Homework Help

[Bharath S]

Hi,
I wanted to know what effects will the primary inductance of a non-ideal transformer have when the secondary is shorted and also when opened?Can you please give a formula to calculate them. And also what effects the secondary inductance will have when the primary is shorted and also opened? Can you give a formula for this as well.

Any help is really appreciated. And thanks in advance

 

[ramuna]

Hi,
As your primary reference for this question, use: **broken link removed**

Decomposing your multipart question into its components, and treating each one with reference to sections in the above paper, we have:
1) what effects will the primary inductance of a non-ideal transformer....
Refer to section 2.15. This shows what you need to do, in order to convert the ideal transformer model into the non-ideal.

2) what effects will the primary inductance of a non-ideal transformer have when the secondary is shorted and also when opened ?
Refer to section 2.14. This explains secondary to primary impedance transformation. Apply those explanations to your two situations. In addition to this, you will need to consider the effect of the most important non-ideality, given in the top paragraph on page 21. Formulas are in the appropriate sections of that paper.

3) And also what effects the secondary inductance will have when the primary is shorted and also opened?
The primary should not be shorted (by which I understand that a wire is connected between the ends of the primary winding). Why would this be so ?
If the primary is open-circuited (by which I understand that only one end of the primary winding is connected to the AC source), how much current would be passing into the primary winding ?

 

[Bharath S]

Thanks for the help Ramuna.My understanding of transformers is pretty primitive so I further wanted to ask, during Impedance Transformation what do I do when the secondary is just shorted rather than connecting a load?
And regarding shorting the primary. I do know that the primary should not be shorted, but my Professor wants to know the effect of doing so. Please do help me if you can on this.

Thanks

 

[ramuna]

Hi,
Both of your questions depend on knowing what is the impedance of a short (or, to give it its full name, a short circuit). The easiest way to answer this, is to compare it with its opposite, the open circuit. Consider two situations. One where a known voltage source is applied to a short-circuit, and the other where the same source is applied to an open circuit. What do you think the currents involved will be in each situation ? Having estimated those, apply Ohm's law to derive the impedances.