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Registered Member #627
Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32
Hi all.
When rewiring a MOT secondary with just a couple of turns of thick wire for a high current, low voltage output, should I remove the shunts in the transformer? I see some people say yes but have also seen people leave them in when doing this. Thoughts?
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
The shunts are extra core material that will absorb some of the magnetic flux induced in the transformer by the primary windings, effectively lowering the amount of current that can drawn from the secondary, thus protecting the primary winding. If you remove them and later add them again, remember to maintain the same isolation between shunts and transformer.
A MOT is by design on the edge of self destruction, leaving in the shunts will make you able to have longer run times but with lower secondary output current, wise versa without shunts.
Registered Member #627
Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32
OK, well I took them out but I bent them up in the process; I don't think they will be going back in! Mads, do you mean they must be insulated from the main core?
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Sparkie wrote ...
OK, well I took them out but I bent them up in the process; I don't think they will be going back in! Mads, do you mean they must be insulated from the main core?
They can be in contact with the outer core, but they must not make a connection between the outer and inner core, that would make a smaller "window" for the magnetic flux to run in.
Registered Member #627
Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32
Thank you, I did notice the card insulation around them. Thanks for the help!
Managed to get 300A with a ballast in the primary (2kW heater) but the 8AWG wire warms up very fast like this. I must get some better wire for it. Fun though, and safer than the old HV secondary :)
Banned on 1/22/2011 for repeated rule violations after multiple warnings. Registered Member #3299
Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220
take them out if anything you have more room for windings
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Sparkie wrote ...
Will do Patrick. When I get a better transformer and some larger cable, I'll add it here. Cheers!
TY! I will have 8 Large MOTS here soon, I plan to rewire them for 240 in, 10-24V out, at 1.5~2kW so that should be about 80 or so Amps out for each of the 8 Mots. I'm trying to make a "Solid Oxide Fuel-Cell Stack Emulator" and thats what I call it, as I dont know what else to call it.
I would use a car battery, but the 10v is too low, 20V is too high. So I cant really series-parallel them to be useful. As I really need 15-16.5VDC @ ~400Amps, for a classified-super secret progam, Ill post soon though. anything you can post would be useful.
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MOT high current secondary. Shunts?
