transformer inductance 16000H??

[komalbarun]

Am a bit confused...

20:1 step down transformer, 240V to 12V @ 0.3 A 3.6VA.

what is the indcutor's primary coil's and secondary coil's inductance?

I get 16000H for primary and 40H for secondary coil !!?

pls help..I think my calculus is wrong or maybe it's my concept about the transformer itself which is wrong xD

 

[BobK]

16000H sounds a little high. How did you measure it?

The ratio is correct though: the square of the ratio of the windings.

Bob

 

[komalbarun]

well...
V = -L I ?

Pin = Pout, so ,
240V x I = 3.6VA
I = 3.6/240 V = 0.015A

240 = -L 0.015
-L = 240/0.015 = 16000

am I making a mistake somewhere?

 

[duke37]

Not V = I * L but V = I * Xl

Xl = 2*pi*F*L

You are too high by a factor of about 300.

 

[komalbarun]

Not V = I * L but V = I * Xl

Xl = 2*pi*F*L

You are too high by a factor of about 300.

how do I calculate the Xl if I don't know the L or vice-versa?

how do I use 12V @ 0,3A 3.6 VA to calculate the L (if possible)?

 

[duke37]

You measured Xl NOT L as I pointed out in the first equation.

Transposing the second equation (can you do this?)

L = Xl/(2*pi*F)

The 0.3A is the maximum current that the transformer can provide in the load without getting too hot or dropping too much voltage. It has nothing to do with inductance.

 

[Raven Luni]

Is it just me or are transformers much easier to understand than plain inductors?

 

[komalbarun]

You measured Xl NOT L as I pointed out in the first equation.

Transposing the second equation (can you do this?)

L = Xl/(2*pi*F)

The 0.3A is the maximum current that the transformer can provide in the load without getting too hot or dropping too much voltage. It has nothing to do with inductance.

thnx for that, its good to know

 

[komalbarun]

Not V = I * L but V = I * Xl

Xl = 2*pi*F*L

You are too high by a factor of about 300.

lol I just understood what you meant by this xD, so if am understanding right :

16000 = 2 * pi * f * L?

16000 = 2 * pi * 50 * L

L = 16000/ approx. 314
L = 50H ?

 

[duke37]

That looks right to me.

Raven
A simple transformer is relatively easy to understand but as soon as non linear effects or energy transfers are included, my mind boggles. Inductors can be used in so many ways.