The operation of magnetically coupled circuits

• Engineering

Homework Statement

A transformer has 600 primary turns and 150 secondary turns. The primary and the second resistances are 0.25Ω and 0.01 Ω respectively and the corresponding reactances are 1.0Ω and 0.04Ω respectively.
Detemine the equivalent:
1. resistance
2. the reactance and
3. the equivalent impedance reffered to the primary winding
4. the phase angle of the impedance.

Anyone could help me with this question? Thank you

The Attempt at a Solution

I have been trying to answer some of them myself.
For equivalent resistance:
2
Re= R1 + R2= R1 + R2 ( V1 : V2)

Re= 0.41Ω

For equivalent reactance:
2
Xe= X1 + X2' = X1 + X2 ( V1: V2)

Xe= 1.64 Ω

Am i correct?

rude man
Homework Helper
Gold Member
Is there a load on the secondary? If not, just ignore the secondary winding altogether and solve the circuit with the primary winding only.

Thanks. I will solve it OK now

gneill
Mentor
The problem may be referring to the transformer equivalent model referred to the primary. If so, the results reported by Agata78 in post #2 look correct (although the math as presented is not correct as the turns ratio should be squared in both cases).

rude man
Homework Helper
Gold Member
The problem may be referring to the transformer equivalent model referred to the primary. If so, the results reported by Agata78 in post #2 look correct (although the math as presented is not correct as the turns ratio should be squared in both cases).

If there is no load there is no secondary circuit. There is only a single inductor. The model, turns ratio, secondary leakage inductance and resistance do not matter.

gneill
Mentor
If there is no load there is no secondary circuit. There is only a single inductor. The model, turns ratio, secondary leakage inductance and resistance do not matter.

The problem may be referring to the model alone and not a complete circuit. Or, if you like, consider the secondary to be shorted. The OP would have to put the problem in context to clarify (is the problem associated with a chapter covering the transformer model, for example). Otherwise it's hard to see the point of providing the all the information that's given.

rude man
Homework Helper
Gold Member
The problem may be referring to the model alone and not a complete circuit. Or, if you like, consider the secondary to be shorted. The OP would have to put the problem in context to clarify (is the problem associated with a chapter covering the transformer model, for example). Otherwise it's hard to see the point of providing the all the information that's given.

You can't short the secondary without toxic smoke! This is a power xfmr; look at the primary and secondary winding impedances. The components in the model referring to the secondary winding may be totally removed without affecting the four things asked for in the problem if there is no load.

My suspicion is that either the OP left out load characteristics, or it's a trick question. Probably the former.