What Is kVA in a Transformer Rating

Learn how it relates to voltage, current and load duty when comparing equipment.

kVA is the unit of apparent power used in transformer ratings. Learn how it relates to voltage, current and load duty when comparing equipment.

Read the rating as a complete set

One kVA equals 1,000 volt-amperes. For single-phase AC, apparent power is S = V × I / 1,000. For balanced three-phase AC, S = √3 × VLL × IL / 1,000. A 480 V, 100 A balanced three-phase example is 83.1 kVA. Read voltage, phase, frequency and cooling conditions with the capacity rating.

Read the apparent power rating. Illustrative balanced three-phase calculation.

Example — balanced three-phase apparent power

S = √3 × VLL × IL / 1,000

√3 × 480 V × 100 A / 1,000 ≈ 83.1 kVA

This is an illustrative line-value calculation for a balanced system. Confirm voltage basis, winding connection and equipment conditions on the approved nameplate and schedule.

Separate kVA from the connected load

The transformer has a rated duty, while the facility has an operating load profile. Compare simultaneous demand, peaks, starting loads and planned expansion to the equipment rating. Check voltage, phase, frequency, cooling and ambient conditions together when reading a nameplate.

Item or condition	What to compare	Input or result
Rated kVA	Equipment apparent-power capacity	Read with nameplate conditions
Load kVA	Operating apparent-power demand	Build from the load profile
Current	Depends on voltage and phase	Use the matching formula

kVA is apparent power. Real power in kW also depends on power factor; current depends on system voltage and phase. Keep these quantities labelled separately in the project load schedule. See how power factor affects capacity for a worked comparison.

Choose the next calculation

Use the current calculator when voltage and kVA are known. Use the kW conversion page when active load and power factor are known. Follow the sizing guide to turn the calculation into a product enquiry.

kVA and current

Convert between apparent power and current using the matching voltage and phase.

kVA and kW

Use power factor to relate apparent power to active power.

Transformer sizing

Organize demand, peaks, allowance and site data for a project enquiry.

Frequently Asked Questions

Does 500 kVA mean 500 kW?

It equals 500 kW only at unity power factor. Active power in kW is kVA multiplied by power factor.

Does the same kVA mean the same dimensions?

Dimensions also depend on voltage class, construction, cooling and the selected configuration.

Apply the rating to your project

Share the nameplate conditions, voltage, phase, frequency, load profile and installation when reviewing transformer capacity.