Sensorless Vector Not An Option. Configuring V/F Control.

ptsmith · Jul 27, 2019

From my Weg CFW-08 VFD Manual:

The performance of the vector control with a switching frequency of 10 kHz is not so good as when a switching frequency of 5 kHz or 2.5 kHz is used. It is not possible to use a vector control with a switching frequency of 15 kHz.

Anything below 15KHz is like poking pencils in my ears. This is surprising because my is hearing very poor. I'm almost death in my right ear, yet 12MHz and below seems very loud even in that ear.

So unless I want a headache I have to have the carrier frequency set to 15KHz. And that means I can't use sensorless vector.

So I need to set up V/F control. Setting it up is a little more involved than sensorless vector. I could use some guidance. I screen captured that section of the manual. I appreciate any help.

mksj · Jul 27, 2019

Unfortunately 10 kHz is the max in sensorless vector, which is surprising. If you run in V/F I would start with the factory defaults and see if you get an error. Performance will be worse below around 30Hz. You can play with some of the settings torque boost to compensate P137, and slip compensation P138 a bit.

ptsmith · Jul 27, 2019

Thanks.

It actually states that 10 KHz performance isn't good either. So 10 KHz is bad and 15 KHz is not an option.

The performance of the vector control with a switching frequency of 10 kHz is not so good as when a switching frequency of 5 kHz or 2.5 kHz is used. It is not possible to use a vector control with a switching frequency of 15 kHz.

The drive defaults to V/F control. So in that mode I can play around with both P137 and P138 without harming anything?

Jraef · Jul 28, 2019

Wow, that must be a crappy drive. In most good drives, increasing the CF will IMPROVE performance in any kind of vector control; faster switching = faster response times. The bigger issue with higher CF is the increase in switching losses in the VFD, often requiring de-rating, and the exacerbation of motor winding damage and/or bearing damage.

My guess is that they are using a cheap low power chip set that can’t handle the added burden of the higher CF AND the number crunching needed for SVC. I suggest using better drives.

ptsmith · Jul 29, 2019

Actually Weg drives are on the pricey side: https://www.vfds.com/10hp-230V-weg-vfd-CFW080280TDN4A1Z I bought mine used and it's date stamped 2008. Being an old design might have something to do with it, but some of their latest models have a max switching frequency of 10KHz period. Such as the CFW11 series.

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