Good day, I'm thinking of building a 12 V DC power supply, using transformers removed from LV lighting sustem.
They are 120 V primary 12 v 5A secondary.
Any suggestions as to which way would be beter to build ?
(1)-series all primaries , parallel all secondaries (after checking phase)
And use 1 rectifier.
OR
(2)-series all primaries , use a rectifier for each transformer , then paralell.

also should i fuse each transformer or will one fuse doo.

Just in the idea stage now.
Any assistance would be greatly appreciated

 

Paralleling secondaries is generally a really bad idea. You will get circulating currents.

 

It is possible if the transformers are of the same making.

If there are no sparks when you connect the wires, there is also no or only very little circulating current.

Alternatively, use two or more voltage regulators, and connect their outputs. Linear regulators can be connected in parallel without precaution. I have done it one time myself some years ago.

 

all transformers are identical,
so it shouldnt be an issue if i use a full wave rectifier for each transformer?

 

If you don't observe sparks when you connect the wires, there is no significant current flowing. Or you can test with an Amp meter as well.

 

Why are you putting the primaries in series? Is your AC supply 240VAC?

If your supply is 120VAC, then put the primaries in parallel as well. I'm assuming your reason for paralleling two transformers is to get 12V at 10A using two 5A transformers.

Regards,
Ifixit

 

yes my mistake i indeed intend to parallel the primaries.