Connecting transformers in parallel question - Page 1
Forum section: electronics / beginners

author: temet
author_rank: Newbie
timestamp: March 30, 2013, 07:09:59 pm
content: I am abeginner,just trying to build my first proper project, a power supply for learning purposes. It will be a simple design with a couple of fixed output voltages. I have a couple of transformers that I got for buttons, from a market stall bin.I was thinking about connecting them in parallel to give me more amps on the output. I know the transformers to work like this are supposed to be the same spec. These two are very close, but vary slightly. Both are 24 volts and 50Hz, physically they are almost identical, but one is 30VA Max and the other is 36VA Max.What I'm asking is, will this work in practice?

author: Nickk2057
author_rank: Regular Contributor
timestamp: March 30, 2013, 10:50:16 pm
content: not really.. the only thing that will happen is when you hook em up in the wrong polarity it will short out... or it will fizzle out and die... its kinda tricky to check which way the phase on that will be going.. meaning that of the waves that goes aound the transformer... and with the higher VA on them it might put higher load on the lower transformer and make it rise up on that.. making it get hot and die out faster.. just be sure that the voltage is the same and the amps as well...Nickk2057

author: kxenos
author_rank: Frequent Contributor
timestamp: March 30, 2013, 11:39:25 pm
content: As this is for experimenting-testing purposes and has nothing to do with production, you can absolutely go for it. Nothing bad will happen. But as Nick meant, it's not a solution to be used permanently. But for testing-playing purposes IMO it's adequate.

author: digsys
author_rank: Unknown
timestamp: March 31, 2013, 12:10:13 am
content: MANY Transformers are supplied as dual output, so they can be wired in Series or Parallel. It's VERY common.Notes: You DO have to make sure the Phases are the SAME !! If you don't have a CRO then - connect 1 pair, temporary connecta series resistor with each second pair (current limiting of say 50-100mA), and tie the other end of the resistor together.With an AC multimeter, you'll either have Full AC or close to Zero ! in which case, swap the windings.Parallel can tolerate a small Voltage difference, say 0.5V in 15VAC. One winding may get a little warmer if you push it.That's about all. If the difference is a bit higher, just wash off some "output mismatch" by putting say a 1ohm power resistorin series with the higher winding. Calculate the AC difference, how many Volts to wash off at max current.You could put in 2 Bridges and join them up on the DC side, but that's a bit harder to get them to share, but not impossible.

author: David_AVD
author_rank: Super Contributor
timestamp: March 31, 2013, 12:40:00 am
content: I find the easiest way to determine phase on two secondaries is to simple hook them in series and measure the voltage across the outer wires.If the overall voltage is the sum of the secondaries, they are currently connected Start1-Finish1-Start2-Finish2.If the overall voltage is the one minus the other, they are currently connected Start1-Finish1-Finish2-Start2.

author: digsys
author_rank: Unknown
timestamp: March 31, 2013, 01:29:32 am
content: Quote from: David_AVDI KNEW there was an easier way, one of those senior moments :-) .. last time I trust my brain to fetch me Information !

author: notsob
author_rank: Frequent Contributor
timestamp: March 31, 2013, 02:32:04 am
content: This method is also used to determine unknown winding connections in 3-phase motors. ie excite 1 winding and connect the other two in series and measure the output