I want to make brushless motor.

[balraj]

Sir, I want to make a brushless motor out runner type. Body is 2.5 thick with 25 cm outer dia. It's weight is 25kg. Shaft of stator is 4cm in dia. How much watt is required for rotating this outer body at speed of 12000 rpms.

 

[David Lewis]

How much torque would you like the motor to produce?

 

[jim hardy]

Of what material will that "out runner" be made? Have you checked it has tensile strength to stay together at 12,000 RPM and 25 cm OD ?

 

[CWatters]

The load will normally determine the power drawn. If it doesn't then the motor probably isn't very efficient.

The no load power will depend on losses in the motor and these are hard to calculate. They include losses due to winding resistance, eddy currents and air drag.