Transformer Calculator | Kewo Engineering

Transformer

Rating Rating, otherkVA Load Spare capacity% Primary voltage Primary, otherV Secondary system Impedance, nameplate%Z

Protection

Table 450.3(B)

Method Devices Primary device Secondary device

Conductors

Primary Secondary Insulation Terminal temperature rating Secondary neutral

Size for the rated current as a continuous load (125 %) Primary: next standard device above the ampacity, 240.4(B) Neutral carries nonlinear load, 310.15(E)(3)

Choose the sizes

Largest size before paralleling Primary size Primary sets Secondary size Secondary sets

Automatic finds the smallest size that meets the code. A chosen size is checked, and the grounding conductor grows with it (250.122(B)).

Installation

Primary raceway Secondary raceway Primary lengthft Secondary lengthft Secondary conductors Ambient temperature°C On a rooftop

Bare grounding and bonding conductors

Voltage drop

Power factor Limit for each run%

Increase conductor size for voltage drop

Report details

Location Prepared by Reference

Transformer circuit

Primary

Secondary

Grounding and bonding

Raceways, to scale

Conductors from NEC Chapter 9 Tables 5 and 8

Transformer

Inputs

Basis

NEC 2023. Transformer protection by Table 450.3(B); device ratings by 240.6(A). Primary conductors protected by 240.4 and 240.4(B); secondary conductors by 240.21(C), without the next-size-up rule.

Ampacity from Table 310.16 with Table 310.15(B)(1)(1) and Table 310.15(C)(1), limited by the terminal temperature (110.14(C)). Grounding and bonding by 250.30, 250.122, Table 250.102(C)(1) and Table 250.66. Raceway fill by Chapter 9 Tables 1, 4, 5 and 8.

Voltage drop with Chapter 9 Table 9 at 75 °C and the stated power factor, at the rated current. Fault current at the secondary terminals with an infinite primary source.