Transformer Question

Only if their characteristics are equal to each other.

Thanks for your reply.

But they are different, so what magnetizing current will pass through each ?

is it the smaller one?

How would I or anyone else ever know, unless you spell out a few details?

the difference in core material is not as important as the number of turns in each primary and the gauge of the wire of which it is composed. AND since you are hooking them accross an AC source at 60Hz, many things begin to become important. The self inductance of the individual primaries, and even a small amount of capacitance between the coils. These produce an effect known as reactance, which changes as the frequency changes. For a beginner look up Transformer in Wikipedia, it has a very clear explaination( and you should read all the sidebars). I used to build tesla coils, but that is another story.

Let's not forget the unspecified eddy currents that will be induced in presumably at least one of the two core material. Transformer design is not as simple as it looks.

The answer is they absolutely will not have 60 V on each primary. What the actual number is depends on the open secondary impedance of the primary. But, you've already said those were not the same.

But what about the magnetizing current which must be the same-how its value can be determined ?

The current that flows through the primaries will be the same, but not all of that is magnetizing current. You cannot, and will not, get a simple answer to a very complicated question.

Have you tried equivalent circuit analysis?

If nothing else, the OP could hook up the transformers in series, and simply tell us how the voltage divides between each (assuming he/she has a voltmeter and knows how to use it.)

Making measurements is quite easy, but we want to analyse the circuit and investigate why we got such measured values.

Okay, the measurements are easy. So why have you not told anyone what the measurements are?

Output open is a pure inductance (no back emf)

Two inductances in series. The voltage drop will follow KVL for AC circuits.

Based on the no-load currents (at the rated voltage) - as the simplest measure you can have equivalent (primary side) circuit of each transformer. Then apply KVL.

Two cases:first, no ideal case:both transformers must be treated as common impedances a finite inductive reactance plus some a little ohmic resistance each one,and is a basic AC circuit;second, ideal case:the reflected impedance on both primaries are infinite and not any current at all to produce any drop.This last case is very different to DC current :when you connect series two capacitors c1,c2, currents becomes zero but potencial drop given by c1.v1=c2.v2 .-

You complicate matters for no reason! Just express yourself clearly and try to understand the simple question....

Don't git yer knickers in a knot. Ferquiza has the right idea. The question is NOT simple. The primary current will always have a phase angle other than 0° or -90°.

That sounds like a homework or lab question from an impolite student. I think that he got more help than he deserves. He doesn't get it anyway.

Quite true and a GA.

If the transformers have identical primary windings and the only difference is the magnetic core material, then the voltage will divide equally. Just knowing that both transformer primaries are rated at the same voltage, does not insure that they have the same impedance. It is the primary impedance that determines how the voltage will be divided.

Identical primary windings (number of turns and wire gage) with different magnetic material are likely to have different magnetizing inductances. This means that the voltage will not divide equally. The exact value depends on the respective magnetizing inductances.

I think welderman answered what you need to know.

By the way as for the whole magnetizing current, you should try obtaining the equivalent circuit of each transformer and using KVL, I think you will get a really low magnetizing current (even lower than the original magnetizing current for each transformer) , with a phase angle really close to 90 degrees.

Could you please explain what is "KVL" ?

Kirchhoff's voltage law

Well, i think i got the answer for the first part of the homework, and the mains supply voltage will be divided according to the individual inductances as Kirchoff's law says.

Now let us go to the second part of the homework:

Each primary winding will have different voltage across it, and the magnetizing current shape for each winding will be determined from the B-H characteristics of each of the of the different magnetic materials.

How the "shape" of common current which passes through both will be determined ?

Please i need to have the answer before the due date which is the coming Friday.

Do your own homework!!!