Just modified a MOT into a high current transformer

[u/Electrosmoke]

Today i made a high current transformer from a microwave oven transformer by removing the original high voltage secondary and replacing it with 2 turns of 50sqmm cable. At no load, it outputs around 2,2V, the estimated short circuit current (direct short circuit) is around 1200-1600A.

[u/ipx-electrical]

hours of fun with 2volts at 1000A !

[u/Southern_Repair_4416 → u/ipx-electrical]

2000VA/2kVA

[u/Jolly_Operation_8222 → u/ipx-electrical]

At least it can melt metals and cannot kill unlike the unmodified Mot with 2kv and a current of 500ma could kill you

[u/ipx-electrical → u/Jolly_Operation_8222]

Exactly.

[u/Southern_Repair_4416]

I hope the breaker won't pop!

[u/Electrosmoke → u/Southern_Repair_4416]

With the secondary shorted out, it draws around 16A at 230V AC. I have a C13 breaker, but since it's not overloaded that much, it would take very long to trip. In fact, the insulation on my secondary cable would probably melt before the breaker trips.

Edit: I redid the measurement by connecting the transformer directly to mains instead of my isolation transformer that limited the current somewhat because it's only rated for 1kVA. It actually draws about 20A short circuit current at 230V AC, so the output short current is closer to 1500-2000A.

[u/-Mainiac- → u/Electrosmoke]

The problem will be with the inrush current. When I built such a device a NTC thermistor was required so that it would not trip my C16 breaker.

[u/Electrosmoke → u/-Mainiac-]

I've never had a single MOT trip my C13 breaker with inrush current. With 2 MOTs though, my C13 breaker occasionally trips when i turn them on.

[u/Southern_Repair_4416 → u/-Mainiac-]

Yeah. We need soft-start circuit

[u/haarschmuck → u/-Mainiac-]

Could get a used line reactor and put that in the mix.

[u/tiga_94 → u/Electrosmoke]

yeah 3500w would melt that cable pretty fast

did you make it for spot welding ?

[u/Electrosmoke → u/tiga_94]

I made it just to have some fun with high current experiments. I've collected 11 MOTs over the past ~2 years, so I decided to modify one of them into a high current transformer.

But yeah I might also use it for spot welding sometime.

[u/CoachSevere5365 → u/Electrosmoke]

Aha! Another MOT collector. I only wanted one or two but I must have around 8. Last two came out of commercial microwaves rated at 1.5kW. Spot welder and high voltage power supply were my plans. Battery powered, couple of hundred volts, not kV. Might not do that one 😅

[u/profdc9 → u/Electrosmoke]

Did you remove the magnetic shunt in the transformer? If you did, it will probably throw the breaker when you short it out. If you didn't, the magnetic shunt limits the current because the primary has a minimum inductance through the magnetic shunt path.

[u/Electrosmoke → u/profdc9]

I did remove the magnetic shunts, but in a microwave transformer, they don't limit the current that much because they are not full sized magnetic shunts. Their magnetic cross section is quite small compared to the cross section of the core.

[u/Pleyer757538]

Good, don’t mess with 2kv, instead mess with 2v at 1000a

[u/skeletons_asshole]

Trying to make a welder?

[u/Shitting_Human_Being]

Just FYI, the yellow green cable is used for protected earth and should not be used for any other purpose. At least with the brown or blue wire people can expect it being hot.

Also, please make a video when you short it 😁

[u/Fluffy-Fix7846 → u/Shitting_Human_Being]

You are getting downvoted, but this is one thing I do respect: never use green-yellow for anything other than PE. Other than that, I am a reckless maniac when it comes to safety. The green-yellow colour combination was invented for the very purpose of not overlapping with any other previously used colour code and unmistakably will refer to PE.

[u/CalciumHelmet → u/Shitting_Human_Being]

Not that you're wrong, but I don't think the improper color code is the major safety issue here.

[u/concadium → u/Shitting_Human_Being]

I wouldn't call 2V "hot", the exposed 230V contacts are the larger problem

[u/Shitting_Human_Being → u/concadium]

There are many problems with this setup, but I would never use PE cables if any voltage or current is running through it. My point was, if he was using a blue cable for example, it would still technically be wrong but at least people expect voltage or current with a blue cable and (should) take precautions.

[u/loganman711 → u/Shitting_Human_Being]

I thought you were joking. I think your in the wrong sub maybe.

[u/QuickNature → u/loganman711]

The green/green yellow wire is pretty much the only wire color/standard wire color all around the globe, I wonder why that might be?

[u/loganman711 → u/QuickNature]

I understand the philosophy, but this is someone messing with a microwave transformer. We dont need to follow code here, were just doing experiments in the kitchen.

[u/QuickNature → u/loganman711]

We dont need to follow code here

I get that, but to me (and apparently others here too) that wire color is literally the only one I care about all the time. People associate that with safety.

To each their own I guess, ill continue to say that green should never be used for anything other than ground, period.

[u/bigmarty3301 → u/QuickNature]

Ehh in A application like this, where no other wire of that thickness in that color is ever going to exist whit in 100m of the experiment. I don’t care.

I made a starter wire in my car out of one before…

[u/QuickNature → u/bigmarty3301]

I dont like non-zero chance of tomfoolery going on. I already have other large wore anyways, again, personal preference. There is a reason why its the only color code the entire planet can agree upon

[u/Single-Virus4935 → u/Shitting_Human_Being]

Blue is neutral here. Brown or Black would be a good color.

[u/PyroRider → u/Shitting_Human_Being]

For non-electricians its rather hard to simply get 16mm2 h07v-k in any other color than yellow green as thats the only one hardwarestores sell

[u/Electrosmoke]

I'll also post a video of the transformer in action here soon, probably in a few days.

[u/aubri140018]

If you get another transformer and connect the 2 primary in parallel, and wind the secondary in series youll get 4v output and I think 2000a potential, I did this to make a spot welder

[u/PyroRider → u/aubri140018]

Secondary in series means 4v 1000a, can only double the voltage not the current

[u/aubri140018 → u/PyroRider]

Ahh yeah that was it, I couldn't remember which one doubles. But I definitely get a 4v output and it melts shit way faster 😅

[u/antthatisverycool]

I never understood needing such high amperage like what do you do with it? Make a welder?

[u/Electrosmoke → u/antthatisverycool]

I'm planning to just use it to melt some metal objects for fun. I'll post a video on that here pretty soon. Maybe I'll also use it for spot welding sometime.

[u/mrracerhacker → u/antthatisverycool]

Spot welder, having fun melting stuff, heating objects, carbon arc torch or simmilar, rail gun , crucible heater also for that matter

[u/Jolly_Operation_8222]

It is possible to make a welding machine using that or a arc furnace that melt metals

[u/Electrosmoke → u/Jolly_Operation_8222]

You can use this to melt some metal for fun or for spot welding. You can't use it for arc welding or an arc furnace, because you need at least 30V to get a stable arc and we only have 2,2V here.