PSU transformer question

kyrochan · 23rd March 2005, 09:51 PM

If I connect in parallel (matching together the 0V and the 24V wires) the secondaries of two identical trasformers rated for 24V/96VA should I obtain a 192 VA /24V trasformer?

audiofan · 23rd March 2005, 11:11 PM

yes you should, but remember that the primary and the secondary must be in phase, to make test always use a ligtbulb in series with the mains for your test if connection is ok the lightbulb will not ligt up if your connection is out of phase (reversed ) the light will go bright

kyrochan · 23rd March 2005, 11:45 PM

So, you say that it's possible that the colours of the primaries on the two transformer could be inverted?!
(my transformers is single primary / single secondary)
and so could happend that in the moment I matched the wires of the secoundaries (live with live and ground with ground) they could go in short?
Ehi, this is extremely dangerous!
What kind of mad engineer can make a mistake like this? !
..

Giaime · 24th March 2005, 06:58 AM

Ciao! Yes it can happen. But it is a rare event. Try the lightbulb trick in series with the primary leads. It senses the short and protect the transformers in case of serious trouble. In general if the 2 transformers are identical, just connect togheter the wires of the same color...

But why are you doing this? Get a cheap 225VA toroid and you'll thank yourself later... (I assume you are talking about EI transformers)

kyrochan · 24th March 2005, 09:13 AM

I've bought these 4 trasformers for just 15€, they are preatty heavy and well made, I bought 4 trasformers to create a two-rails psu like ones suggested by dejan Vaselinovich in his tnt articules...but since I search a pure class A amp, I 've decided to built a Zen amp (single ended) I think that I can't use a two rail psu in a single ended amp so I've decided to connct them parallel to got a nice psu for a 15-20W final mono.
If you could suggest a way to implement a two rail psu in S.E. amp make me know.
Cheers,
Domenico

K-amps · 24th March 2005, 10:53 AM

Guys,

Unless the trafo's are made to very high tolerances, they may not match. You need to connect all wires in paralell, then open one connection at one end of the secondaries and measure the voltage difference. It should be less than 0.05v (5mV) anything more and your transformer will drive the other and cook it.... use a 20-40 watt bulb to check.

SkinnyBoy · 24th March 2005, 10:56 AM

if we're talking seperate transformers, then I would parallel them after the bridge rectifiers

K-amps · 24th March 2005, 11:22 AM

If they are not matched to within 0.05v or so, then yes the next step would be to join after the Bridges.... but then you need an extra bridge.

kyrochan · 24th March 2005, 11:47 AM

Mmmmh, how did you think about this way to use the rectifiers???

K-amps · 24th March 2005, 11:53 AM

That gives you double the voltage and single supply.... is that what you wanted?

23rd March 2005, 09:51 PM	#1
kyrochan diyAudio Member Join Date: Jan 2005 Location: Bari	PSU transformer question If I connect in parallel (matching together the 0V and the 24V wires) the secondaries of two identical trasformers rated for 24V/96VA should I obtain a 192 VA /24V trasformer?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Transformer question?	mcameron	Parts	5	23rd January 2005 07:52 PM
transformer question	xcortes	Chip Amps	0	31st October 2004 05:04 AM
Transformer Question	TunaFish	Tubes / Valves	15	18th June 2004 11:20 PM
Transformer Question	toque_101	Chip Amps	2	26th January 2004 05:21 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

23rd March 2005, 11:11 PM	#2
audiofan diyAudio Member Join Date: May 2003 Location: quebec	yes you should, but remember that the primary and the secondary must be in phase, to make test always use a ligtbulb in series with the mains for your test if connection is ok the lightbulb will not ligt up if your connection is out of phase (reversed ) the light will go bright

23rd March 2005, 11:45 PM	#3
kyrochan diyAudio Member Join Date: Jan 2005 Location: Bari	So, you say that it's possible that the colours of the primaries on the two transformer could be inverted?! (my transformers is single primary / single secondary) and so could happend that in the moment I matched the wires of the secoundaries (live with live and ground with ground) they could go in short? Ehi, this is extremely dangerous! What kind of mad engineer can make a mistake like this? ! ..

24th March 2005, 06:58 AM	#4
Giaime diyAudio Member Join Date: Oct 2004	Ciao! Yes it can happen. But it is a rare event. Try the lightbulb trick in series with the primary leads. It senses the short and protect the transformers in case of serious trouble. In general if the 2 transformers are identical, just connect togheter the wires of the same color... But why are you doing this? Get a cheap 225VA toroid and you'll thank yourself later... (I assume you are talking about EI transformers)

24th March 2005, 09:13 AM	#5
kyrochan diyAudio Member Join Date: Jan 2005 Location: Bari	I've bought these 4 trasformers for just 15€, they are preatty heavy and well made, I bought 4 trasformers to create a two-rails psu like ones suggested by dejan Vaselinovich in his tnt articules...but since I search a pure class A amp, I 've decided to built a Zen amp (single ended) I think that I can't use a two rail psu in a single ended amp so I've decided to connct them parallel to got a nice psu for a 15-20W final mono. If you could suggest a way to implement a two rail psu in S.E. amp make me know. Cheers, Domenico

24th March 2005, 10:53 AM	#6
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	Guys, Unless the trafo's are made to very high tolerances, they may not match. You need to connect all wires in paralell, then open one connection at one end of the secondaries and measure the voltage difference. It should be less than 0.05v (5mV) anything more and your transformer will drive the other and cook it.... use a 20-40 watt bulb to check.

24th March 2005, 10:56 AM	#7
SkinnyBoy Banned Join Date: Nov 2002 Location: Adelaide, Australia	if we're talking seperate transformers, then I would parallel them after the bridge rectifiers

24th March 2005, 11:22 AM	#8
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	If they are not matched to within 0.05v or so, then yes the next step would be to join after the Bridges.... but then you need an extra bridge.

24th March 2005, 11:53 AM	#10
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	That gives you double the voltage and single supply.... is that what you wanted?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)