Hello guys have a little problem see if anyone can help Q the primary winding re

Question

Hello guys have a little problem

see if anyone can help

Q the primary winding resistance is 125Ohms, Secondary is0.7ohms calulate the transformers copper loss at full load.

now the transformers name plate is 240V 50Hz 28VA theearlier question explains it is a step down transformer delivering12V

so primary Current = Vp/Rp 240/125 = 1.92A

now im not sure what figures to use to calc the current insecondary winding at full load

i get values from 40A to 38.4A down to .116A

using formula Full load current = VA rating/primary voltage iget .116A

i need Is value for copper loss formula

Copper loss W= Ip(sq)xRp+Is(sq)+Rs

any help appreciated

Explanation / Answer

Given :          Resistance of primary coil (Rp) = 125          Resistance of secondary coil (Rs) = 0.70           and   Vp   =   240 V                  Ip   =   Vp /Rp                             = 240 / 125                           =   1.92   A Input Power is :                Pin      =   Vp *   Ip                           = 240 V * (1.92 A)                           =   460.8   W    Here     Pin     =   Pout       But   Pout    = Is2 R      or      Is       =  [   Pout   /Rs ] 1/2                          =   [  460.8   / ( 0.70 ) ] 1/2                          =  25.66 A Copper Loss is :        W  =       Is2   Rs + Ip2 Rp             =     (25.66 )2 * 0.70    +   (460.8 )2 * 125             =   ----------   Calculate it . Hope this helps u!

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