View Single Post
  #12   Spotlight this post!  
Unread 21-05-2014, 16:36
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,149
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: motor Ke and Kt Quiz

Quote:
Originally Posted by Paul Copioli View Post
at high current (aka, near stall), the magnetic field saturates producing less actual torque than ideal...However, it is not the only difference.
Thanks Paul. I think that completes the explanation.

"Kt equals Ke" is a theoretical result which is only approximately true for real-world motors.

Firstly, the "linearity" (straight lines) assumption (notice the asterisks) used to compute Kt would not be valid when the magnetic field saturates.

Second, "other_losses" such as bearing friction, windage & viscous damping, eddy currents, and hysteresis in the power equation account for the difference between Ke and Kt.