Direct current
U = P / (I * η)
U₀ = P / (I * cosφ * η)
U = P / (I * cosφ * η)
U = P / (√3 * I * cosφ * η)
η = Efficiency(%)
P = Power (W)
U₀ = Voltage [L - N] (V)
U = Voltage L - L
I = Current(A)
cosφ = Power factor
Calculate your motor’s actual operating voltage from current, power, and PF. Validate against nameplate rating with tolerance checks. Supports single, two, and three-phase AC systems.
Input motor parameters to automatically calculate:
Operating voltage (V)
Supports single-, two-, and three-phase AC systems
Real-time calculation from measured current, power, and power factor
Voltage validation against typical nameplate ratings (e.g., 230V, 400V, 460V)
| System Type | Formula |
|---|---|
| Direct current | U = P / (I × η) |
| Alternating single-phase | U₀ = P / (I × cosφ × η) |
| Alternating two-phase | U = P / (√2 × I × cosφ × η) |
| Alternating three-phase | U = P / (√3 × I × cosφ × η) |
P: Output mechanical power (shaft power) in kilowatts (kW)
I: Line current in amperes (A)
cosφ: Power factor (PF), dimensionless, between 0.0 and 1.0
η: Motor efficiency as a decimal (e.g., 90% → 0.90)
Three-phase motor, I = 10 A, P = 5.5 kW, PF = 0.85 →
V = 5.5 / (√3 × 10 × 0.85) ≈ 373.6 V
→ This is 6.6% below a standard 400V nameplate. May indicate undervoltage or supply issues.
Single-phase motor, I = 5 A, P = 0.92 kW, PF = 0.8 →
V = 0.92 / (5 × 0.8) = 230 V
→ Matches common 230V residential rating. Operating within normal range.
1.Measure under steady-state load (not startup or idle)
2.Use calibrated instruments that report true RMS power and PF
3.Verify phase balance in three-phase systems
4.Always compare results to the motor’s nameplate voltage
1.Maintenance engineers troubleshooting motor overheating or tripping
2.Electricians verifying installation quality after wiring
3.Facility managers auditing power quality across plants
4.Technical students learning real-world motor behavior
1.Input data must reflect steady-state (running) conditions — not startup surge
2.Voltage cannot be negative; verify measurement polarity and sensor calibration
3.Use high-precision instruments — many basic clamp meters misread power factor
4.Operating voltage varies with load; measure under typical operating conditions
5.Always compare results to the motor’s nameplate before making operational decisions
No. DC motors do not use power factor, and this tool is designed for AC systems only.
The nameplate shows the rated (design) voltage. Actual operating voltage depends on your supply, cable length, and load. Differences within ±5% are generally acceptable per NEMA standards.
No. This calculator determines the actual voltage your motor is seeing based on real measurements. It does not simulate compatibility. Running a 240V motor on 120V typically causes overheating and failure.
For estimation:
Three-phase induction motors: assume PF ≈ 0.85 at full load
Small single-phase motors: PF ≈ 0.7–0.8
For accuracy, measure with a power analyzer or clamp meter that supports PF.
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