Transformer Engineering Calculators
Transformer kVA selection, full-load current, loading, efficiency, losses and voltage regulation calculators with formulas and worked examples.
Choose the rating first, then check how the transformer behaves. Selection takes the load, power factor, growth and target loading to a standard size. The current and loading calculators give the rated current on each side and the spare capacity from measurements. Efficiency and regulation show the losses and the secondary voltage under load.
Where to start
- Transformer kVA Selection: Required rating from load, power factor, growth and target loading, rounded to a standard size.
- Transformer Full-Load Current: Rated line current on either side, for cables and breakers.
- Transformer Loading from Measurements: Present loading and spare capacity from measured current.
- Transformer Voltage Regulation: Secondary voltage drop under load.
All 5 calculators in this category
Transformers
- Transformer Full-Load Current: Rated line current on either side of a transformer. Open in Elecmetric
- Transformer Voltage Regulation: Secondary voltage drop under load from impedance, resistance, load and power factor. Open in Elecmetric
- Transformer Efficiency and Losses: Efficiency at any load, total loss, and the load at which efficiency peaks. Open in Elecmetric
- Transformer kVA Selection: Required transformer rating from load, power factor, growth and target loading, rounded to a standard size. Open in Elecmetric
- Transformer Loading from Measurements: Present loading and spare capacity from measured secondary current. Open in Elecmetric
Also useful here
These sit in other categories but apply to the same work.
- Maximum Demand: Coincident maximum demand from connected load, demand factor and diversity factor. Open in Elecmetric
- Transformer Fault Current: Prospective three-phase fault current at a transformer secondary. Open in Elecmetric
What these calculators do not cover
Harmonic-rich loads, motor starting, ambient temperature and overload duty can call for a larger or specially rated unit. Standard sizes are the lists shown on each calculator, so confirm availability with your supplier. The transformer fault current calculator gives an upper bound that ignores source and cable impedance.
Cross-check: all 7 calculators listed here are compared with 122 reference calculations written separately from the engine. This confirms the arithmetic and selection rules. It does not confirm that a standard table or convention matches your standard or manufacturer data.
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