Thread: Discussion Motor formulas View Single Post
 Feb 01, 2009, 09:46 AM Impossible? Hah! Oslo Fornebu, Norway Joined Jun 2003 3,074 Posts Hey! I just realized there is a formula missing. Kt = T * L * D^2 Where T is a torque-constant for the motor reliant mostly on the magnet strength and airgap. L is the length of the stator stack and D is the diameter of the stack. There is another Kt formula based on the actual values instead of just a constant. Kt = 1/Kv but depending on the Kv units it may become: Kt = 60/(2*pi*Kv) This turns a rpm/volts Kv into a radians/second/volts so that Kt becomes Nm/A. An interesting thing about the first formula is it shows that, as mentioned, The relationship between Kt and Kv is inverse proportional and that length of stack has a linear relationship with Kt and Kv. What it also shows is that the diameter has a squared relationship! This is important if you need more torque. For a in-wheel motor, maximizing diameter will increase torque by D^2 while increasing width only adds L.