When a V-V system is converted into a Δ-Δ system, the capacity of the system increases by ______.

Concept:

Open delta or V-V connection of 3 ϕ transformer:

V-V connection has only two windings instead of three windings in both primary and secondary.

It is used when one winding of transformer goes in maintenance.

Power transfer capacity reduces to 57.7%(or 1/√ 3) times of Δ-Δ connection or closed delta connection.

The capacity of the transformer is measured in VA = √3 V_LI_L

For closed delta, transformer output VA = 3 V_LI_ph

For open delta, transformer output VA =√ 3 VLIph

Calculation:
% increase in capacity = \(\frac{(VA)_{\Delta-\Delta}-(VA)_{V-V}}{(VA)_{V-V}}\times100\)

=\(\frac{3-√3}{√3}\times100\)

= 73.2 %