Transformer Open Delta Connection

Open Delta Connection Definition

An open delta connection transformer uses two single-phase transformers to create a three-phase supply, typically used in emergencies.

Efficiency

Open delta systems are less efficient than closed delta systems because they provide less power output while operating at full transformer capacity.

Calculation Formula

The capacity of an open delta system is found by multiplying the square root of three with the rating of one transformer, resulting in a lower total power output compared to a closed delta system.

Capacity of open delta system = 0.577 x rating of closed delta system=0.577 x 30 kVA= 17.32 kVA

Diagram

The connection diagram shows how two transformers supply a three-phase load with a unity power factor, illustrating the system’s operation.

Load Distribution

In an open delta system, each transformer supplies 10 kVA, totaling 17.32 kVA, demonstrating how power is distributed and why efficiency drops.