Transformers

Transformer sizing and fault-analysis calculators: full-load current on primary and secondary, standard kVA sizing, and secondary short-circuit current from nameplate %Z, with and without source impedance.

Transformer Sizing & Full-Load Current Calculator

Primary and secondary full-load current from transformer kVA rating, plus the nearest standard size.

Transformer Impedance & Short-Circuit Current Calculator

Symmetrical, peak, and RMS asymmetrical secondary fault current from transformer %Z and X/R ratio.

Studies that use transformers calculators

Study

Low-Voltage Feeder Study

Feeder sizing end to end from one set of inputs — transformer full-load current, three-phase load current, voltage drop over the run, conductor ampacity after derating, and the reactive power for a target power factor — each showing its full worked solution.

Study

Transformer Fault & Motor-Starting Study

Available fault current at a transformer secondary, from nameplate %Z and the utility's contribution — with symmetrical and asymmetrical duty from the combined X/R ratio, and the voltage dip a motor start causes on that same bus.