Motor Full-Load Current Calculator
Estimate the full-load current of a three-phase motor from its shaft power, efficiency and power factor.
Results
Current
20.29
A
Active power
12.088
kW
Apparent power
14.056
kVA
What this tool does
A motor's nameplate power is the mechanical output at the shaft; the electrical input is larger by the efficiency. This calculator works backwards from shaft power to the current the supply actually has to deliver, which is the figure that sizes the cable and the protection.
Formula
I = P ÷ (√3 × U × cos φ × η)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
p | Power | kW |
u | Line-to-line voltage | V |
pf | Power factor | — |
ef | Efficiency | % |
I | Current | A |
Pin | Active power | kW |
S | Apparent power | kVA |
Worked example
- Power11 kW
- Line-to-line voltage400 V
- Power factor0.86
- Efficiency91 %
- Current20.29 A
- Active power12.088 kW
- Apparent power14.056 kVA
Limitations
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.