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In calculating kVa sizing for a single-phase transformer, the correct formula involves understanding the relationship between voltage (V), current (I), and power, expressed in kilovolt-amperes (kVa). The standard unit for measuring power in kVa for electrical systems is based on using a factor of 1,000.

The correct formula is:

kVa = V x I / 1,000

This formula works because it converts the product of voltage and current (which gives you power in volt-amperes) into kilovolt-amperes by dividing by 1,000. This factor is essential since kilovolt-amperes represent a thousand volt-amperes.

Choosing 100,000 or 10,000 as a divisor would incorrectly scale the calculated value, leading to inaccuracies in determining the necessary transformer size. Similarly, using 100 would give a power measurement that is not aligned with standard electrical calculations for kilovolt-amperes.

Thus, recognizing the relevance of the divisor is critical, and using 1,000 aligns with common industry practice, ensuring proper sizing of transformers to handle the anticipated loads.