quick question about 240 to 220 volts transformer.

marchel · 15th August 2009, 03:13 PM

Dear diy friends,

I want to buy a 80va toroidal transformer, but the problem is, it has 240volts input primary and our local voltage is 220volts. Will it be ok? what is the disadvantage of this setup?

thanks.

peranders · 15th August 2009, 03:37 PM

Indeed!

The disadvantage is possibly a bit heavier transformer than necessary but nowadys much electric gear (in Europe at least) is designed for 220-240 VAC.

Stu · 15th August 2009, 03:40 PM

Shouldn't be a problem at all.

The only disadvantage is that the maximum power you can get out of it will be very slightly less. Not enough to worry about, anyway.

marchel · 15th August 2009, 03:43 PM

Thank a lot ,

The transformer will be feeding a regulator for a Pass class A preamp, So the power loss is practically none issue...I guess.

Thanks.

Akita · 15th August 2009, 03:44 PM

It should be fine.

Incoming ac supply may fluctuate sometime. To avoid it, you may need a regulated supply.

The ratio of your trans difference for 240 and 220. Let say, secondary is 12v then

1)12/240= 0.05 ;
2)12/220 = 0.0545 ;

If the supply for the trans no.2 is 240vac then the secondary will be 240 x 0.0545 = 13v

marchel · 15th August 2009, 03:57 PM

My regulator needs 18V AC to produce a 15V DC , Do you think there is still enough headroom for the regulator to regulate, When you factor the slight voltage drop, Due to the primary mismatch? If I buy a transfo. with 240V pri./ 18-0-18 secondary plugged into a 220 outlet?

Thanks.

Spiny · 15th August 2009, 05:17 PM

At 220v in will give 16.5 - 0 - 16.5, that might just save your regulator, rectified the 16.5vAC will give 23V peak instead of 25.5V a saving of 2.5watts dissapation per amp drawn from the regulator.

Bit simplistic and others will do the full maths with transformer regulation and diode drop taken into account - It will do

You have measured your AC line voltage I take it? As the 220V is nominal in europe, and can vary quite a bit - also depends on how near the substation you are and how heavy are the other loads on the substation are. Carefull measuring it though - it can bite

AudioFreak · 15th August 2009, 06:54 PM

Worst case is likely be to approximately

(18*(220/240)*0.9*0.9*1.4)-2 = 16.7V DC so it may not always be able to provide 18V DC for the regulator input.

If the transformer is only lightly loaded then the voltage will likely be somewhat higher.

wwenze · 15th August 2009, 11:46 PM

Heh... people in my country have it the other way round, trying to use 230-240V supply with 220V China products.

Not much hiccups. Maybe the regulators run hotter.

15th August 2009, 03:13 PM	#1
marchel diyAudio Member Join Date: Nov 2007	quick question about 240 to 220 volts transformer. Dear diy friends, I want to buy a 80va toroidal transformer, but the problem is, it has 240volts input primary and our local voltage is 220volts. Will it be ok? what is the disadvantage of this setup? thanks.

15th August 2009, 03:37 PM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Indeed! The disadvantage is possibly a bit heavier transformer than necessary but nowadys much electric gear (in Europe at least) is designed for 220-240 VAC. __________________ /Per-Anders (my first name) or P-A as my friends call me

15th August 2009, 06:54 PM	#8
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	Worst case is likely be to approximately (18(220/240)0.90.91.4)-2 = 16.7V DC so it may not always be able to provide 18V DC for the regulator input. If the transformer is only lightly loaded then the voltage will likely be somewhat higher. __________________ - Dan

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15th August 2009, 03:40 PM	#3
Stu diyAudio Member Join Date: May 2003 Location: Wollongong	Shouldn't be a problem at all. The only disadvantage is that the maximum power you can get out of it will be very slightly less. Not enough to worry about, anyway.

15th August 2009, 03:43 PM	#4
marchel diyAudio Member Join Date: Nov 2007	Thank a lot , The transformer will be feeding a regulator for a Pass class A preamp, So the power loss is practically none issue...I guess. Thanks.

15th August 2009, 03:44 PM	#5
Akita diyAudio Member Join Date: Dec 2006 Location: Kuala Lumpur	It should be fine. Incoming ac supply may fluctuate sometime. To avoid it, you may need a regulated supply. The ratio of your trans difference for 240 and 220. Let say, secondary is 12v then 1)12/240= 0.05 ; 2)12/220 = 0.0545 ; If the supply for the trans no.2 is 240vac then the secondary will be 240 x 0.0545 = 13v

15th August 2009, 03:57 PM	#6
marchel diyAudio Member Join Date: Nov 2007	My regulator needs 18V AC to produce a 15V DC , Do you think there is still enough headroom for the regulator to regulate, When you factor the slight voltage drop, Due to the primary mismatch? If I buy a transfo. with 240V pri./ 18-0-18 secondary plugged into a 220 outlet? Thanks.

15th August 2009, 05:17 PM	#7
Spiny diyAudio Member Join Date: Feb 2008	At 220v in will give 16.5 - 0 - 16.5, that might just save your regulator, rectified the 16.5vAC will give 23V peak instead of 25.5V a saving of 2.5watts dissapation per amp drawn from the regulator. Bit simplistic and others will do the full maths with transformer regulation and diode drop taken into account - It will do You have measured your AC line voltage I take it? As the 220V is nominal in europe, and can vary quite a bit - also depends on how near the substation you are and how heavy are the other loads on the substation are. Carefull measuring it though - it can bite

15th August 2009, 11:46 PM	#9
wwenze diyAudio Member Join Date: Mar 2008	Heh... people in my country have it the other way round, trying to use 230-240V supply with 220V China products. Not much hiccups. Maybe the regulators run hotter.

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