Servo Motor Sizing Calculator

Choosing the right servo motor for a motion application requires matching the motor's torque and power ratings to your actual load — the Servo Motor Sizing Calculator does that math for you. Enter your load inertia, operating speed, angular acceleration, load torque, duty cycle, and safety factor to calculate the Required Motor Torque and Required Power. Secondary outputs include angular velocity, torque with safety factor applied, and a recommended motor size category.

kg⋅m²

Total inertia of the load as seen by the motor

rpm

Maximum operating speed required

rad/s²

Required angular acceleration rate

N⋅m

Continuous torque required to overcome load resistance

%

Percentage of time motor operates at full load

Safety margin for reliable operation

Results

Required Motor Torque

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Angular Velocity

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Required Power

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Torque with Safety Factor

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Recommended Motor Size

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Frequently Asked Questions

What safety factor should I use for servo motor sizing?

Use 1.25 for standard applications, 1.5 for heavy duty or high-precision requirements, and 2.0 for extreme conditions with frequent starts/stops or harsh environments.

How does gear reduction affect servo motor sizing calculations?

Gear reduction reduces the required motor torque by the gear ratio but increases the reflected load inertia by the square of the gear ratio. This affects both torque and acceleration calculations.

What's the difference between peak torque and continuous torque ratings?

Peak torque is the maximum torque a motor can produce for short periods (acceleration), while continuous torque is what it can sustain indefinitely without overheating. Size based on continuous requirements.

How do I calculate load inertia for complex mechanical systems?

For rotating loads, use J = mr² where m is mass and r is radius. For linear systems, reflect the inertia through the drive mechanism. Complex assemblies require summing individual component inertias.

Why is duty cycle important in servo motor sizing?

Duty cycle affects thermal management and continuous torque capacity. Motors can handle higher torques for shorter duty cycles due to thermal time constants and heat dissipation capabilities.

What motor size standards should I consider?

Common servo motor frame sizes include NEMA 17, 23, 34 for smaller applications, and larger industrial sizes. Consider mounting compatibility, shaft size, and electrical interface requirements.

How do I account for friction and load variations?

Include all friction forces in your load torque calculation. For varying loads, use the RMS (root mean square) value or worst-case scenario, depending on application criticality.