wiring transformers

[glinjik]

Hi can someone help me out with wiring transformers together I have 4 тп121-7 transformers 220/12v 0.36a what I'm trying to achieve is 24v 0.66a I don't want to wire incorrectly and fry them thank you in advance

[TimFox]

I don’t usually approve of parallel connection of transformer secondaries, but this process should work.
Start with two transformers.  Wire the primaries in parallel, and connect only one end of the two secondaries together.  Measure the voltage between the other ends:  if 24 V, do not connect those ends together, but change the end of one secondary to connect to the other.  If near zero, you can connect those ends together to obtain a 12 V, 0.72 V composite transformer.
Repeat this process with the other two units to obtain another 12 V, 0.72 A composite transformer.
Now wire the two composite primaries in parallel (4 windings), connect one end of each composite secondary together, and measure the voltage between the other ends.  If 24 V, you have a 24 V 4-unit composite transformer, otherwise change the connection between the two 2-unit composite secondaries and re-measure the voltage.
Is this complicated process worth it?

[glinjik]

thank you for you reply its really an experiment more than anything useful a little more knowledge gained where i live its difficult to obtain parts components so re use everything i just happen to have these 4 laying here and itchy fingers lol

[Paul Rose]

TimFox had everything right, but sometimes a picture helps.



All 4 primaries are in parallel.
Tr1 and Tr2 secondaries in parallel, forming one "double current" 12v transformer.
Tr3 and Tr4 secondaries in parallel, forming another "double current" 12v transformer.
Those pairs have secondaries in series, forming 24v transformer.

"Phasing dots" in schematic show which leads need to go together. 
To figure out phasing on your actual transformer, do what TimFox said (but sometimes wire color can give you a clue).

[bob91343]

You can't do what you want.  According to your first post, you want double the output power that the two transformers can deliver.  In other words, you can increase the current at 12V or you can get the same current at 24 V.  But not both.

[Paul Rose]

In other words, you can increase the current at 12V or you can get the same current at 24 V.  But not both.

But he said that he had 4 transformers.
Why won't it work to use pairs to double current, then both pairs to double voltage?

[MosherIV]

Yes Paul Rose, you had it right.
Parrallel 1 pair of transformers to get double the current.
Then put 2 pairs in series to get double the voltage.

Think of it like parrallelling floating psus to double the current (assuming they have identical voltage)
Then joining floating psu in series to double the voltage.

[bob91343]

Sorry I guess I missed the part about 4 transformers.  Sure that would work great, especially if all four are the same part number.  If not, you will have to deal with circulating currents.

[glinjik]

all transformers are тп121-7

Технические параметры
Выходное напряжение, В12.5
Выходной ток, А0.36
Мощность, Вт4.5
Вес, г160
technical parameter
output 12,5v
output 0.36a
weight 160g

[glinjik]

Мощность, Вт4.5
strengnth 4.5 watt