Torque Calculation for Electric Motor Current

Torque Formula (3-Phase Motor):

\[ Torque = \frac{Current \times Voltage \times Efficiency \times 9550}{RPM \times \sqrt{3} \times Power\ Factor} \]

Current (I):

Voltage (V):

Efficiency (η):

(0-1)

RPM:

rev/min

Power Factor:

(0-1)

Torque:

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1. What is Motor Torque Calculation?

The torque calculation for electric motors determines the rotational force produced by a 3-phase AC motor based on its electrical characteristics and operating conditions. This is essential for motor selection, performance analysis, and mechanical design.

2. How Does the Calculator Work?

The calculator uses the torque formula for 3-phase motors:

\[ Torque = \frac{Current \times Voltage \times Efficiency \times 9550}{RPM \times \sqrt{3} \times Power\ Factor} \]

Where:

\( Current \) — Motor current in amperes (A)
\( Voltage \) — Line voltage in volts (V)
\( Efficiency \) — Motor efficiency (0-1)
\( RPM \) — Rotational speed in revolutions per minute
\( Power\ Factor \) — Ratio of real power to apparent power (0-1)
9550 — Conversion constant (derived from 60,000/2π)

Explanation: The formula accounts for the electrical power input, motor efficiency, and converts it to mechanical torque output considering the motor's speed.

3. Importance of Torque Calculation

Details: Accurate torque calculation is crucial for proper motor sizing, ensuring the motor can handle the mechanical load, preventing overheating, and optimizing energy efficiency.

4. Using the Calculator

Tips: Enter current in amps, voltage in volts, efficiency (typically 0.8-0.95), RPM, and power factor (typically 0.8-0.95). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is 9550 used in the formula?
A: 9550 is the conversion factor from watts to Nm when using RPM (60,000/2π ≈ 9550).

Q2: What's a typical power factor for motors?
A: Most AC motors have power factors between 0.80-0.95 at full load, lower at partial loads.

Q3: How does torque vary with speed?
A: For AC induction motors, torque is highest at zero speed (starting torque) and decreases as speed increases.

Q4: What affects motor efficiency?
A: Efficiency depends on motor design, load, quality of materials, and operating temperature.

Q5: Can this be used for single-phase motors?
A: No, this formula is specifically for 3-phase motors. Single-phase motors require different calculations.