power transformers in series

Jaap · 19th February 2006, 11:33 AM

If I put two transformers in series that each can deliver 100 mA, can I then take 200 mA from the pair ?

alex278 · 19th February 2006, 11:43 AM

Approximately, yes. However, if one of the tansformers delivers slightly less voltage than the other, or behaves differently when loaded, the other transformer will sink some current in the 'different' transformer. So I would be very careful.

(and remember that you'll need to have the phases of the windings correct, or otherwise you'll have an instant short-circuit)

Tweeker · 19th February 2006, 12:00 PM

Would you not get double the voltage, not double the current running them in series?

Perhaps you mean in parallel, where the above comments would apply?

jeapel · 19th February 2006, 12:05 PM

hi

200ma with 2 transfo = parallel not serie

and you need 2 exactly identical transfo

and double check phase like alex278 said

but maybe the best solution if you have

2 transfo would be 2 power supply with better channel

seperation for better stereo image

bye

Geek · 19th February 2006, 12:05 PM

Nope.

Series doubles voltages, not current. Actually, due to I²R losses, the current will probably be 0.95 times that of one unit (ref: Hammond data sheet)

Parallel doubles current while voltage remains the same.

Jaap · 19th February 2006, 12:31 PM

why I can fry an egg on the transformers. I will set them parallel and will a take another circuit to get the needed voltage (scottky diode + tube rectifier in a bridge, omitting the center tap).
Thanks guys !

jeapel · 19th February 2006, 12:45 PM

scottky diode ? are 40volt max. after it s a short circuit

but send a schematic to understand your design

but now turn off :-) your power supply because

transfo are very $$

Jaap · 19th February 2006, 12:50 PM

I will use BYW96e

jeapel · 19th February 2006, 04:28 PM

ok it s not a schottky diode but a 1000volt diode

test :

1-take just 1 transfo +BYW96E bridge +tube diode(for turn on
delay if i understand)
2-without load check temp after 1 hour (max. 40 to 50 C )
3-if ok try maybe 25ma after 50ma after 75ma to find the
max load for 1 transfo

Jaap · 19th February 2006, 07:23 PM

The circuit of the diodes is the same as in this attached file. It is a nice solution if you do not have a centertap on your transformer. I found this solution in a magazine that is about 50 years old and you can still use it for free

19th February 2006, 11:33 AM	#1
Jaap diyAudio Member Join Date: Dec 2002 Location: Netherlands	power transformers in series If I put two transformers in series that each can deliver 100 mA, can I then take 200 mA from the pair ?

19th February 2006, 12:00 PM	#3
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Would you not get double the voltage, not double the current running them in series? Perhaps you mean in parallel, where the above comments would apply? __________________ Be sure your foil hat has a good low impedance ground.

19th February 2006, 12:31 PM	#6
Jaap diyAudio Member Join Date: Dec 2002 Location: Netherlands	now I understand why I can fry an egg on the transformers. I will set them parallel and will a take another circuit to get the needed voltage (scottky diode + tube rectifier in a bridge, omitting the center tap). Thanks guys !

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19th February 2006, 11:43 AM	#2
alex278 diyAudio Member Join Date: Sep 2005	Approximately, yes. However, if one of the tansformers delivers slightly less voltage than the other, or behaves differently when loaded, the other transformer will sink some current in the 'different' transformer. So I would be very careful. (and remember that you'll need to have the phases of the windings correct, or otherwise you'll have an instant short-circuit)

19th February 2006, 12:05 PM	#4
jeapel diyAudio Member Join Date: Sep 2003 Location: quebec	hi 200ma with 2 transfo = parallel not serie and you need 2 exactly identical transfo and double check phase like alex278 said but maybe the best solution if you have 2 transfo would be 2 power supply with better channel seperation for better stereo image bye

19th February 2006, 12:05 PM	#5
Geek diyAudio Member Join Date: Sep 2004	Nope. Series doubles voltages, not current. Actually, due to I²R losses, the current will probably be 0.95 times that of one unit (ref: Hammond data sheet) Parallel doubles current while voltage remains the same.

19th February 2006, 12:45 PM	#7
jeapel diyAudio Member Join Date: Sep 2003 Location: quebec	scottky diode ? are 40volt max. after it s a short circuit but send a schematic to understand your design but now turn off :-) your power supply because transfo are very $$

19th February 2006, 12:50 PM	#8
Jaap diyAudio Member Join Date: Dec 2002 Location: Netherlands	I will use BYW96e

19th February 2006, 04:28 PM	#9
jeapel diyAudio Member Join Date: Sep 2003 Location: quebec	ok it s not a schottky diode but a 1000volt diode test : 1-take just 1 transfo +BYW96E bridge +tube diode(for turn on delay if i understand) 2-without load check temp after 1 hour (max. 40 to 50 C ) 3-if ok try maybe 25ma after 50ma after 75ma to find the max load for 1 transfo

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