Electronics > Beginners
Where to buy an isolation transformer ?
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Cliff Matthews:
Out where you live, you can make a constant duty 500-watt unit for under $150 with some low-tech work and get a ship-load of spare parts to boot. We've talked about MOT's before, so be patient with this old guys rambling:

1) Get 4 large MOT's by posting a free kijiji want-ad saying "deliver me your big old micro-wave and get $20 cash" (buy 5 or 6 to make sure you get decent size matching). That's the fun part in getting all the goodies.
2) Use a hack-saw to cut off one side of all the secondaries and knock them out of the other side (do not cut the primaries..)
3) Screw all 4 MOT's to a piece of plywood in a square formation with the primary terminals facing outward.
4) Wire the primaries in series and attach the usual fuse/switch and power cord to the the line-side. Wire the secondaries to a good quality DPDT switch (so you can have a useful 60v/120v output in series or parallel) and attach a fuse and receptacle.
5) Buy some #4 welding cable at Princess-Auto on 410 Stavanger, and neatly stuff all new secondaries full in a loop (same turn quantity on each and same turns direction).

Once everything's running the way you want (including maybe some switches for secondary taps to control output voltages) run it for a few hours on various loads and then transfer it to a box. Of course, this is not a project for well-healed or lazy types, but if you have the time it'll be fun.

chemelec:
Somewhere I have a 110VAC Hammond Isolation transformer and you could have it for Free, Other than the Shipping cost.
Not sure on the wattage, But Should be in the 300 to 500 watt range.
Just need to Find it.

I am in BC Canada
CCB:
Builders used to use isolation transformers for outside work like mixing concrete, are these suitable? Nowadays I guess they use RCD devices.

Also how about 2x UPS transformers with the secondaries connected?
lordvader88:

--- Quote from: rhb on August 14, 2018, 03:43:54 pm ---
--- Quote from: lordvader88 on August 14, 2018, 12:42:38 pm ---Well see I did that, I have both primaries on 1 core. People said I should add another 20% to each coil, so as to overcome the saturation/heat issues with MOTs. And then get it welded back together, hopefully I could find someone/shop to do it for free or $5, it would take them 5 seconds.

So thats about 15/20ft of 14 gauge wire, times 2. And I haven't gone looking for that yet. I might be able to get 14/1 wire for $0.30/ft

That would do for now, if I can get the wire for cheap and welded for cheap.

--- End quote ---

There's no need to weld it.  That's just done to avoid the expense of screws.

Putting the primary from a 2nd transformer will provide isolation, but you might not get the voltage you want if they are not identical.  However, if you're using it to isolate an autotransformer, it may not matter.

--- End quote ---
Well I'd have to bolt it back together super tight tho, but yeah I never even considered that because I'm hoping some garage would just do it for free, or I'd offer $5

Right now it's like a 60Hz clapper with a big loud heavy lid
lordvader88:
Hi    Cliff Matthews, thanks but thats a lot more work and overall would weigh a lot more. And I'm impatient so I'm going to buy 1. But I'm going to use the MOT IT I've almost finished.....I'm assuming MOT's must have very good insulation on them. And 14/1 14/2 wire that I add should be just fine, why wouldn't it be ? I'm not planning to use this in a lightning storm. (And sadly we barely get any)

What % of people on here have an IT ?



--- Quote from: chemelec on August 14, 2018, 06:18:35 pm ---Somewhere I have a 110VAC Hammond Isolation transformer and you could have it for Free, Other than the Shipping cost.
Not sure on the wattage, But Should be in the 300 to 500 watt range.
Just need to Find it.

I am in BC Canada

--- End quote ---
Well thanks and I'd gladly pay shipping for such a thing, if I could pay with paypal for safety, if u could make it a private sale on ebay.ca, I'd cover their charge to u as well, thanks.
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