If the metal epoxy is conductive you will create a shorted turn which may get very hot and /or cause the primary current to be higher than it should be. It will depend on how conductive the epoxy is.

Les.

Hi Les, if that is the case, how do they get away with putting a bead of weld on microwave transformers and induction motor stators? I've got a couple of each that have a weld bead connecting all of the laminations that way. I too thought it would act like a shorted turn but doesn't seem to.

Honestly, I don't know how to go about explaining that but the transformer cores have been weird in my experience. My thoughts are that it's not too big of a deal if a few of the sheets touch at small points. Otherwise, it would be very hard to mass produce transformers that have alternating E & I sheets because some of them are bound to scratch off the lamination at points when forcing in the last couple sheets

 

Otherwise, it would be very hard to mass produce transformers that have alternating E & I sheets because some of them are bound to scratch off the lamination at points when forcing in the last couple sheets

I'm not to sure about that point. As a machinist/die maker my whole adult life, one of the hardest things out there is the scale or oxide on mild steel. Not to hard if you can get under it but the surface is very hard, even to a grinding wheel. And both transformer laminations and stator laminations are purposely oxide coated when being made, to form an insulating oxide layer on them. And that layer is very hard to scratch.

 

I'm not to sure about that point. As a machinist/die maker my whole adult life, one of the hardest things out there is the scale or oxide on mild steel. Not to hard if you can get under it but the surface is very hard, even to a grinding wheel. And both transformer laminations and stator laminations are purposely oxide coated when being made, to form an insulating oxide layer on them. And that layer is very hard to scratch.

If my understanding is correct, the transformer core sheets aren't focused on electrical conductivity in the first place. The magnet wire making up the coils is already insulated, so electricity isn't even passed into the core. Instead it's to control magnetic flux. But I'm pretty damn new to this, so the majority of my "knowledge" comes from the school of Google. Very little is as a result of actual experience. But I am busting my ass accumulating as much experience as possible. I've got a DC arc welder and DC bench power supply that I'm nearly done with along with this iso transformer (I hope). And then a lathe and mill (possibly converted to CNC) much younger in their production timelines. The ones closer to completion are likely to be most useful, but I think the latter ones will be the most impressive. I've also got a lot going on with a foundry build and an assortment of torches, some work with the foundry, and some for other applications. The waste oil + forced air + O2 torch is probably the most complex thus far. But it's cool in the fact that I never need to go buy fuel as with my forced air + propane torch before (this is because the waste oil can always be acquired free from a kitchen or garage, and I've built my own O2 filling station from an O2 concentrator, an O2 compressor, and the ripoff-priced fill nipple/check valve for the compressor converted into a universal fill valve

 

If my understanding is correct, the transformer core sheets aren't focused on electrical conductivity in the first place.

It's not that they conduct the electricity in the coils, but something called "eddy current". That is the reason for the oxide coating on the laminations, to reduce eddy currents. Eddy currents cause heat, above what the coils do.

 

It's not that they conduct the electricity in the coils, but something called "eddy current". That is the reason for the oxide coating on the laminations, to reduce eddy currents. Eddy currents cause heat, above what the coils do.

Eddy currents are a product of magnetism, no? And the laminations don't reduce eddy currents as a whole. They reduce the size of the eddy currents, resulting in an increase in the quantity of them. So while that statement isn't technically incorrect, the opposite is also just as true

 

I know it's been a while since my last update and I apologize for the delay. It's difficult to find a good time that I can blow a breaker around my house. So in the meantime, I added some things. primarily terminals, and all from the salvage stock. The only new components are the band clamps. All else was recycled. Here's a few pics:

The first is the transformer(s) and the additional output jacks. The second is the isolated outlets. And the third is the power cable, power switch, and inline circuit breaker. Probably the only part I leave well enough alone is going to be the additional output jacks and inline circuit breaker. I'll likely pick up a 4-plug wall outlet and plate for it, probably add a 2 plug outlet that I will connect to the ground cable on the input just to have that option. But to answer the question anybody still following probably has, the buzzing is noticeable but not loud, and more importantly, it works just fine. Now I'm going permanently attach the cores and bathe the coils in coil dope to hopefully kill the noise. But it's not that big of a deal. And it will be nice to no longer need to worry about blowing a breaker when I test something.

Moral of the story: 2 nearly identical EI core transformers into one EE core isolation transformer was a success. Now I just gotta make it look decent and it's good to go. Now I'm going to shift my focus to finishing my stick welder as well as finishing the conversion of my 3d printer to use a water-cooled, bowden-fed quad color/material hotend (as well as swapping out the steel linear rods for carbon fiber tubes. The weight difference is MASSIVE)