phase+Diode+Br idge+RectifierEdited by Xmaswiz 2011-05-29

Santa Maria, CA.
Noel

sparkey

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Joined: 15/06/2011
Location: Australia
Posts: 819

Posted: 07:48am 14 Aug 2011

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you canrnt realyy wire up bridge rectifiers in paralell cause you need load resistorsv ,,true i have seen 12 35 amp bridge rectifiers in paralell but with the actul doping of ever junction not being the same some rectifiers will work harder than the others but i have seen them wired in paralell...

technicians do it with least resistance

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