Servo selection is not a power-rating exercise. A motor with higher wattage can still vibrate, overshoot or alarm if the inertia ratio, acceleration profile or mechanical transmission is unsuitable. Before choosing a servo drive and motor, collect the motion data that actually defines the load.
Power is only one result
Rated power is calculated from speed and torque demand, but the machine does not care about the label first. It cares about load mass, friction, acceleration, deceleration, vertical holding, cycle time and mechanical stiffness. Treat power as the result of sizing, not the starting point.
Inertia affects control quality
A large mismatch between motor inertia and load inertia can make tuning difficult. The acceptable range depends on mechanism, drive capability and performance requirement. If the machine needs rapid positioning, stable stop and low vibration, inertia data becomes especially important.
Collect mechanical details
For a screw axis, record screw pitch, moving mass, coupling, guide friction, target speed and acceleration time. For belt or pulley systems, record pulley diameter, load mass and gear ratio. For rotary loads, record load inertia or geometry if available. Photos of the mechanism are often useful.
Brake and vertical axis checks
Vertical axes, lifting mechanisms and inclined loads may require a brake, holding torque review and safety consideration. Do not replace a servo motor without checking whether the brake voltage, wiring and control sequence match the machine requirement.
Quotation information
Send axis function, load type, stroke, speed, acceleration, existing motor and drive model, encoder type, brake requirement and control protocol. This allows a supplier to recommend a servo family with fewer assumptions.
Common mistakes to avoid
The most dangerous shortcut is replacing a servo by wattage alone. A larger motor can increase inertia, change tuning behavior and create new vibration. A smaller motor may run hot or alarm under acceleration. Mechanical data is the difference between a guess and a recommendation.
Practical buyer note
If exact inertia is not known, provide mechanism photos and basic dimensions. A supplier can often identify whether the application is a ball screw axis, belt axis, rotary table, winding axis or vertical lifting axis and ask the next useful questions.
Quick checklist
- Load mass or inertia
- Stroke, speed and acceleration
- Transmission type and ratio
- Brake requirement
- Encoder and feedback type
- Control mode and bus protocol
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