I got stuck in a problem while solving the previous exam question for my courseTwo transformers with unequal turn ratio and unequal ratings are connected in parallel and have the same secondary voltage. How will the load be distributed between them? Hence find the circulating current.I know how to find the circulating current when the secondary voltages are different. But how can there be a circulating current if the secondary voltage is same?And I know about the load distribution being inversely proportional to the line impedance of the transformers, but what will be the change taking circulating current into account?
That you may put both the transformers on the same line on their essential aspects however they must have different hundreds at their out places. You ought to use a small load on a 200kva and better load on 500kva. For higher guidance are attempting reffering an electrical engineer near you. I am also an electrical engineer.
To me it is a typical circuit analysis problem. From an application engineers point of view , to analyse the problem, the following needs to be checked first 1) Open circuit Voltage of both the TRXs 2) Internal impedences of TRXs 3) Total Load to be catered to ( converted to in terms of Z) 4) Ratings of the TRXs ( Rather allowable current that can be drawn from each TRXs) Having known first three quantities , we can make the parallel circuts and calculate the current in each branch ( through TRX1, TRX2, and the load) andtheir directions The fourth quantity will tell us if loading is within limit or not.
If I understand this correctly, then you have this situation, let T1 be the first transformer and T2 the second one The input voltage is connected to the primary of T1 The secondary of T1 is connected to the primary of T2 the secondary of T2 is connected to the load If the secondaries are at the same voltage then T1 secondary voltage T1 primary voltage T2 secondary voltage. This can only happen if the turns ratio of T2 is 1:1, i.e it has the same number of turns on the primary and the secondary. Does that help?
Think of it this way - the two transformers are connected in parallel on the primary. They have different turns ratios. As a consequence, they want to produce different open circuit secondary voltages. But the fact that they are also connected in parallel on the secondary means that the secondary voltages must be the same. So what happens is that the DIFFERENCE between the open circuit secondary voltages is the voltage that drives the circulating current between the transformers. You didn't mention the impedances of the transformers. If you have transformers with equal nameplate impedances but different ratings in parallel, load will split between them in proportion to their respective ratings. Except for losses, the circulating current is reactive and not 'load'.
