Starting Torque of a Brushless DC engine 1

[hyboxis79]

Is there anyway of predicting what will be the starting torque of a BLDC motor (BRUSHLESS DC MOTOR) without asking the manufacturer?

Can I know the starting torque by consulting the manufacturer of the BLDC motor controller?

 

[hyboxis79]

I've noticed somebody calculating the starting torque by the equation


T_stall= K_torque*(V_nominal/R_armature)

Does that mean the motor has to overcome the large amount of current it has at the beginnig

can anyone elaborate?

thanks

 

[cswilson]

The fundamental torque equation is

T = Kt*I

The fundamental voltage equation (steady state) is

V = Ke*w + R*I

At zero speed (stall), the Ke*w term goes away, so

I = V/R

and

T = Kt*V/R

This is presuming that the motor can handle all this current. I have generally found that motors rated for under, say, 48V can handle full voltage at zero speed. However, motors designed to run off rectified 120V or higher generally cannot. If you apply full bus voltage to one of these motors at rest for even a few milliseconds, you will likely end up with a nice door stop.

Curt Wilson
Delta Tau Data Systems