hi, i want to design a matching transformer. my question is how tapping a transformer works, if we have different resistances at its tappings ?? e.g: if we have 10 turns on primary side and 30 turns on secondary side. secondary side have tapping after each 10 turns and at each tapping are attached 10 Ohm resistance. so what is the resistance seen by primary side ? 
by m.ammar
November 26, 2018 
Can you please provide a circuit diagram? 
by mikerogerswsm
November 26, 2018 
by m.ammar
November 26, 2018 

Sorry, don't understand your circuit. What is connected to what? What is the total number of turns? (Shown both as 10+10 and as 30) 
by mikerogerswsm
November 26, 2018 
there are total 30 number of turns on secondary side. and after each 10 turns there is a tapping to which a resistor is connected. i just want to know what is the resistance seen by primary side.. Secondly, if you have any link regarding impedance transformation using tapping transformer kindly share it with me 
by m.ammar
November 27, 2018 
If you look at your circuit it is not possible. You have shorted out ten turns and the second ten turns goes to R2. There is no third ten turns. The resistors in your question were ten ohms and the resistors in your circuit are a hundred ohms each. The link you request can be worked out from ohms law, bearing in mind that the turns scale the voltage. Alternatively use google. 
by mikerogerswsm
November 27, 2018 
If this is what you intend: then the impedance reflected to the primary is: 10 // 2.5 // 1.11 ohms ignoring stray effects. 
ACCEPTED
+1 vote by mikerogerswsm November 27, 2018 
ps  This is easiest to think of in terms of energy. Each resistor dissipates V^2/R and so the reflected impedance must dissipate the sum of the energies. 
by mikerogerswsm
November 28, 2018 
pps  Doing this in one's head the primary reflected impedance is 10/14 or 0.7 ohms. 
by mikerogerswsm
November 28, 2018 
Thank you so much.. Kindly just tell me how you explain the resistances you calculated? i.e 10//2.5//1.11 
by m.ammar
November 28, 2018 
This is standard bookwork. It can be studied at college or in a textbook or on line. A really good student might reason it out from Ohm's Law. 
by mikerogerswsm
November 28, 2018 
Energy method: With input voltage V: power in R1 is V^2/R1 or V^2/10 power in R2 is (2V)^2/R2 or 4.V^2/10 power in R3 is (3V)^2/R3 or 9.V^2/10 total power = 14.V^2/10 = V^2/Rreflected therefore Rreflected = 10/14 = 0.714 ohms 
by mikerogerswsm
November 28, 2018 
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