Paralleling Two Transformers

To parallel XFMRS they must be matched, voltage and impedance. IF not..one of them will greatly over heat...lot of gassing from the core iron as well as the winding. The cellulose insulation will degrade rapidly.

For parelleling of Trs the following conditions have to be satisfied.

1.Trs should have same percentage Impedance,same Voltage ratio,and Same phase sequence.

As others have said above none of the parameters match except the output voltage! Is this a homework question?

Can you please provide more information on your application (or is this just a theoretical question).

hello,

in paralelling Tx, you should consider 4 items which mandatory (frequency, voltage, impedance, vector group). Even the vector group is different between Tx, there is still connection configuration that allow parallel operation.

Connection can be classified in four groups:

¨ Group I contains hour numbers 0, 4 and 8

¨ Group II contains hour numbers 6,10 and 2

¨ Group III contains hour numbers 1 and 5

¨ Group IV contains hour numbers 7 and 11

i do not think that your transformers can be operated in parallel.

Let me add some information for you.

The necessary for parallel operation

Transformers of unequal kVA ratings will share a load practically ( but not exactly) in proportion to their ratings, providing that the voltage ratios are identical and the percentage impedances (at their own kVA rating) are identical, or very nearly so in these cases a total of than 90% of the sum of the two ratings is normally available.

It is recommended that transformers, the kVA ratings of which differ by more than 2:1, should not be operated permanently in parallel.


Other condition necessary for parallel operation

1- All paralled units must be supplied from the same network.
2- Secondary cabling from the transformers to the point of paralling have approximately equal length and characteristics.
3- Voltage difference between corresponding phase must not exceed 0.4%

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What about vector grouping here?

nope, the transformers described can not be paralleled.

Well, you could parallel them but it would destroy them, as the other guys said

can't do both Tx's in parrallel operation. because the secondary of one TX is delta connected and the other os star connected.

And check other friends replys also.

Answering your question about different voltage-ratios, regardless of impedances X/R ratios differences: consider transformer A with a 400-V as its secondary no-load voltage, while B's is 415-V; further, let Za and Zb represent the impedance in ohms, of transformer A and B, respectively. Then the circulating current, equals,

Ic = [Vb (higher secondary voltage) � Va (the lower secondary voltage] / [Za + Zb], Amps

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Referring to the above given formula

the given formula is completely wrong the formula u gave is just used to find out the current (i) and not for the paralleling of two transformers.

It is a completely different concept of Electrical Engineering

Refer - Parallel Operation Of Transformer

Yes agree, above given formula is totally wrong, formula give you only current which we used not paralleling of two transformers.

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