Power of the electric motor is related to its torque and shaft speed according to the following formula:

P = M x w

P is power of the motor in Watts (W)

M is torque on the motor shaft in Newton meters (Nm)

w is angular speed of the motor shaft in radians per second (rad/s)

In order to convert motor speed from revolutions per minute(RPM) to radians per second(rad/s)use the following formula:

rad/s = [60/(2 x 3.14)] x RPM

For example: 1500 RPM = [60/(2 x 3.14)] x 1500 = 14331.2 rad/s

If rated power of the motor is 7.5kW and its rated speed is 1500RPM, its shaft torque is:

M = 7500 / {[60/(2 x 3.14)] x 1500} = 7500 / 14331.2 = 0.523 Nm