Transformer Calculations

Transformer calculations: choose the quantity you need

Match every rating to the correct winding and phase configuration. Primary and secondary voltages produce different currents even when they share an apparent-power rating.

Transformer kVA to amps — Calculate primary and secondary current separately using each winding voltage.

Small-transformer VA to amps — Convert control-transformer apparent power to winding current.

Primary and secondary current — Explore the relationship between winding voltage and current.

Transformer impedance percentage — Work with impedance on the stated electrical base.

Transformer iron and copper losses — Distinguish no-load loss from load-dependent conductor loss.

Cable and conductor calculations — Continue with separate ampacity and voltage-drop checks.

A calculated winding current does not by itself specify a fuse, breaker or conductor. Review each tool’s assumptions and the actual equipment data. The archive below includes additional transformer topics.