Free Engineering Tool
Three-Phase Motor Power Calculator
Calculate shaft output power P = √3 × V × I × cos φ × η for three-phase motors. Bidirectional — solve for any variable. Also shows apparent & reactive power.
Results
Three-Phase Power Formula
The mechanical shaft output power of a three-phase motor (electrical input × efficiency) is:
- P — shaft output power (W or kW)
- VL — line-to-line voltage (V)
- IL — line current (A)
- cos φ — power factor (0–1)
- η — motor efficiency (0–1)
Power Triangle
Where S is apparent power (kVA), P is active power (kW), and Q is reactive power (kVAR).
Practical Example
Given: P = 15 kW, V = 400 V, cos φ = 0.85, η = 0.91
I = P / (√3 × V × cos φ × η) = 15000 / (1.732 × 400 × 0.85 × 0.91) = 28.0 A
S = √3 × V × I = 1.732 × 400 × 28.0 = 19.40 kVA
Q = √(S² − P²) = √(19.40² − 15²) = 12.30 kVAR
💡 Tip: When calculating electrical input power from a motor’s rated mechanical output, always divide by efficiency η. The nameplate kW is typically the shaft (mechanical) output.
Professional field balancing instruments and software. Used in 50+ countries.
A reliable **three phase motor power calculator** is an essential tool for electrical engineers and technicians who need to quickly determine active, apparent, and reactive power values without performing manual computations. By inputting known parameters such as line voltage, line current, power factor, and efficiency, this three phase motor power calculator applies the standard formula P = √3 × V × I × cos φ × η to deliver accurate results in seconds. Its bidirectional functionality allows you to solve for any unknown variable, making it invaluable for motor sizing, load analysis, and energy auditing tasks.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
