1. Basic Electric Motor Formulas

The fundamental formulas for electric motor power calculations vary depending on the type of current (DC or AC) and phase configuration.

Where:

• \( P \) — Power in Watts (W)
• \( V \) — Voltage in Volts (V)
• \( I \) — Current in Amperes (A)
• \( PF \) — Power Factor (0-1)

2. Motor Performance Calculations

Torque: \( \tau = \frac{P}{2\pi N} \times 60 \) (N·m)
Where \( N \) is speed in RPM

Horsepower: \( HP = \frac{P}{745.7} \)

Slip: \( s = \frac{N_s - N}{N_s} \times 100\% \)
Where \( N_s \) is synchronous speed

3. Efficiency and Power Factor

Efficiency: \( \eta = \frac{P_{out}}{P_{in}} \times 100\% \)

Power Factor: Typically 0.8-0.95 for AC motors at full load

4. Using the Calculator

Tips: Enter voltage in volts, current in amps, select phase type (DC, AC single phase, or AC three phase), and power factor (0-1). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between real power and apparent power?
A: Real power (Watts) does actual work, while apparent power (VA) is the product of voltage and current. Power factor is the ratio between them.

Q2: How does three-phase power differ from single-phase?
A: Three-phase power delivers constant power (no pulsations) and is more efficient for motors, using three conductors with 120° phase shifts.

Q3: What affects motor efficiency?
A: Factors include load percentage, design quality, operating temperature, and maintenance condition.

Q4: Why is power factor important?
A: Low PF increases current for same real power, causing higher losses and requiring larger conductors.

Q5: How to calculate motor current from power?
A: Rearrange power formulas: For three-phase, \( I = \frac{P}{\sqrt{3} \times V \times PF \times \eta} \)