parallel secondaries

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parallel secondaries

Postby jetpack » Mon Jun 15, 2015 5:46 pm

Are there any problems associated with paralleling three independent secondaries rated at 0-6.3 (2A), 0-6.3 (2A), and 3.15-0-3.15 (2A) to get a single 0-6.3 (6A) supply? Would I just cap the center-tap and treat it like the other 0-6.3 windings?
Thanks!
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Re: parallel secondaries

Postby DeathRex » Mon Jun 15, 2015 6:05 pm

Sounds fine to me, just make sure you get the polarity correct, dim bulb tester would be great here. You should be able to use the center tap to either ground or put a DC voltage on.
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Re: parallel secondaries

Postby Gingertube » Mon Jun 15, 2015 9:57 pm

You could still use the Centre Tap. That would just make the whole thing a 3.15V-0-3.15V balanced supply.
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Re: parallel secondaries

Postby jetpack » Tue Jun 16, 2015 3:42 pm

Thanks for all the input. I'll forge ahead with the plan.
Cheers.
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Re: parallel secondaries

Postby dcriner » Sun Jun 21, 2015 9:08 am

I think this probably should be OK, but if the impedances of the windings are different, you may wind up with circulating currents when the parallel xfmr bank is unloaded.
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Re: parallel secondaries

Postby jetpack » Sun Jun 21, 2015 10:18 pm

Thanks for the comment dcriner. That is actually what I was worried about, but I'm not certain what the implications are.
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Re: parallel secondaries

Postby dcriner » Mon Jun 22, 2015 12:26 pm

If the xfmr doesn't get warm to the touch (with primary energized but no load on the paralleled secondaries), then I think it's OK. You can measure each winding with an ammeter to check for circulating currents. You can check the temperature rise of each winding by comparing the resistance with the primary disconnected and connected, allowing time for the temperature to reach steady-state. Look up the thermal coefficient of resistance rise for copper.
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