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## Re: [Amps] Transformers in series

 To: "W2RU - Bud Hippisley" , Re: [Amps] Transformers in series "k7rdx" Sun, 12 Mar 2006 07:48:54 -0800
 ```And if unsure about phasing always bring the voltage up slowly with a variac while monitoring the secondary voltage. If the phasing is correct output will show with a small value of input...Jim.. ----- Original Message ----- From: "W2RU - Bud Hippisley" To: Sent: Saturday, March 11, 2006 7:56 PM Subject: Re: [Amps] Transformers in series > Rex Lint wrote: > > Be careful tho, the primaries and the secondaries BOTH have to be in > > parallel... or else you're just running a short circuit! > > > > I'm not sure Rex said exactly what he meant to say. > > You can put primaries in series and secondaries in parallel, or vice > versa, depending on what voltages in and out you're trying to accomplish > with the transformers you have on hand. What you CAN'T do with > paralleled secondaries is parallel them with their voltage waveforms OUT > OF PHASE. > > Examples: I have two filament transformers, 6.3 VAC @ 1 Amp secondary , > 115 VAC primary. If my input line voltage is 115 VAC, I would parallel > the primaries, and then I could either parallel the secondaries with > correct phasing to get 6.3 VAC @ 2 Amps, or I could put the secondaries > in series with correct phasing to get 12.6 VAC @ 1 Amp. Alternatively, > if my supply line was 230 VAC, I'd put the primaries in series and then > do either series or parallel secondaries, as before, depending on > whether I needed 6.3 VAC @ 2 Amp or 12.6 VAC @ 1 Amp. > > The problem is the PHASING. It is a bigger problem for paralleled > secondaries than for the series case. If I wire the two secondaries in > series out of phase, the only problem I have is my net secondary output > voltage will be zero or very close to zero. But with paralleled > secondaries, I have two voltage sources of opposite polarity trying to > feed each other; instead of seeing the rated load resistance, each > transformer will see very nearly a short circuit and catastrophe will > result. > > If you're lucky, the two transformers are identical and the leads coming > out of them are identically placed so that you can reasonably assume > which leads need to be tied together for proper in-phase operation. If > they're not identical, I use a scope or a small amperage fast blow fuse > in the primary to help me figure it out. I'm sure there are other, > cleverer techniques out there. > > Bud, W2RU > _______________________________________________ > Amps mailing list > Amps@contesting.com > http://lists.contesting.com/mailman/listinfo/amps _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ```
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