Removing windings from a laminated transformer core - Help! / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Removing windings from a laminated transformer core - Help!

1 2 next

Move Thread

LAN_403

GrantX

Tue Jan 17 2012, 07:14AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

I have a roughly 1.5kVA laminated iron core (shell type EI), however it is covered in a bunch of mostly useless LV windings, and a single mains winding.

My main option is to remove the coils using an angle grinder, however I feel like I'm wasting a lot of copper. I thought about separating each of the core laminations, but that proved ridiculously hard.

Should I just bite the bullet and grind all the copper off?

Thomas W

Tue Jan 17 2012, 07:51AM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

grind coppyer you dont want off, strip all your old wire you will never need and go do a scrap haul :D

GrantX

Tue Jan 17 2012, 07:56AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

Tom Williamson wrote ...

grind coppyer you dont want off, strip all your old wire you will never need and go do a scrap haul :D

Fair point, but whenever I chop up a bunch of copper wire I keep feeling I could have used it later (a stupid paranoia I guess, haha).

I guess the grinder will be the easiest way to remove all the copper, since individually separating each core lamination as delicately as possible is starting to wear down my patience...

Experimentonomen

Tue Jan 17 2012, 09:03AM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

It's still gonna be an absolute pain to rewind it with the voltage windings you want with the core in the way.

With "useless lv windings" you make it sound like its a pt from a large PA amp or something.

GrantX

Tue Jan 17 2012, 09:56AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

Experimentonomen wrote ...

It's still gonna be an absolute pain to rewind it with the voltage windings you want with the core in the way.

With "useless lv windings" you make it sound like its a pt from a large PA amp or something.

Possibly. I pulled the transformer out of a mangled piece of equipment which could have been some kind of industrial control unit, but who knows.

As for winding my own coils, I want a 240V input coil and a high-amp 12V coil for use as a generic LV power supply.

m4ge123

Tue Jan 17 2012, 01:22PM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

Unless the laminations are welded together, It's not that hard to separate them. On a 300VA core (I guess) it usually takes me about 10 minutes. Just take scissors and shove the thin part of the blade between them and push.

Experimentonomen

Tue Jan 17 2012, 06:54PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

Baking the transformer in the oven also helps softening the agents they used to bind the core to prevent hummimng.

m4ge123

Tue Jan 17 2012, 11:57PM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

Won't that stink up the whole room? Those things give off an odor just from taking them apart...

GrantX

Wed Jan 18 2012, 12:19AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

m4ge123 wrote ...

Unless the laminations are welded together, It's not that hard to separate them. On a 300VA core (I guess) it usually takes me about 10 minutes. Just take scissors and shove the thin part of the blade between them and push.

I've been using a chisel and a hammer, and believe me, those motherf%$#ing laminations require FULL FORCE hammer swings to even partially separate! I've loosened about 10 laminations out of roughly 100 or more, and I already have my fair share of cuts and bruises. :( I'm also very concerned since the chisel is doing a little bit of damage to each laminaton, I'm worried they may not fit snugly toghether again.

I want to bake it apart, but everybody flipped out when I suggested throwing the huge, rusty, smelly core in the oven :)

So I guess its the grinder, or nothing. Then I also need to deal with winding coils through the central windows of the core, which I have a feeling will be incredibly rage inducing :(

Anyway, heres a pic of the transformer sitting next to an average-size MOT

radiotech

Wed Jan 18 2012, 04:11AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The way it is done in some shops is to use an air chisel to cut the windings flush and
then a press to push out the rest. Grinding copper windings in not good. Few cutting disks
can do it safely. The insulant dusts are toxic.

An association of motor rebuilders in the US has just fought a huge battle with the
EPA to reverse some new regulations that would have put them out of business.

If the coils are not burned out you are wasting them as far as wire is concerned,
but the wire will have a compromised insulation due to dipping and baking.

As was said, they can be tapped out, however once you separate the laminated
core, you will never get it back together with the same magnetic properties it had when new.

It has been humming and heating for years and that affects the roughness of the oxide
treated surface.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob