Quote:
Originally Posted by Joel J.
Where did you get these numbers? You tested the motor?
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No, they are a purely theoretical APPROXIMATION based on the Kt, Kv and stall current posted on the bane-bots website.
They are based on a model which works pretty well for DC motors in which torque is porportional to current and back emf is porportional to motor rpm. This model does not take into account inductive effects or internal bearing resistance of the motor.
Kt is a constant of porportionality relating motor output torque to electrical current input.
Kv is a constant which relates the rotational speed of the shaft to the voltage generated by the motor.
torque = I*Kt
Induced back emf(voltage created by the motor) = shaft speed * Kv
r= internal resistance of the motor = supply voltage/stall current.
combine these three and you get
torque = Kt*(Vin-Kv*rpm)/r
then for mechanical power in a rotating system we have
power = speed * torque
so
power = rpm*Kt(Vin-Kv*rpm)/r
sorry ,that was a Terrible explanation, but its 3:29 am and i'm tired.