On Sat, 14 Jun 2008 05:45:19 -0500, "RogerN"
wrote:

We are running equipment at work that have Siemens MicroMaster drives. In
some cases we need speed settings below 5% (below 3hz) and are having
difficulty getting good torque and speed control. I noticed these drives
have a setting to enable sensorless vector control. I was wondering if
anyone here has experience with using sensorless vector control on drives
and if you think it would give us good speed control at low speeds?

Thanks!

Roger N

Sensorless vector gives better speed regulation than Volts-Hertz, but
less than 3 Hz is too slow for good torque with an induction motor.
Sounds like you need a servo motor or if this is continuously low
speed consider a gear reducer.

My first drive was flux vector on a 50 Hp. drive (closed loop speed
feedback). That gave pretty good low speed torque, which was required
in the application (extruder), but I sure didn't operate all the time
at low speed.

Pete Keillor