# Estimate the Flux Linkage of a PMSM Motor

I'm not sure if it is possible to estimate the flux linkage of a PMSM motor (star connection) by the controller itself, where I can measure the input voltage, all the phase currents and the velocity. Measurements of R and L are also available.

The flux linkage is defined as:

$$\lambda_m = \sqrt{2/3} \frac{2}{P} K_b$$

Where P=Number of Poles and Kb theback EMF constant. So I need to come up with Kb first, but I don't know how I could achieve this. When I turn on the power supply to speed up the motor to a constant speed, I cannot measure the back EMF, because I can only measure the input voltage. Is it even possible to measure the flux linkage with this setup?

• Can't you measure back-emf by measuring the voltage over the running but (temporarily) disconnected motor? – HarryH Jun 13 at 22:30