Assuming a motor model from the equation T = J.(dw/dt) + B.w

where J = Inertia; T = Net Torque; w = angular speed, t = time, and B = damping factor.

Q1. What does the damping factor actually depend on physically?

Assume the rotor has inertia Jr, If I somehow extend the rotor shaft by coupling it to a cylindrical object of inertia Je (assume the axis is coincident with the rotor axis of rotation for simplicity), I think that in the equation above, J would become J = Jr + Je. This leads to the last 2 questions:

Q2. Is my thinking right?

Q3. Will this have any effect on B?

Cheers!

 

> Q1. What does the damping factor actually depend on physically?

B would be the electrical load on the machine (generator).

> Q2. Is my thinking right?

Yes, summing to two inertia will give you the combined inertia

> Q3. Will this have any effect on B?

No, the electrical load (B) is independent of the mechanical inertia (J)

 

Hi Dapo,

There will be an effect in electrical load, if you increase the net torque...because in generating action, the torque produced from the rotor side will be converter to amps in stator side....

Example: for synchronous generator with 3000 rated rpm....if you increase the torque from standstil, speed will go from 0 to 3000 rpm. if you increase the torque further, this additional torque will get converted to amps, i.e.Generator current. For motoring action, just opposite, current will get converted to amps.