Connecting 2 isolation transformers to double the current capacity

[FPALB]

I have 2 of these DALE TECHNOLOGY medical grade transformers, but they are only 3.5 amps each. Can I make a male to male 120V cable and jumper their secondary outlets to double the current capacity?

Only 1 of the outlets shown has a green dot on it, but Ive confirmed they are in parallel as a normal outlet would be.

 

[Speedskater]

If you have an old AC output wall-wort on hand.
You can test the transformers with a low voltage AC input.

 

[FPALB]

If you have an old AC output wall-wort on hand.
You can test the transformers with a low voltage AC input.

Good idea - I can do it with a Variac

 

[emrr]

At best you would have to assume one has barely lower wire resistance and will always draw some % more of the total load. In fact the wire resistance of your jumper and of the connectors may dictate the unit most directly plugged with respect to load with draw the most.

 

[JohnRoberts]

A 120VAC male to male cable is a shock hazard and possible house fire waiting to happen... An old neighbor of mine (now RIP) had an extension cord wired up with two male ends to provide power to his shed when the existing underground power line failed. This was wrong for several reasons, but I was unable to stop him from doing it.

-To parallel two iso-transformers the first consideration is to make sure the windings being combined are in the same polarity. Connecting them opposite polarity will end badly.

-confirm that they are making the same voltage output. If one is higher or lower than the other they will try to drive into each other.

-for modest current needs you can force sharing using degeneration resistors not unlike the emitter resistors inside power amps to force device sharing. A 0.1 Ohm resistor would drop 0.35 V @ 3.5A

Have fun and be careful, even with iso-transformers mains voltage can still kill you.

JR

 

[Rob Flinn]

Just a thought, but could you not just power different bits of gear from each of the 2 different transformers ? Is it essential that everything is being powered from the pair of transformers in parallel on the same circuit ?