Transformer parallel operation Load Sharing calculator:
Enter the kVA rating of the two transformers and the leakage impedance of the transformer 1 and 2 with the respective input boxes. then press calculates button which displays the accurate results of the total load sharing value of both transformers.
Transformer Load Sharing calculations:
After satisfying the parallel operation condition of the Two transformers will share the load depending upon their leakage impedance only. Here leakage impedance is inversely proportional to the kVA rating.
Let us take two transformer S1(kVA) and S2(kVA) and their leakage impedance Z1(ohm) & Z2(ohm) are connected in parallel with each other.
The total load shared by the transformer 1 is equal to the total kVA rating S(kVA) times of Z2(ohm) divided by the sum of both leakage impedance Z1(ohm) & Z2(ohm).
Here
Z1 = R1 + j X1
Z2 = R2 + j X2
Note: You can find the leakage impedance values in the transformer nameplate details.
Transformer 1 kVA Load Shared = Z2(ohm) x S(kVA) / (Z1(ohm) + Z2(ohm))
In the same way, the transformer 2 shared load is equal to the total kVA rating S(kVA) times of Z1(ohm) divided by the sum of both leakage impedance Z1(ohm) & Z2(ohm).
Transformer 1 kVA Load Shared = Z1(ohm) x S(kVA) / (Z1(ohm) + Z2(ohm))
Example of parallel operation load calculation:
Let us take a simple example, 25kVA, 35kVA two transformers is operating in parallel, find the transformer load sharing for the leakage impedance of 6 ohm & 4.0 ohms.
The total load kVA rating S(kVA) = 25 + 35 = 60 kVA
kVA Shared by the transformer 1 = 4.0 *60 / (6.0+4.0) = 24 kVA
transformer 1 shares 24 kVA from it.
kVA Shared by the transformer 2 = 6.0 * 60 / (6.0+4.0) = 36 kVA
Transformer 2 can share 36 kVA.
You can see that, unequal sharing is occurred because of transformer leakage impedance is not equal, they cannot be loaded parallel their combined kVA rating.
What happens when you load further?
In above, the transformer 2 shares more than the full load kVA rating. If you load the transformer further, the output voltage will get reduce, it causes not able to load transformer2 further with a full load.