Open-Delta Transformer Capacity Calculator
Estimate balanced open-delta bank capacity from two equal transformer units and compare it with a three-unit closed-delta bank.
Enter nameplate or test values
Balanced open-delta capacity
About this calculator
Estimate balanced open-delta bank capacity from two equal transformer units and compare it with a three-unit closed-delta bank.
Assumes equal units and balanced three-phase loading. Excludes unequal transformers, mixed lighting and power loads, protection selection, and manufacturer limitations.
Method and assumptions
For two equal transformer units each rated S kVA, ideal balanced open-delta capacity is √3 × S. The corresponding three-unit closed-delta capacity is 3 × S, so open-delta capacity is approximately 57.7% of that value.
Enter manufacturer nameplate or test data for the exact transformer and operating condition. Default values are examples and should be replaced with project data.
FAQs
Does this provide wiring or switching instructions?
No. It estimates electrical quantities from entered values. Follow manufacturer diagrams, safe work procedures, and qualified design review for any equipment application.
Are these results equipment approval or certification?
No. Confirm ratings, test conditions, load profile, thermal limits, and applicable installation requirements independently.
Sources
Transformer nameplate or test data supplied by the user and the ideal relationships described above.