Transformer Sizing Calculator
Enter load current, operating voltage, phase type, and design allowance to calculate required kVA, select a standard catalog rating, and determine rated full-load current.
Use the Transformer Sizing Calculator
Load & System Parameters
User-specified margin for future growth or duty allowance (0–100%). Does not replace a code-mandated continuous load calculation.
Sizing Summary
Enter load parameters and click Calculate.
Recommended Standard Rating
Standard Series Basis: Ratings follow the North American low-voltage dry-type increments documented in Eaton's catalog. Availability, efficiency classes, temperature rises, and impedance vary by manufacturer and project specifications.
Summary
Enter load current, operating voltage, phase type, and design allowance to calculate required kVA, select a standard catalog rating, and determine rated full-load current.
How it works
- Select the circuit phase: single-phase (line-to-neutral or line-to-line single phase) or balanced three-phase (line-to-line).
- Enter total load current in amperes (A).
- Enter nominal operating voltage in volts (V).
- Enter an optional design allowance percentage (default 25%) for spare capacity or load growth.
- Review the calculated load kVA, required apparent power, next standard catalog rating, rated FLA, and operating load percentage.
Use cases
- Preliminary sizing of general-purpose low-voltage distribution transformers.
- Determining transformer rated full-load current (FLA) at operating voltage.
- Checking operating load percentage against a planned standard transformer capacity.
- Comparing apparent power requirements between single-phase and balanced three-phase distribution.
- Engineering feasibility checks prior to detailed feeder and overcurrent protection design.