Motor Torque Calculator (Current & Resistance)

3-Phase Motor Torque Equation:

\[ Torque = \frac{Current^2 \times Resistance \times Efficiency \times 9550}{RPM \times \sqrt{3} \times Power\ Factor} \]

Current (I):

Resistance (R):

ohms

Efficiency:

(0-1)

RPM:

rev/min

Power Factor:

(0-1)

Calculated Torque:

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1. What is the Motor Torque Equation?

This calculator estimates the torque produced by a 3-phase AC motor based on current, resistance, efficiency, RPM, and power factor. The equation provides an approximate torque value useful for motor selection and performance analysis.

2. How Does the Calculator Work?

The calculator uses the 3-phase motor torque equation:

\[ Torque = \frac{Current^2 \times Resistance \times Efficiency \times 9550}{RPM \times \sqrt{3} \times Power\ Factor} \]

Where:

\( Current \) — Motor current in Amperes (A)
\( Resistance \) — Motor winding resistance in ohms (Ω)
\( Efficiency \) — Motor efficiency (0-1)
\( RPM \) — Motor speed in revolutions per minute
\( Power\ Factor \) — Ratio of real power to apparent power (0-1)
9550 — Conversion constant

Explanation: The equation accounts for the relationship between electrical power input and mechanical torque output in a 3-phase motor.

3. Importance of Torque Calculation

Details: Torque calculation is essential for motor sizing, performance evaluation, and ensuring the motor can handle the required mechanical load.

4. Using the Calculator

Tips: Enter current in Amperes, resistance in ohms, efficiency (0-1), RPM, and power factor (0-1). Typical values for efficiency and power factor are around 0.85-0.95 for most industrial motors.

5. Frequently Asked Questions (FAQ)

Q1: Why is the power factor important?
A: Power factor affects the real power available to produce torque. Lower power factors mean more current is needed for the same torque output.

Q2: What is a typical motor efficiency value?
A: Standard motors typically have 85-95% efficiency, with higher efficiency in larger motors.

Q3: How accurate is this calculation?
A: This provides an estimate. Actual torque may vary due to factors like temperature, voltage fluctuations, and motor design.

Q4: Can I use this for single-phase motors?
A: No, this equation is specifically for 3-phase motors. Single-phase motors require different calculations.

Q5: What if I don't know the resistance?
A: Resistance can often be measured with a multimeter or found in motor specifications. Alternatively, you may need to use a different torque equation that uses voltage instead.