Solving Question (1)

[shermaine]

I have got some questions posted on this website.
Any one can help me solve it? Pls advise. Thanks.

Q(1) A single-phase, 100kVA, 11000/2200-V, 50Hz transformer has the following parameters:

R at HV = 6.0 ohm
L at HV = 0.08H
Lm at HV = 160H
R at LV = 0.28 ohm
L at LV = 0.0032H
Rc at HV = 125Kohm

(a) Obtain the approximate equivalent circuit of the transformer referred to the low voltage side.

(b) Use this approximate equivalent circuit to determine the efficiency of the transformer when the transformer delivers full load at rated voltage and 0.85 power factor lagging.

(c) When the high-voltage winding of the transformer is connected to a 1100v supply through a cable whose impedance is 1+j3 ohm and a load Z L=50 + j15 ohm is connected to the low-volatge winding, determine the load voltage

(d) At rated voltage, determine the loading of the transformer at which the efficiency is a maximum and calculate this efficiency if the load power factor is 0.6 lagging. Discuss how the power factor will affect the maximum efficiency.

Pls advise.
Thanks.

 

[Nigel Goodwin]

I have got some questions posted on this website.
Any one can help me solve it? Pls advise. Thanks.

Q(1) A single-phase, 100kVA, 11000/2200-V, 50Hz transformer has the following parameters:

R at HV = 6.0 ohm
L at HV = 0.08H
Lm at HV = 160H
R at LV = 0.28 ohm
L at LV = 0.0032H
Rc at HV = 125Kohm

(a) Obtain the approximate equivalent circuit of the transformer referred to the low voltage side.

(b) Use this approximate equivalent circuit to determine the efficiency of the transformer when the transformer delivers full load at rated voltage and 0.85 power factor lagging.

(c) When the high-voltage winding of the transformer is connected to a 1100v supply through a cable whose impedance is 1+j3 ohm and a load Z L=50 + j15 ohm is connected to the low-volatge winding, determine the load voltage

(d) At rated voltage, determine the loading of the transformer at which the efficiency is a maximum and calculate this efficiency if the load power factor is 0.6 lagging. Discuss how the power factor will affect the maximum efficiency.

Pls advise.
Thanks.

This looks like a pretty obvious homework question! - asking other people to do it for you isn't going to help you at all. If you've been asked the question, presumably you've already done enough work to make it within your capabilities?. If you can't do it, it's important that your teacher finds this out - getting someone else to do isn't a good idea!.

 

[shermaine]

Hello,

That's no homework.
It's some question i got ....I have tried and i want to confirm the question.
That's all...

 

[Russlk]

I could have figured it out 40 years ago, but I am too lazy to do it now.

 

[Nigel Goodwin]

I could have figured it out 40 years ago, but I am too lazy to do it now.

Oh! - someone older than me :lol:

I would have said 30 years ago

 

[Painandsuffering]

old.....

I'm only 18 and am learning about transformers. I think it would be very wrong for us to help you with this problem since it does look like an homework assignment unless you post your answers to bounce off of ours!

 

[laroche73]

hmmn...

That's no homework.
It's some question i got ....I have tried and i want to confirm the question.

Sorry, it does look like an obvious homework question (from a textbook). P&S had a good suggestion, post your solutions.