Power Transformer: 110V and 220V input, with two 15V outputs 180 degrees out of phase











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I have never designed a power supply before and have a few questions and would appreciate any help.




  • Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?


  • Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?


  • Lastly, I cannot find any transformers with these specifications. What I've been looking for is a center tap primary and secondary with a ratio of 15:1



Thank you in advance.










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  • 1




    Is that 15V AC or DC? And does it need to be isolated?
    – ratchet freak
    Nov 12 at 12:08








  • 1




    A centre tapped transformer CANNOT be rewired as you seem to be implying.
    – Andy aka
    Nov 12 at 12:34















up vote
6
down vote

favorite












I have never designed a power supply before and have a few questions and would appreciate any help.




  • Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?


  • Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?


  • Lastly, I cannot find any transformers with these specifications. What I've been looking for is a center tap primary and secondary with a ratio of 15:1



Thank you in advance.










share|improve this question









New contributor




Andre Faraday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 1




    Is that 15V AC or DC? And does it need to be isolated?
    – ratchet freak
    Nov 12 at 12:08








  • 1




    A centre tapped transformer CANNOT be rewired as you seem to be implying.
    – Andy aka
    Nov 12 at 12:34













up vote
6
down vote

favorite









up vote
6
down vote

favorite











I have never designed a power supply before and have a few questions and would appreciate any help.




  • Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?


  • Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?


  • Lastly, I cannot find any transformers with these specifications. What I've been looking for is a center tap primary and secondary with a ratio of 15:1



Thank you in advance.










share|improve this question









New contributor




Andre Faraday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











I have never designed a power supply before and have a few questions and would appreciate any help.




  • Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?


  • Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?


  • Lastly, I cannot find any transformers with these specifications. What I've been looking for is a center tap primary and secondary with a ratio of 15:1



Thank you in advance.







power transformer






share|improve this question









New contributor




Andre Faraday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question









New contributor




Andre Faraday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









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edited Nov 12 at 12:50









SamGibson

10.6k41537




10.6k41537






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Check out our Code of Conduct.









asked Nov 12 at 12:05









Andre Faraday

333




333




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Check out our Code of Conduct.





New contributor





Andre Faraday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Andre Faraday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.








  • 1




    Is that 15V AC or DC? And does it need to be isolated?
    – ratchet freak
    Nov 12 at 12:08








  • 1




    A centre tapped transformer CANNOT be rewired as you seem to be implying.
    – Andy aka
    Nov 12 at 12:34














  • 1




    Is that 15V AC or DC? And does it need to be isolated?
    – ratchet freak
    Nov 12 at 12:08








  • 1




    A centre tapped transformer CANNOT be rewired as you seem to be implying.
    – Andy aka
    Nov 12 at 12:34








1




1




Is that 15V AC or DC? And does it need to be isolated?
– ratchet freak
Nov 12 at 12:08






Is that 15V AC or DC? And does it need to be isolated?
– ratchet freak
Nov 12 at 12:08






1




1




A centre tapped transformer CANNOT be rewired as you seem to be implying.
– Andy aka
Nov 12 at 12:34




A centre tapped transformer CANNOT be rewired as you seem to be implying.
– Andy aka
Nov 12 at 12:34










2 Answers
2






active

oldest

votes

















up vote
8
down vote



accepted










Using a centre-tapped primary usually means that you de-rate the transformer to half power.



enter image description here



Figure 1. Series and parallel connections for split-winding transformer. Image source: Electro-Dan. The linked article discusses torroidal transformers but the principle is the same for standard transformers.



Instead, the common approach due to its flexibility is to use a transformer with two 110 V primaries and two equal secondaries. The primaries can then be wired in series for 220 V operation and parallel for 110 V. Similarly, the secondaries can be wired in parallel for high current or series for higher voltage. The series connection point is, in effect, the secondary centre-tap.



enter image description here



Figure 2. For switching primary voltage by the user you would add a voltage selector switch. Source: Modulus Amplification.






share|improve this answer





















  • Thank you very much! Helped a lot!
    – Andre Faraday
    Nov 12 at 14:16










  • The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
    – Harper
    Nov 12 at 19:20


















up vote
6
down vote














Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?




The normal approach is to use a transformer that has two identical primary windings, each rated for 110V and half the total transformer power. You put them in parallel for 110V operation and put them in series for 220V operation. This optimizes the amount of copper required.




Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?




If you ground the center tap, you can use the other two terminals to make separate +15V and -15V supplies. The fact that they are out of phase allows you to use full-wave rectification for both supplies.




Lastly, I cannot find any transformers with these specifications.




That would be a product recommendation, which is off-topic here.






share|improve this answer





















  • Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
    – rackandboneman
    Nov 12 at 19:43











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
8
down vote



accepted










Using a centre-tapped primary usually means that you de-rate the transformer to half power.



enter image description here



Figure 1. Series and parallel connections for split-winding transformer. Image source: Electro-Dan. The linked article discusses torroidal transformers but the principle is the same for standard transformers.



Instead, the common approach due to its flexibility is to use a transformer with two 110 V primaries and two equal secondaries. The primaries can then be wired in series for 220 V operation and parallel for 110 V. Similarly, the secondaries can be wired in parallel for high current or series for higher voltage. The series connection point is, in effect, the secondary centre-tap.



enter image description here



Figure 2. For switching primary voltage by the user you would add a voltage selector switch. Source: Modulus Amplification.






share|improve this answer





















  • Thank you very much! Helped a lot!
    – Andre Faraday
    Nov 12 at 14:16










  • The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
    – Harper
    Nov 12 at 19:20















up vote
8
down vote



accepted










Using a centre-tapped primary usually means that you de-rate the transformer to half power.



enter image description here



Figure 1. Series and parallel connections for split-winding transformer. Image source: Electro-Dan. The linked article discusses torroidal transformers but the principle is the same for standard transformers.



Instead, the common approach due to its flexibility is to use a transformer with two 110 V primaries and two equal secondaries. The primaries can then be wired in series for 220 V operation and parallel for 110 V. Similarly, the secondaries can be wired in parallel for high current or series for higher voltage. The series connection point is, in effect, the secondary centre-tap.



enter image description here



Figure 2. For switching primary voltage by the user you would add a voltage selector switch. Source: Modulus Amplification.






share|improve this answer





















  • Thank you very much! Helped a lot!
    – Andre Faraday
    Nov 12 at 14:16










  • The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
    – Harper
    Nov 12 at 19:20













up vote
8
down vote



accepted







up vote
8
down vote



accepted






Using a centre-tapped primary usually means that you de-rate the transformer to half power.



enter image description here



Figure 1. Series and parallel connections for split-winding transformer. Image source: Electro-Dan. The linked article discusses torroidal transformers but the principle is the same for standard transformers.



Instead, the common approach due to its flexibility is to use a transformer with two 110 V primaries and two equal secondaries. The primaries can then be wired in series for 220 V operation and parallel for 110 V. Similarly, the secondaries can be wired in parallel for high current or series for higher voltage. The series connection point is, in effect, the secondary centre-tap.



enter image description here



Figure 2. For switching primary voltage by the user you would add a voltage selector switch. Source: Modulus Amplification.






share|improve this answer












Using a centre-tapped primary usually means that you de-rate the transformer to half power.



enter image description here



Figure 1. Series and parallel connections for split-winding transformer. Image source: Electro-Dan. The linked article discusses torroidal transformers but the principle is the same for standard transformers.



Instead, the common approach due to its flexibility is to use a transformer with two 110 V primaries and two equal secondaries. The primaries can then be wired in series for 220 V operation and parallel for 110 V. Similarly, the secondaries can be wired in parallel for high current or series for higher voltage. The series connection point is, in effect, the secondary centre-tap.



enter image description here



Figure 2. For switching primary voltage by the user you would add a voltage selector switch. Source: Modulus Amplification.







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 12 at 12:33









Transistor

78.5k777171




78.5k777171












  • Thank you very much! Helped a lot!
    – Andre Faraday
    Nov 12 at 14:16










  • The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
    – Harper
    Nov 12 at 19:20


















  • Thank you very much! Helped a lot!
    – Andre Faraday
    Nov 12 at 14:16










  • The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
    – Harper
    Nov 12 at 19:20
















Thank you very much! Helped a lot!
– Andre Faraday
Nov 12 at 14:16




Thank you very much! Helped a lot!
– Andre Faraday
Nov 12 at 14:16












The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
– Harper
Nov 12 at 19:20




The yellow and blue is not a center tap, they are the ends of two windings. A center tap is continuous through the transformer and cannot be separated.
– Harper
Nov 12 at 19:20












up vote
6
down vote














Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?




The normal approach is to use a transformer that has two identical primary windings, each rated for 110V and half the total transformer power. You put them in parallel for 110V operation and put them in series for 220V operation. This optimizes the amount of copper required.




Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?




If you ground the center tap, you can use the other two terminals to make separate +15V and -15V supplies. The fact that they are out of phase allows you to use full-wave rectification for both supplies.




Lastly, I cannot find any transformers with these specifications.




That would be a product recommendation, which is off-topic here.






share|improve this answer





















  • Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
    – rackandboneman
    Nov 12 at 19:43















up vote
6
down vote














Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?




The normal approach is to use a transformer that has two identical primary windings, each rated for 110V and half the total transformer power. You put them in parallel for 110V operation and put them in series for 220V operation. This optimizes the amount of copper required.




Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?




If you ground the center tap, you can use the other two terminals to make separate +15V and -15V supplies. The fact that they are out of phase allows you to use full-wave rectification for both supplies.




Lastly, I cannot find any transformers with these specifications.




That would be a product recommendation, which is off-topic here.






share|improve this answer





















  • Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
    – rackandboneman
    Nov 12 at 19:43













up vote
6
down vote










up vote
6
down vote










Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?




The normal approach is to use a transformer that has two identical primary windings, each rated for 110V and half the total transformer power. You put them in parallel for 110V operation and put them in series for 220V operation. This optimizes the amount of copper required.




Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?




If you ground the center tap, you can use the other two terminals to make separate +15V and -15V supplies. The fact that they are out of phase allows you to use full-wave rectification for both supplies.




Lastly, I cannot find any transformers with these specifications.




That would be a product recommendation, which is off-topic here.






share|improve this answer













Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?




The normal approach is to use a transformer that has two identical primary windings, each rated for 110V and half the total transformer power. You put them in parallel for 110V operation and put them in series for 220V operation. This optimizes the amount of copper required.




Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?




If you ground the center tap, you can use the other two terminals to make separate +15V and -15V supplies. The fact that they are out of phase allows you to use full-wave rectification for both supplies.




Lastly, I cannot find any transformers with these specifications.




That would be a product recommendation, which is off-topic here.







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 12 at 12:34









Dave Tweed

115k9143253




115k9143253












  • Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
    – rackandboneman
    Nov 12 at 19:43


















  • Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
    – rackandboneman
    Nov 12 at 19:43
















Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
– rackandboneman
Nov 12 at 19:43




Yeah, and don't attempt to half-wave rectify them unless either your load is balanced or your transformer mount is very sturdy and well dampened :)
– rackandboneman
Nov 12 at 19:43










Andre Faraday is a new contributor. Be nice, and check out our Code of Conduct.










 

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