← Motor Engineering Knowledge Library
A single torque figure is incomplete. State when the torque is needed, at what speed, for how long and under which supply and cooling conditions. Starting, peak and continuous requirements can lead to different motor and controller choices.
Define each torque requirement
| Term | Question to answer |
|---|---|
| Starting torque | Can the system overcome the initial load and begin accelerating? |
| Peak torque | What temporary demand occurs, at what speed, for how long and how often? |
| Continuous torque | What torque can be sustained under the stated thermal and operating conditions? |
| Stall or limiting torque | How does this particular supplier and motor family define the term? |
Terminology varies. In a DC motor data sheet, stall torque commonly refers to zero shaft speed at a stated supply or current condition. Some AC-motor references use stall or maximum torque to describe a limit on the running characteristic. Read the definition and curve rather than assuming two catalog labels mean the same thing.
Acceleration is part of the load
At a simple rotating shaft, the acceleration component is T = J × α. It must be considered together with process torque, friction and transmission effects. For an illustrative inertia of 0.001 kg·m² and acceleration of 100 rad/s², the acceleration component is 0.10 N·m. This calculation excludes friction and process load and is not a Zhanye motor specification.
For a gearbox, distinguish motor-shaft and output-shaft quantities. Gear ratio, efficiency, permissible gearbox torque and reflected inertia affect the complete-system requirement.
Why peak output is not a continuous rating
A short demanding event may be thermally different from repeated events with insufficient recovery time. Current limiting, winding temperature, bearings, transmission components and electronics can each constrain the usable peak. A catalog maximum measured at one operating point is not permission to use that point continuously.
Write a load profile instead of one number
- Describe breakaway load and the starting position.
- State target running speed and normal process torque together.
- Record the peak’s magnitude, duration, repetition and recovery time.
- Include direction changes, braking and load variation where relevant.
- Specify supply tolerance, enclosure, ambient conditions and cooling.
A time trace from the real mechanism is useful. If measurement is not available, separate estimates from confirmed requirements and agree how prototypes will resolve the unknowns.
Validate the motor and control system together
Confirm acceleration, loaded speed, current and temperature in the intended mechanism. Observe protection response and recovery behavior under the agreed test plan. Do not use a stall test as a routine way to discover an unknown continuous rating.
Related: performance-table interpretation and five motor types. Share the load profile before asking for a model shortlist.
Request an Engineering ReviewSTART YOUR MOTOR PROJECT
Talk with Our Motor Engineering Team
Share your application, operating point, mechanical envelope and estimated quantity. We will help compare available motor platforms and identify the next engineering step.
Helpful information to include: target voltage, speed, torque, duty cycle, available dimensions, project stage and estimated annual demand.