Questions about transformer:

[nick]

1. Is primary current means that the current pass through the primary
coil or the current flow in the whole primary part ?

2. how to define the secondary current? Because of we have a formula

I1/I2=n2/n2

Then we can obtain I2(current of secondary part) current



Another formula is V1/V2=n1/n2

We also obtain V2 (voltage of secondary part)



The question is when I connect a load to the secondary part , the load is
R=1K ohm , should I use (V2)^2/R to define the current ,or use the formula
I1/I2=n2/n2

to define the current?
because the two answer is different



thanks!

 

[Joe McElvenney]

Hi,

It is difficult to understand exactly what it is that you want
but here goes. In an IDEAL TRANSFORMER -

Vp/Vs = Np/Ns = Is/Ip

so that while the primary and secondary voltages are in the
same ratio as the primary and secondary winding turns, the
currents are in their inverse. This is necessary because if the
secondary voltage is increased or decreased as a result of
transformer action, its current has to decrease or increase
accordingly so that no power is gained or lost.

So, if you know Vs and the secondary load is 1,000 ohms, then
the secondary current is Vs/1000 Amps.

From the relationship above, the current flowing into and
out of the primary (not into the secondary as well, as you
appear to be asking) is -

Ip = Vs/1000 x Ns/Np Amps.


I hope this helps.


Cheers - Joe

 

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The question is when I connect a load to the secondary part , the load is
R=1K ohm , should I use (V2)^2/R to define the current ,or use the formula
I1/I2=n2/n2

to define the current?
because the two answer is different

thanks!

The secondary current is I2 = V2/R (V2 is not squared).
Also, I1/I2 = n2/n1 (not n2/n2 -- typo error?)

Mark