Discussion in 'The Projects Forum' started by mmswaid, Oct 15, 2013.

1. mmswaid Thread Starter New Member

Apr 1, 2012
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First of all I am sorry because English is not my mother language ,
I am working on a project related to pulsed dc transformers , I have a question & i hope somebody can help me to answer it and discus it ,
the question is If i wound a transformer which i will use as a pulsed dc transformer , lets assume 12 v 2 amps input to 6 v 4 amps output , if i wound double primaries with the same number of turns , one is fed by 12v ,2 amps pulsed dc , the other primary is fed by 10v 1 amps pulsed dc , what will i get in the secondary ??? what i need to know ( does the magnetic induction in the transformer core increase by using the second primary ? do i have to fix the voltage to 12 v to get the effect ? do i have to fix the current ??
please if someone can explain or have a reference , i would be thankful ,

2. wayneh Expert

Sep 9, 2010
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Are you planning for the two primaries to pulse in perfect phase with each other, or will they fight each other at times?

The field developed in the core by the windings depends on the current and the number of turns, not voltage.

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3. mmswaid Thread Starter New Member

Apr 1, 2012
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thank you for replying , the 2 primary coils will pulse at the same time in the same direction,in this case what i can expect please ?

Last edited: Oct 15, 2013
4. wayneh Expert

Sep 9, 2010
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I speculate (=guess without any analysis) that the effect will be additive to the emf developed in the secondary. ∑ of amp*turns.

5. mmswaid Thread Starter New Member

Apr 1, 2012
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so can you please guide me to a reference where i can check accurate formulas for this case ?

6. t_n_k AAC Fanatic!

Mar 6, 2009
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One would need more information to conduct an analysis of the problem.

Are the primary windings being fed with voltage or current sources? Presumably you would have voltage sources.....?

Identical (ideal) windings wouldn't have different voltages at their terminals - you couldn't have 12V on one primary winding and 10V on the other identical but isolated winding on a common core.

Can you provide a more complete summary of the circuit configuration you are trying to analyze? A schematic diagram always helps.

7. mmswaid Thread Starter New Member

Apr 1, 2012
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sorry i do not have schematic diagram now , but i have a 2 different power sources each connected to one of the primaries pulsed with 2 mosfets which is getting their pulse from one 555 timer , i know it is weird , but if this happens and the primaries are parallel & with the same number of turns , do you thing that will give more flux in the core , which means the output of the secondary will increase than using only one primary ?? and why i couldn't have 12V on one primary winding and 10V on the other identical but isolated winding on a common core. what will happen , how this configuration will affect the secondary output , thank you for following up with me .

8. t_n_k AAC Fanatic!

Mar 6, 2009
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Different voltages would be sustained at identical windings only if the currents differ such that the winding (&/or source) resistance voltage drops allowed for the same effective winding emf's. It's basic transformer theory. Identical windings on a common core sharing the same mutual flux will have identical emf's.

9. mmswaid Thread Starter New Member

Apr 1, 2012
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so what would you expect to happen in the secondary coil if i made this configuration ??

10. wayneh Expert

Sep 9, 2010
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Can you do the experiment and tell us?

11. crutschow Expert

Mar 14, 2008
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For identical windings the 12V pulse will generate a 12V pulse on the opposite winding. Thus, if the 10V source is low impedance, this will drive current backwards through the 10V source. If you wanted the current (not voltage) to add from the two sources then you would need the two windings to be wound with a relative turns ratio of 10/12.

Remember that all transformer winding voltages are determined by the common flux in the core and the maximum flux is determined by the highest applied voltage.

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12. mmswaid Thread Starter New Member

Apr 1, 2012
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so if i have 10 turns of the 10v supply+12 turns of the 12v supply ( on the primaries ) then i will get 6v on the 6 turns secondary ( which is the highest voltage of the 2 primaries ) but the current in the secondary would be higher whan ehat i wil get from using only 12v 12 turns primary, did i get it right ?

13. mmswaid Thread Starter New Member

Apr 1, 2012
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I will next week , we have a holiday for the next 5 days , i need some parts that i do not have , next week i will try & tell you , thank you for your interest .

14. crutschow Expert

Mar 14, 2008
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In theory. But an actual transformer will likely require more turns to avoid core saturation. The relative ratio of the windings will be 10:12:6 but in could actually be 50:60:30 turns. It depends upon the core saturation characteristics and the pulse width of the signal.

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15. mmswaid Thread Starter New Member

Apr 1, 2012
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that is right , i gave an example assuming the number of turns , but the actual number of turns will be calculated according to core cross section and power needed .

Last edited: Oct 16, 2013
16. mmswaid Thread Starter New Member

Apr 1, 2012
10
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I am sorry but to check that i got the idea right , If i have a transformer with 2 primary coils , the first is 12 turns fed by 12 v 2 amps , the second is 10 turns fed by 10 v 1 amps , the secondary is 6 turns , I should expect that the output of secondary will be 6v ( according to the ratio of turns between the higher voltage primary & the secondary 6/12*12 v of the primary ) and the secondary current will be approximately 34/6 amps ( 12 v X 2 amps + 10 v X 1 amps)/6 v
Is this accurate ? ( all number are just for example purpose )

Last edited: Oct 16, 2013