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Dry-Type Transformer Sizing | Engineering Database

Dry-Type Transformer Sizing

electrical

Selects the next-size-up dry-type transformer for a given load and calculates partial-load losses, efficiency, heat output, secondary full-load amps, available fault current, and voltage regulation.

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Load Kva*

Total connected load in kVA that the transformer must serve. The tool selects the next standard size at or above this value. Sum of all connected loads. Typical: 45-225 kVA for commercial floors, 500-2500 kVA for buildings.

Primary Voltage

Transformer primary (line) voltage in volts. Common values: 480, 600, 4160, 12470, 13200, 13800. If omitted, defaults to 480 V.

Secondary Voltage

Transformer secondary (line) voltage in volts. Common values: 120, 208, 240, 277, 480. If omitted, defaults to 208 V.

Phases

Number of phases. Use 1 for single-phase or 3 for three-phase transformers. If omitted, defaults to 3 (three-phase).

Load Power Factor

Power factor of the connected load (dimensionless, lagging). Typical range 0.80-0.95 for commercial/industrial loads. If omitted, defaults to 0.85.

Ambient Temp C

Maximum ambient temperature in degrees Celsius at the transformer location. NEMA TP-1 standard rating is 40 C; derate above this. Typical: 40 C (NEMA standard rating). Derate for enclosed or high-temp rooms. If omitted, defaults to 40 C (NEMA standard).

Reference data

This calculator pulls live values from the following engineering reference tables in the database.

transformer data

About this calculator

Dry-Type Transformer Sizing is part of the Engineering Database calculator suite. Each tool runs deterministic calculations against authoritative reference data and code-compliant methods, so results are reproducible and traceable to source standards.

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