Then the loss of power at 1000RPM (consistent with the above example) attributed to the friction/churning is 24W- 1W= 23 W =23/746*550=17 ft-lb/sec. You could get a handle on this by running the system at the design speed and from its inefficiency determine the loss of power after subtracting IR losses.Īs a simple example, suppose we have a DC motor at 24V putting out 1 amp of power under no load and having an armature resistance of 1 ohm. The main torque would be to accomodate friction and churning. 03 in-oz sec^2, then the torque due to motion for 10 seconds would be: For example if it takes 10 seconds and the acceleration is constant and the speed at the turning point is ramps up to 10 RPM, then the acc=10/10*2*pi/60=0.1 radian/sec^2.įurther, if the gear ratio is 100:1 and the motor inertia is. Irefl=Imotor*(n)^2 or the inertia of the motor x fwd gear ratio squared. Usually the inertia at the motor shaft would be the predominant inertia and its reflected value would be : In the absence of friction and churning, the backdrive torque is only a function of the reflected inertia and the time it takes to come to speed so that you can determine its acceleration.
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