VFD Motor Parameter Auto-Identification

Hey guys,

I was wondering if anyone could shed some light on what actually happens during the stationary and rotational motor parameter auto-identification that takes place when commissioning drives. The Siemens G120 units I've been working with apply something like 20V on and off to the motor (1hp, 400V) in stationary mode, then run it at around 1500 rpm for around 30 secs with 3-4 quick accelerations in the rotational ID mode. What parameters specifically is the drive measuring during each of these processes?

I believe that in sensorless vector mode, the drive does both the stationary measurements and the rotational measurements when I select them both, but if I remember correctly, I thought in V/hz mode it only did the static measurement. Does this make sense?

Finally, should the motor always be decoupled from the load during this process? Or connected to it (assuming no damage can be done)?

Thanks!

The purpose of the motor ID run is to allow the VFD to create a motor model in its memory that it can consult for % of nameplate torque and motor shaft speed. To determine shaft speed, a good motor model will need to know exactly how much slip occurs for each ft-lb or torque in the shaft, the motor rotor inertia, as well as correct motor nameplate data. Without this model, the VFD sensorless vector performance would be worse than if you had left it in V/hz mode