kVA to amps conversion is the process of working out the electrical current that flows for a given apparent power at a given voltage. It answers a practical question: if my load is rated at 100 kVA, how much current will it draw? That current figure is what you need to select conductors, circuit breakers, fuses, and transfer switches. It is also the full-load current a generator alternator must supply — the figure every generator datasheet lists.
Amps = (kVA × 1000) ÷ (√3 × Volts)
√3 ≈ 1.732 — the three-phase constant.
Amps = (kVA × 1000) ÷ Volts
The √3 factor disappears for single-phase circuits.
kVA = (√3 × Volts × Amps) ÷ 1000
Use this when you know the current.
No. When you convert kVA to
amps, power factor does not enter the
calculation. kVA is apparent power,
the total power the supply must deliver. It already
includes both real power and reactive power. The
current that corresponds to that apparent power is
fixed by the voltage and phase configuration.
Power factor only matters when you work from
kilowatts:
Amps = (kW × 1000) ÷ (√3 × Volts × PF)
For the same kVA, a three-phase system draws √3 (about 1.732) times less current per conductor than a single-phase system.
The amps figure is the full-load current a generator alternator must deliver — critical for cable and breaker sizing.
At 400 V three-phase, full-load current is about 1.44 amps per kVA. At 480 V, about 1.20 amps per kVA.
Enter the apparent power (kVA), system voltage and phase configuration to get the line current in amps. The tool also shows the real power (kW) at your chosen power factor, and compares single-phase vs. three-phase current for the same kVA.
Select phase, voltage, and kVA or amps to convert.
For quick reference, the table below lists the three-phase line current for common generator kVA ratings at 400 V (IEC/global standard) and 480 V (North American industrial). These values are for balanced loads at standard voltages.
| Generator kVA | Amps @ 400 V | Amps @ 480 V |
|---|---|---|
| 25 kVA | 36.1 A | 30.1 A |
| 50 kVA | 72.2 A | 60.1 A |
| 100 kVA | 144.3 A | 120.3 A |
| 250 kVA | 360.9 A | 300.7 A |
| 500 kVA | 721.7 A | 601.4 A |
| 1000 kVA | 1443.4 A | 1202.9 A |
| 2500 kVA | 3608.5 A | 3007.1 A |
The conversion from kVA to amps is grounded in basic electrical theory. Whether you are sizing a generator, selecting cable, or designing a distribution board, the formula gives you the line current that must be carried. Here is how it works — and why √3 appears.
Amps = (kVA × 1000) ÷ (√3 × Volts)
For a balanced three-phase system, the line current is
determined by dividing the apparent power (in volt-amperes)
by the product of √3 and the line-to-line voltage.
Amps = (kVA × 1000) ÷ Volts
In a single-phase circuit, the √3 factor drops out.
The current is simply the apparent power divided by
the voltage.
The square root of three appears because a three-phase supply delivers power continuously across three conductors that are 120° out of phase. Dividing by √3 accounts for the fact that the three phases share the load, so each conductor carries less current than an equivalent single-phase circuit.
kVA = (√3 × Volts × Amps) ÷ 1000
When you know the current, you can work backward to
find the apparent power. This is useful when you are
measuring an existing load.
kW = kVA × PF
Real power (kW) is apparent power (kVA) multiplied by
power factor. At the standard generator PF of 0.8, a
100 kVA generator delivers 80 kW.
Amps = (100 × 1000) ÷ (1.732 × 400) = 144.3 A. At 0.8 PF, real power = 80 kW. If this were single-phase at the same voltage, current would be 250 A — 1.732× higher.
The kVA-to-amps calculation is just the start. For generator applications, altitude, temperature, motor starting methods, and duty cycle all influence the final capacity selection.
Engine output decreases as air density falls. A planning estimate of roughly 1% loss per 100 m above 1,000 m means a site at 3,000 m may have substantially less available output.
High ambient temperature reduces cooling effectiveness and usable output. Above approximately 40 °C, additional derating may be required for hot climates.
Direct-on-line motors can draw around 6–7× full-load current during startup. Star-delta starters, soft starters and VFDs reduce the transient demand and can allow a smaller set.
Standby generators operate intermittently during utility failures, while prime-rated sets are designed for extended operation. The required rating should reflect the actual duty cycle.
UPS systems, VFDs and electronic loads can introduce harmonics. If non-linear loads form a large percentage of the system kVA, alternator sizing requires additional consideration.
Planned equipment additions should be considered before ordering the set. Allowing approximately 10–25% reserve can reduce the risk of replacing an otherwise suitable generator.
Final generator selection should be checked against the complete load schedule, motor-starting sequence, power factor, site conditions, duty rating and selected engine-alternator combination before equipment is ordered.
At Shandong Huali Electromechanical Co., Ltd., we manufacture diesel generator sets from 8 kVA to 4000 kVA, engineered for continuous industrial operation with over 25 years of manufacturing experience and strict pre-delivery testing on every unit. If your calculation points to a load we can serve, our engineers will confirm the correct rating for your application.
A: Divide kVA by the product of √3 and the line-to-line voltage: Amps = (kVA × 1000) ÷ (1.732 × Volts). For example, 100 kVA at 400 V is 144.3 A.
A: At 400 V three-phase, a 100 kVA generator delivers about 144 amps. At 480 V, the same machine delivers about 120 amps. Higher voltage means lower current for the same power.
A: No. kVA is apparent power, which already includes the full load current. Power factor only enters the calculation when you convert from kilowatts using Amps = (kW × 1000) ÷ (1.732 × Volts × PF).
A: For the same kVA, a single-phase circuit draws 1.732 times more current than a three-phase circuit. Three-phase power distributes the load across three conductors, so each carries less current — the reason industrial systems are three-phase.
A: Yes. Convert kW to kVA first by dividing by power factor (kVA = kW ÷ PF), then apply the kVA-to-amps formula. Or use the combined formula Amps = (kW × 1000) ÷ (1.732 × Volts × PF).
A: The square root of three (≈1.732) appears because a three-phase supply delivers power across three conductors that are 120° out of phase. It is the ratio between line-to-line voltage and line-to-neutral voltage in a balanced system.
