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In Reply to: RE: Can I connect the output of 2 identical transformer to get double power? posted by akltam on May 04, 2015 at 06:21:13
Yes, but you will need to make sure 100% they are in phase with one another. IF out of phase they will buck one another like two Bull Moose!*****You must observe polarity markings on the two transformers being paralleled.******
Just to be on the safe side wire the two primary windings of the two transformers in parallel, observing polarity markings.
Next connect one secondary lead of one transformer to one secondary lead of the other transformer observing polarity markings. Leave the other leads of the two transformer's secondary windings open. Do not tie, connect, them together.
Energize the primary of the two paralleled transformers.
Next check for voltage between the two unconnected secondary leads of the two transformers.
IF the two transformers are wired in phase with one another you should measure zero or near zero volts. Near zero volts, like maybe just a few volts.
IF you measure twice the nominal secondary voltage of each transformer then the two transformers are not in phase with one another. They are wired out of phase.
Example, if the secondary output voltage of each transformer is 120Vac nominal and you measure 240Vac nominal, the two transformers are not wired in phase with one another.
Edits: 05/04/15Follow Ups:
The power transformer I am talking about is a Lundahl LL1669A.This transformer has multiple different secondaries such as high voltage coil, 6.3V coil for the filament ...etc.
I have one of the LL1669A driving only 1 pair of 6550 tube. (no problem here). This amp is driving the tweeter in my active system.
I have the second LL1669A driving 2 pairs 6550 tube. The transformer gets very hot as it is approaching the limit VA of this transformer. This is driving the BASS in my active system.
I was thinking if I can connect the High voltage (340V) coil from first LL1669A transformer to the high voltage (340V) coil of the second transformer so that the first transformer can share the loading of the 2nd transformer.
Note that there are other coils like 6.3V for the filament of each transformer which were loaded different under each amp. And I am planning to leave those other coil untouch.
So to be short, I am planning to connect only the High voltage coil of the LL1669A together. As the other coils of the first transformer are loaded differently to the other coils of the second transformer. The total loading of the 2 transformers will still be different.
Do you think I can share the power of the High voltage coil this way between the 2 transformer.
Alan
Edits: 05/04/15 05/04/15
I was thinking if I can connect the High voltage (340V) coil from first LL1669A transformer to the high voltage (340V) coil of the second transformer so that the first transformer can share the loading of the 2nd transformer.
What is that going to do to the DC power supplies that you will also be tying together? I would not do what you are proposing.
Question is if the equipment was designed and manufactured for the transformer installed in the unit, why is it running hot? Is there something in the DC power supply drawing more current than it should? Is there something in the load connected to the DC power supply drawing more current than it should?
Is the AC Line voltage feeding the primary of the transformer higher than 10% of its'speced primary rating? That can cause a power transformer to run hotter than it should.
How about devices on the AC mains causing excessive odd harmonics on the mains? That can cause a power transformer to run hotter than it should.
Is the transformer well ventilated? Anything blocking airflow around the equipment and transformer/s?
Edits: 05/04/15 05/04/15
You should probably post these questions to Kevin Carter on the K&K Audio forum. Yes you can connect secondaries as long as you observe polarity (see Lundahl data sheets). Kevin will also tell you that you can run Lundahl power transformers hot until the cows come home without any problems. Kevin told me about a Lundahl transformer he ran for years so hot that the white label on top had turned brown with no issues.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
I agree with your scenario for being certain the two transformers are in parallel, but isn't there another issue? Each transformer will "see" the other as a load in parallel with the intended load, presumably a speaker.
I took it the OP was asking about AC power transformers and not output power transformers. My above response is for paralleling AC power transformers.
Edits: 05/04/15
I think you're correct, and I misunderstood what he wanted to do.
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