Why account for gear ratio in torque estimation?

• A. To account for mechanical advantage affecting torque and speed.
• B. It only affects color of cables.
• C. It has no effect on torque.
• D. It determines the maximum voltage.

Answer: (A)

Gears provide mechanical advantage, trading torque for speed. The gear ratio tells you how the motor’s output is transformed on the load side. In a gear train, a higher reduction ratio increases the torque at the output while reducing the angular speed, roughly by the same factor (and minus some efficiency losses). So, to estimate the torque that the load actually experiences, you multiply the motor torque by the gear ratio and factor in efficiency. If you didn’t account for this, you’d misestimate the load torque because the gears are amplifying or reducing it.

For example, a 3:1 reduction means the output torque is about three times the motor torque (minus losses) and the output speed is one-third the motor speed. The other options aren’t relevant: cable color has no impact on torque, gear ratio does affect torque, and it does not determine the maximum voltage.