billyray
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1. Homework Statement
A 415V to 11 kV transformer has a rating of 200 kVA. The winding resistance and leakage reactance when referred to the primary are 0.014 Ω and 0.057 Ω respectively.
(b) In designing a particular 415V to 11 kV, 200 kVA transformer, the primary winding resistance is to be 10 mΩ. Find the maximum winding resistance of the secondary winding if the transformer is to have 2% regulation at unity power factor.
they are included
I am working from a Hughes electrical book to get my equations but the forums I have looked at do not agree with my answers. the book seem a good place to get the equations though
is this all i need RS = [ R'P - RP ] * n^2
In a previous post the equations by rude man go further than mine by a more complex method. I presume he's right
: assume primary current = ip.
Then primary resistance power loss is Pp = ip2 Rp
But if we reflect into the secondary the power loss must be the same: Ps = is2 Rs.
But is/ip = N1/N2 so Ps = (N1/N2)2 ip2 Rs = ip2 Rp.
So Rp = (N1/N2)2 Rs
or Rs = (N2)/N1)2 Rp. For your step-up transformer, (N2/N1) = 702.56
so Rs = 702.56 Rp.
i am very worried about this he seems to go further than the book which does not account reflection. Is this because of the unity involved?
I tried hard to get this far but i feel i have missed something not in my book. Transformers are something i don't look at at all. Also have I asked too much for help because no one seems to reply.i rushed the second equation mixing up v1 and v2 it had been a week since i did first question i did not look at question and concentrated on answer so mucked up. i will try again
1. Homework Statement
A 415V to 11 kV transformer has a rating of 200 kVA. The winding resistance and leakage reactance when referred to the primary are 0.014 Ω and 0.057 Ω respectively.
(b) In designing a particular 415V to 11 kV, 200 kVA transformer, the primary winding resistance is to be 10 mΩ. Find the maximum winding resistance of the secondary winding if the transformer is to have 2% regulation at unity power factor.
Homework Equations
they are included
The Attempt at a Solution
I am working from a Hughes electrical book to get my equations but the forums I have looked at do not agree with my answers. the book seem a good place to get the equations though
is this all i need RS = [ R'P - RP ] * n^2
In a previous post the equations by rude man go further than mine by a more complex method. I presume he's right
: assume primary current = ip.
Then primary resistance power loss is Pp = ip2 Rp
But if we reflect into the secondary the power loss must be the same: Ps = is2 Rs.
But is/ip = N1/N2 so Ps = (N1/N2)2 ip2 Rs = ip2 Rp.
So Rp = (N1/N2)2 Rs
or Rs = (N2)/N1)2 Rp. For your step-up transformer, (N2/N1) = 702.56
so Rs = 702.56 Rp.
i am very worried about this he seems to go further than the book which does not account reflection. Is this because of the unity involved?
I tried hard to get this far but i feel i have missed something not in my book. Transformers are something i don't look at at all. Also have I asked too much for help because no one seems to reply.i rushed the second equation mixing up v1 and v2 it had been a week since i did first question i did not look at question and concentrated on answer so mucked up. i will try again
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