Correct Answer - Option 3 : 259 kVA

Open-Delta Connection:

- An open delta connection transformer uses two single-phase transformers to provide a 3-phase supply to the load.
- An open-delta connection system is also called a V-V system.
- The Open-delta connection system is usually only used in emergency conditions, as its efficiency is low when compared to the delta-delta (Closed delta) system.
- The total load carried by an open delta system is 57.7% of the closed delta system.

**The capacity of open-delta system = √3 × Rating of one transformer**

= 0.577 × Rating of the closed delta system

Calculation:

Given,

Rating of one transformer = 150 kVA

The capacity of open delta system = √3 × Rating of one transformer

= √3 × 150 = 259.8 kVA

**Therefore, the maximum three-phase load that they can carry is 259.8 kVA**