Transformer Fundamentals
Three Phase Transformers and Connections
Specify capacity, line voltages, frequency and winding connection together, then match the construction to the installation.
A three phase transformer transfers power between three-phase circuits at the required voltage ratio. Specify capacity, line voltages, frequency and winding connection together, then match the construction to the installation.
Read line ratings consistently
For a balanced system, apparent power is S = √3 × VLL × IL. A 500 kVA unit at 480 V has approximately 601 A rated line current on that side. Record which side of the transformer each voltage and current refers to when comparing quotations.
Example — balanced three-phase line current
IL = 1000 × kVA / (√3 × VLL)
500 kVA at 480 V → approximately 601 A
Capacity is an apparent-power rating; voltage and current describe a specific line and transformer side. Confirm the nameplate and system design.
Specify the winding connection
Delta and wye connections affect line-to-phase relationships and the available neutral. State the vector group or phase displacement required by the system. For parallel operation, coordinate ratio, phase sequence, displacement and impedance with the project engineer.
Instrument transformers support the metering and protection design. Read the current transformer guide. If you are still comparing service arrangements, see single-phase vs three-phase power.
| Item or condition | What to compare | Input or result |
|---|---|---|
| Capacity example | 500 kVA at 480 V | About 601 A line current |
| Connection | Delta or wye on each side | Neutral and phase displacement |
| Installation | Pad-mounted, indoor or power duty | Site and system specification |
Route the specification to a family
A ground-level cable network may use a three-phase pad-mounted unit. Indoor projects may require dry-type construction, while higher-voltage network duties belong to the power-transformer family. Confirm enclosure, cooling, cable entry and required drawings with the selected configuration.
Frequently Asked Questions
Are line voltage and phase voltage the same?
They are equal across a delta winding. For a balanced wye winding, line voltage is √3 times phase voltage.
Which product page should hold the final ratings?
Use the selected model page and approved technical schedule for its capacity, voltage, dimensions and accessories.
Prepare a complete three-phase specification
Share capacity, both line voltages, frequency, winding connection, phase displacement, neutral, installation and required drawings.