Calculating Brushless Motor's Torque

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    Brushless Torque
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SUMMARY

The torque of a brushless DC motor, particularly out-runners, is primarily determined by the motor constant, which is specified in the motor's datasheet. This constant indicates the direct proportionality between the average torque developed and the armature current supplied. The torque can be expressed using the formula T=NIABSinΘ, where N represents the number of turns, I is the current, A is the area of the loop, B is the magnetic field strength, and Θ is the angle between the magnetic field and the current. Measuring the torque directly is often more practical than calculating it based on theoretical parameters.

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  • Understanding of brushless DC motor design and operation
  • Familiarity with torque calculations and the physics of electromagnetism
  • Knowledge of motor constants and their significance in performance
  • Ability to interpret motor datasheets for specifications
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  • Research the torque constant of specific brushless DC motors
  • Learn how to measure torque in brushless motors using appropriate tools
  • Explore the impact of magnetic field strength on motor performance
  • Study the relationship between armature current and torque in electric motors
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Engineers, hobbyists, and researchers involved in electric motor design, robotics, and automation who need to understand and calculate the torque of brushless motors.

iamdenis
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Hello,

I was wondering if anyone knows about calculating the torque of a brush less motor (preferably an out-runner).

Is there a way to get the torque based on resistance, number of turns, and number of poles?

Thank you,
Denis
 
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An analytical expression for the instantaneous torque developed by some brushless DC motor is somewhat complicated and it will probably not be very helpful to you.

What usually matters in the case of brushless DC motors is that they're designed in such a way that the average torque they develop (over an electrical cycle) is directly proportional to the armature current you supply them with. This torque/current proportionality constant is commonly called the torque (or motor) constant and is usually specificed in the datasheet of the motor.
 
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Do you remember from your basic physics the torque on a loop in a magnetic field?
T=NIABSin\Theta


So the torque includes in addition to the things you mentioned magnet strength and geometry.

I'd wager it would be easier to measure than to calculate.

Or as Miles suggested - look up its datasheet.
 
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