Transformer Calculators

Size transformer overcurrent protection per NEC Table 450.3(B) and determine minimum conductor sizes for primary and secondary circuits.

2 Calculators NEC Article 450 Free to Use

Transformer OCPD Sizing

NEC 450.3

Calculate maximum overcurrent protection device ratings for transformer primary and secondary per Table 450.3(B) — transformers 600 volts or less.

Transformer Conductor Sizing

NEC 450.3, 310.16

Determine the minimum conductor size for transformer primary and secondary circuits based on full-load current and the 75°C copper ampacity column.