Calculator Inputs
The overall page uses a single-column layout. The calculator fields use a responsive 3-column, 2-column, and 1-column grid.
Example Data Table
| Example | Motor Type | Voltage | Rated Power | Load | Running Current | Torque | Annual Energy |
|---|---|---|---|---|---|---|---|
| 1 | Three Phase AC | 415 V | 7.50 kW | 70% | 9.77 A | 34.82 Nm | 11,231.46 kWh |
| 2 | Single Phase AC | 230 V | 3.73 kW | 78% | 16.16 A | 16.11 Nm | 4,222.01 kWh |
| 3 | DC Motor | 220 V | 3.00 kW | 65% | 10.07 A | 12.42 Nm | 8,083.64 kWh |
Formula Used
1) Actual Shaft Output
Actual Output (kW) = Rated Power (kW) × Load Percentage / 100
2) Input Real Power
Input Power (kW) = Actual Output (kW) / Efficiency
3) Current for AC Motors
Three Phase Current (A) = Input Power × 1000 / (√3 × Voltage × Power Factor)
Single Phase Current (A) = Input Power × 1000 / (Voltage × Power Factor)
4) Current for DC Motors
DC Current (A) = Input Power × 1000 / Voltage
5) Apparent and Reactive Power
Apparent Power (kVA) = Input Power (kW) / Power Factor
Reactive Power (kVAr) = √(kVA² − kW²)
6) Torque
Torque (Nm) = 9550 × Output Power (kW) / Speed (RPM)
7) Annual Energy
Annual Operating Hours = Hours/Day × Days/Year × Duty Cycle
Annual Energy (kWh) = Input Power (kW) × Annual Operating Hours
8) Energy Cost
Annual Cost = Annual Energy (kWh) × Energy Rate
How to Use This Calculator
- Select the motor type: three phase, single phase, or DC.
- Choose whether the rated value is entered in kW or HP.
- Enter supply voltage, motor rating, expected load percentage, and efficiency.
- For AC motors, enter power factor. For DC motors, the tool automatically treats it as 1.00.
- Enter service factor, speed, duty cycle, daily runtime, yearly operating days, and energy rate.
- Add a starting current multiplier to estimate inrush current during startup.
- Click Calculate Motor Load to show results above the form.
- Review current, torque, demand, annual energy, and operating cost.
- Use the CSV and PDF buttons to export the detailed result table.
Frequently Asked Questions
1) What does motor load percentage mean?
Motor load percentage shows how much of the rated shaft output is being used. A 75% load means the motor is delivering three quarters of its rated mechanical power.
2) Why is input power higher than output power?
Motors are not perfectly efficient. Electrical losses in windings, iron, friction, and ventilation mean the electrical input must exceed the useful shaft output.
3) Why does power factor matter for AC motors?
Power factor affects how much current the supply must deliver for the same real power. Lower power factor usually means higher current, larger upstream equipment, and more voltage drop risk.
4) What is service factor used for?
Service factor indicates a limited overload capability under suitable conditions. It should not replace proper sizing, but it helps you judge whether the chosen operating load is too aggressive.
5) Is the starting current exact?
No. Starting current is an estimate based on a multiplier. Actual inrush depends on motor design, starter type, driven load, supply stiffness, and the starting method used.
6) Can I use HP instead of kW?
Yes. The calculator accepts either unit. When HP is selected, it converts horsepower to kilowatts internally using the standard engineering conversion.
7) Why include duty cycle in the calculation?
Duty cycle adjusts runtime-based energy use. A motor may draw full instantaneous current while running, yet consume less annual energy if it operates only part of the time.
8) Can this calculator size cables and breakers completely?
It provides a helpful feeder-current rule of thumb, but final cable, breaker, and protection sizing must follow your voltage system, code requirements, ambient conditions, and installation method.