Engineering purpose
Use the sequence below to establish a defensible starting point, then confirm the decision with model-specific performance, tolerances and test evidence.
Begin with the Driven Function
Describe what the equipment must move, how it moves and what successful operation means. Avoid beginning with an existing motor part number unless replacement interchangeability is itself a fixed requirement.
Quantify Performance and Duty
Define speed, continuous and peak torque, acceleration, positioning, reversals, holding and the complete repeating cycle.
- Worst-case load and friction
- Normal and maximum operating speed
- Emergency, jam and stall conditions
Define Electrical and Control Boundaries
State the available supply, voltage tolerance, current capability, controller arrangement, feedback, communication and braking or regeneration requirements.
Capture Mechanical and Environmental Interfaces
Envelope, mounting, shaft loads, orientation, temperature, ingress exposure, vibration, acoustic limits and service access can eliminate otherwise suitable technologies.
Establish Validation and Production Objectives
Agree measurable prototype acceptance criteria, documentation, anticipated volumes, target life, change control and regulatory destination before detailed development.
Worked example
Convert a conveyor statement into engineering inputs
Given
- Move 25 kg at 0.4 m/s
- Drive roller radius: 50 mm
- Estimated tangential resistance: 120 N
- Acceleration time: 0.5 s
Method
- Roller speed = v/r = 0.4/0.05 = 8 rad/s, approximately 76 rpm.
- Steady roller torque = F×r = 120×0.05 = 6 N·m.
- Add acceleration, transmission losses, service conditions and starting margin before selecting motor and ratio.
Engineering result: The usable requirement begins at approximately 76 rpm and 6 N·m at the roller—not at a guessed motor wattage.
Common mistakes
What to Avoid
- Starting from a preferred technology
- Using average load instead of the worst credible cycle
- Omitting voltage tolerance and current limits
- Leaving acceptance criteria until prototype testing
Selection check
Confirm Before Selection
- Function, load and motion profile
- Supply, control and feedback
- Envelope, shaft and mounting
- Environment, life, compliance and production volume
SDT engineering note
Apply General Knowledge with Product-Specific Evidence
This guide supports preliminary engineering. Final selection must be confirmed against the complete application, selected motor and drive data, declared operating conditions, applicable standards and agreed validation criteria.