Math Problem Solver

Following equation shows how the angular speed ωm, applied voltage u and the generated torque τm of a

DC motor are related.

τm =

Kt

R

u −

K2

t

R

ωm

where Kt and R are constants. The mechanical power output of the motor is given by

Pout = τmωm

=

Ktu

R

−

K2

t

R

ωm

ωm

A motor operated with a 9 V supply voltage has a no-load speed of 12000 rpm. It stops rotating when an

external torque of 4.2×10−3 Nm is applied. Calculate its speed and the mechanical power output when a

torque load of 10−3 Nm is applied.