Wiring Transformers in Series With a 240V Plug From a Generator?

Question

How should I wire 2 transformers in series (either primaries or secondaries)(not sure which I should use) using a NEMA L14-30 plug from a generator socket? I'm using 2 Microwave Oven Transformers to make a homemade stick welder. I was thinking about using a shared neutral for both.

Questions:

1)Is this a good configuration? (Generator/Shared Neutral)

2)If it is, should I wire the primaries or secondaries in series, and what advantages (or much more likely disadvantages) will be involved in either choice?

3) Can you show/describe the best (or at least a recommended) approach for doing this off of this type of plug?

Answer 1

if they're 120v transformers (and seeing as you've got a NEMA connecter there they probably are) connect them in series,

and connect the neutral to equalise the voltage if there's a mis-match between the two transformers, also wire the secondaries in series. secondaries in parallel could cause circulating currents if the transformer ratios don't match.

Answer 2

If you have microwave oven transformers that are rated 120 volts and a generator with 120/240 volts, then it makes sense to connect one primary winding to one of the two hot terminals and the other to the second hot terminal and both windings to the neutral. That will load both sides of the transformer rather that putting all of the load on one side.

You will need to replace the high-voltage secondary winding of each transformer with a low-voltage winding that you wind according to instructions that you find on the internet. You can connect the two secondary windings in parallel. This scheme will provide twice the current you would have by using just one transformer.

That being said, asking this question here indicates that you are not very well qualified to undertake this project. You can not expect to learn enough here to do this safely. You should study some more about basic electrical circuits, transformers etc. You should also look at as many plans for microwave oven transformer projects as you can find and make sure that you understand them.

After looking at another answer that you have. I agree that connecting the secondaries in parallel is better. Double the size of the secondary wire compared to what is recommended for a welder using a single transformer and use half as many turns. That will give you the current increase with series windings.

Answer 3

hope I can be helpfull

First observation: either the transformers is wired in series or paralel, both pimary and secondary have to be wired!

Second observation: if you shared neutral of the transformers, then the only configuration is paralel (seies don´t share neutrals nor fase)

1) The best configuration depends on your needs. 2)Series configuration: Same current, double voltage. Paralel configuration: Same voltage, double current.

All this is assuming that both transformer are exactly the same. If not, for paralel configuration you need to check that the primary and secondary voltages need to bee the same as well also the shortcircuit voltage. If not, there will be current flowing between the transformers.

Warning: I agree with Charles Cowie, it may be dangerous to work with this if you are not qualified.