How to lower the secondary voltage of a transformer

myfavoritething · 18th December 2006, 11:20 PM

Hello, I have a pb with a toroidal transformer which gives 45/0/45 V AC which is a bit higj for my UCD 400. 42 ou 43 V would be better. Is there any possibility to lower this voltage instead of a variac in the primary. I think to a post in a forum, but I am unable to find again. It was suggested to wind a external winding on the core (this I am sure) and connect it in reverse phase to lower secondary voltage (this is what I remerber, but here I ma not sure). I tried, but the wire was too thin and get very hot. Maybe some resistor should be put in series with the new winding to limit current ?
In general, what do you thing of this approach.
Of course, I can order again a new transformer, try to find the correct voltage and wait for x weeks to receive at worse an unusable transfo (last order before this one…).
Thank for reading me, I hope you could help me. Philippe

paulb · 18th December 2006, 11:37 PM

You can use the external winding, with a larger wire.
You can use a lower-voltage transformer with its secondary in series with the primary, out of phase, so that it bucks the input voltage.

mitwrong · 19th December 2006, 12:32 PM

Try to check if your transformer has 200, 220. and 240V ac input, then try to input from the highest 240v if your local supply voltage is lower than, or series a resistor to consume a bit from the primary source.

SUGGESTION IS FOR YOUR REFERENCE, IT MAY CAUSE YOUR CIRCUIT BETTER OR WORSE.

sss · 20th December 2006, 10:30 PM

adding resistors to the primary winding is a bad idea .
unwind a few turns from the secondary is the best option , but i guess u cant reach it .
if 2V is all u need , u can simply add 2-3 rectifeir diodes to the secondary , that better then using resistors.

18th December 2006, 11:20 PM	#1
myfavoritething diyAudio Member Join Date: Feb 2006 Location: Bretagne	How to lower the secondary voltage of a transformer Hello, I have a pb with a toroidal transformer which gives 45/0/45 V AC which is a bit higj for my UCD 400. 42 ou 43 V would be better. Is there any possibility to lower this voltage instead of a variac in the primary. I think to a post in a forum, but I am unable to find again. It was suggested to wind a external winding on the core (this I am sure) and connect it in reverse phase to lower secondary voltage (this is what I remerber, but here I ma not sure). I tried, but the wire was too thin and get very hot. Maybe some resistor should be put in series with the new winding to limit current ? In general, what do you thing of this approach. Of course, I can order again a new transformer, try to find the correct voltage and wait for x weeks to receive at worse an unusable transfo (last order before this one…). Thank for reading me, I hope you could help me. Philippe

20th December 2006, 10:30 PM	#4
sss diyAudio Member Join Date: Jul 2003 Location: Israel , haifa	adding resistors to the primary winding is a bad idea . unwind a few turns from the secondary is the best option , but i guess u cant reach it . if 2V is all u need , u can simply add 2-3 rectifeir diodes to the secondary , that better then using resistors. __________________ if you are not living on the edge you are taking too much space

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
help with transformer secondary voltage reading	jarthel	Parts	6	17th September 2006 11:48 PM
transformer specs such as DCR and etc: how does it affect voltage on the secondary?	jarthel	Parts	10	1st September 2006 02:18 PM
Secondary voltage for heaters	pengboon	Tubes / Valves	3	1st February 2006 02:09 PM
secondary voltage vs. primary voltage	Stocker	Parts	5	11th March 2004 07:41 PM

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

18th December 2006, 11:37 PM	#2
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	You can use the external winding, with a larger wire. You can use a lower-voltage transformer with its secondary in series with the primary, out of phase, so that it bucks the input voltage.

19th December 2006, 12:32 PM	#3
mitwrong diyAudio Member Join Date: Oct 2006	Try to check if your transformer has 200, 220. and 240V ac input, then try to input from the highest 240v if your local supply voltage is lower than, or series a resistor to consume a bit from the primary source. SUGGESTION IS FOR YOUR REFERENCE, IT MAY CAUSE YOUR CIRCUIT BETTER OR WORSE.

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