Dec 192011

Torque is the third in the trio of tools, along with inertia and speed, which I need to work with to calculate the right size of servomotor for a project.

When picturing Torque I like the analogy of the cyclists approaching a hill. The force delivered at the pedals to propel a cyclist up the hill will be the same regardless of the speed. The cycle’s gearing mitigates the steepness of the hill. Equally, if a motor requires 10 amps to spin it up, it will still need 10 amps regardless of whether it runs at 2000 or 10000 rpm.

In practice, motors usually have a higher speed and lower torque than required and it is the gearing, the subject of a future blog, which bridges the gap.

Once Speed and Torque have been selected and the motor identified I can then use that to establish real values and provide an absolute check that the right selection has been made. I must not forget that load and motor inertia need to be added together and then add a % safety margin.

This then leads to consideration of electrical needs, the working environment, heat dissipation and so forth, which will be the topics of blogs to come.

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