What will happen if two transformer are connected in parallel with unequal impedance?

Same Polarity The transformers should be properly connected with regard to their polarity. If they are connected with incorrect polarities then the two emfs, induced in the secondary windings which are in parallel, will act together in the local secondary circuit and produce a short circuit.

Does impedance change in transformer?

As the load current increases, transformer winding temperature also increases and hence its impedance and thus the voltage drop.

Which of the following is not a condition for parallel operation of two transformers?

Explanation: The transformers must have the same voltage-ratio to avoid no-load circulating current when transformers are in parallel on both primary and secondary sides. Since the leakage impedance is low, even a small voltage difference can give rise to considerable no-load circulating current and extra I2R loss. 11.

What are the conditions for parallel operation of 3 phase transformers?

Condition for Parallel Operation of Three Phase Transformers The line voltage ratio of the transformers must be same. The transformers should have equal per unit leakage impedance. (You may read per unit system) The ratio of equivalent leakage reactance to equivalent resistance should be same for all the transformers.

What is the need for parallel operation of transformer?

The parallel operation of a transformer has some advantages likes it increases the efficiency of the system, makes the system more flexible and reliable. But it increases the short-circuit current of the transformers.

How can we increase the impedance of a transformer?

The only way to change resistance of a transformer is to use thicker conductor in winding. First measure the resistance of the winding and the find out the current rating of the coil. Then find out a rheostat of that current capacity and the equivalent power rating(I^2*R). Connect it in series with the coil.

What affects transformer impedance?

The percent impedance is the percent voltage required to circulate rated current flow through one transformer winding when another winding is short-circuited at the rated voltage tap at rated frequency. \%Z is related to the short circuit capacity of the transformer during short circuit conditions.

Which of the following condition should be fulfilled for parallel operation of two transformers?

Various conditions that must be fulfilled for the successful parallel operation of transformers: Same voltage and Turns Ratio (both primary and secondary voltage rating is same) Same Percentage Impedance and X/R ratio. Identical Position of Tap changer.

What is the need of parallel operation of transformer?

Necessity of Parallel Operation of Transformers Increased Load: When load is increased and it exceeds the capacity of existing transformer, another transformer may be connected in parallel with the existing transformer to supply the increased load.

Do all Transformers that run in parallel have the same impedance?

In other words, percentage impedance or per unit values of impedance should be identical for all the transformers that run in parallel. Polarity of all transformers that run in parallel, should be the same otherwise huge circulating current that flows in the transformer but no load will be fed from these transformers.

Is impedance of Transformers inversely proportional to their MVA ratings?

From the above two statements it can be said that impedance of transformers running in parallel are inversely proportional to their MVA ratings. In other words percentage impedance or per unit values of impedance should be identical for all the transformers run in parallel.

How many kVA transformers can be connected in parallel?

Example: Connecting 3000 kVA and 1000 kVA transformers in parallel, each with 5.75\% impedance, each with the same turn ratios, connected to a common 4000 kVA load.

Can two Transformers share the same phase shift?

Satisfactory parallel operation can occur only when the two transformers belong to the same group and have the same phase shift. The two transformers must have a compatible range of internal impedance to allow effective load sharing across the load range.