Motor Shaft Power Calculation Formula

Motor Shaft Power Formula:

\[ P_{shaft} = \frac{Torque \times RPM}{5252} \text{ (hp)} \quad \text{or} \quad \frac{Torque \times RPM}{9550} \text{ (kW)} \]

Shaft Power (P_shaft):

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1. What is Motor Shaft Power?

Motor shaft power (P_shaft) represents the mechanical power delivered at the rotating shaft of a motor or engine. It's a crucial parameter for determining the actual work capacity of rotating machinery and is essential for proper motor selection and system design.

2. How Does the Calculator Work?

The calculator uses the shaft power formula:

\[ P_{shaft} = \frac{Torque \times RPM}{5252} \text{ (hp)} \quad \text{or} \quad \frac{Torque \times RPM}{9550} \text{ (kW)} \]

Where:

\( Torque \) — Rotational force applied (N·m or lb-ft)
\( RPM \) — Rotational speed (revolutions per minute)
\( 5252 \) — Conversion constant for horsepower calculation
\( 9550 \) — Conversion constant for kilowatt calculation

Explanation: The formula converts rotational mechanical power (torque × angular velocity) into standard power units, accounting for unit conversions and constants.

3. Importance of Shaft Power Calculation

Details: Accurate shaft power calculation is essential for motor sizing, energy efficiency analysis, mechanical system design, and ensuring equipment operates within safe power limits.

4. Using the Calculator

Tips: Enter torque in consistent units (N·m for kW calculation, lb-ft for hp calculation), RPM as positive value, and select desired power unit. All values must be valid (torque > 0, RPM > 0).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between shaft power and electrical input power?
A: Shaft power is mechanical output power, while electrical input power includes motor losses. Shaft power = Electrical power × Efficiency.

Q2: Why are there different constants for hp and kW?
A: The constants account for unit conversions: 5252 converts (lb-ft × RPM) to hp, while 9550 converts (N·m × RPM) to kW.

Q3: Can this formula be used for any rotating machinery?
A: Yes, it applies to motors, engines, turbines, and any rotating equipment where torque and RPM can be measured.

Q4: What is typical shaft power range for industrial motors?
A: Industrial motors range from fractional hp (0.5 hp) to several thousand hp, with common sizes between 1-500 hp.

Q5: How does temperature affect shaft power calculations?
A: Temperature affects motor efficiency and torque capacity, but the fundamental formula remains valid. Actual power may vary with operating conditions.