Simple three core transformer shows moderate COP

[Jack Noskills]

I made this three core trafo almost one year ago. I used litz wire wound around nanoperm core. With 100 watt input I got about 200 watt output, this was measured using True RMS meter and further confirmed using two toasters and light bulbs.

My idea was that by adding more output cores I would get out better COP. It did not happen so I stopped development. Just recently I realised that I should have used bigger output core, not multiple of them. I have already reused my cores for other purposes so I cannot further test this.

If you have three 1:1 trafos or MOTs you can test this yourself easily. If you have MOTs then put one of them in stepup mode and connect third MOT so that secondary of it is shorted and you take power from MOTs primary. Picture of the connection is shown below, note the right most MOT has equal coils so it is not exactly a MOT. You can try MOT also here if you dare. If you have small trafos and big one then use small ones as primary and bigger one for output core. Maybe you get better COP but I haven't tested this. Polarities needs to be correct and it is easy to set it up. First connect everything as shown but leave secondary of output core unconnected. Put load on, then short the secondary. If it is connected correctly output power is increased, if it is wrong input power is increased. In my setup input power also decreased when power was taken.

I don't ask people to start buying trafos as confirmation is needed first. So if you have suitable trafos available then do the simple test and contribute your findings here for all to see. It will take only few minutes of your time.

[SchubertReijiMaigo]

Interesting setup, you use three 1:1 trafos right ?
"Put load on, then short the secondary. If it is connected correctly output power is increased, if it is wrong input power is increased. In my setup input power also decreased when power was taken."
OMG, shorting the secondaries ? You mean conected in antiphase ?
You are in 120 or 240 VAC ?

[Jack Noskills]

Interesting setup, you use three 1:1 trafos right ?
"Put load on, then short the secondary. If it is connected correctly output power is increased, if it is wrong input power is increased. In my setup input power also decreased when power was taken."
OMG, shorting the secondaries ? You mean conected in antiphase ?
You are in 120 or 240 VAC ?

I used three 1:1 trafos, 280 meters of 0.31 mm wire per coil using 80000 permeability nanoperm core. I had Litz wire so primary and secondary were interleaved. The output trafo is in bucking mode so that the coils feed each other. I shorted the secondary between the trafos and it is safe. I used 220V/50 Hz grid as AC source and when I started testing I had current limiter bulbs there. Once I obtained power levels I removed the limiter and did amp measurements without it.

[SchubertReijiMaigo]

The trafos wasn't saturated ? Because when you saturate it and put loads on secondary the input current decrease and some meter can be fooled by the third harmonic...

[Jack Noskills]

The trafos wasn't saturated ? Because when you saturate it and put loads on secondary the input current decrease and some meter can be fooled by the third harmonic...

Don't know about saturation. I observed first using lamps and lamp brightness went down. Later on I measured with true RMS meter and it confirmed what lamp showed. If you have trafos you can use then 'just do it' lol.