Inverters.. 2

[powerjunx]

hi folks!!

Variable Speed/freq. drives, Inverters..
What are the difference between:
1.) Sensorless Vector.
2.) Flux Vector.
3.) V/F.
why it was called so?How it affects the system(Drive)itself?

i would appreciate any additional suggestions.

 

[GusD]

Hello fbjavier

Sensorless Vector Drive would be a Drive operating without a speed feedback (Encoder/Tacho).

New VFDs have the capability of providing a form of DTC(Direct Torque Control)without the benefit of actual speed feedback. Microprocessing capabilities allows the system to operate like a Flux Vector with actual speed feed back.
As for the name Flux Vector or Vector drive,I don't think there is a difference in the names.Th Flux Vector has the
ability to continously magnitize the motor and be ready to deliver Full Torque at near (0)zero angular displacement.The F/V drive behaves much like a DC motor insofar as Torque and Speed control are concerned.Most of the applications using FVector drive capability, are of the Constant Torque type of loads.These Drives are able to deliver precise Full Torque control at near Zero speed.On Variable Torque applications this is not as much of a concern.
In the past we had to provide accurate speed feedback to
run a F/V,the newer drives are able to do the same without anactual speed feedback.
There are many Web sites with great info on all types of drives and what makes them work.Try ABB,ALSTOM,CEGELEC ,AB or a start.

GusD

 

[avigodner]

For true Vector, one has to accurately determine rotor position for permanent magnet motor or flux position for induction motor to apply optimal stator current. In the absence of position sensor (encoder / resolver) which is (position) sensorless control, motor math model along with state observers, Kalman filters etc are used for rotor / flux position estimation. Model based control is typically sensitive to motor parameter variation (resistance temperature dependence). Hence the need for on-line parameters adaptation.

Position detection at very low (zero) speed is based on other physical phenomena like magnetic saliency.

For permanent magnet brushless motor, good DC (trapez) position sensorless control may be better than poor Vector (sine) one.

Some more sensorless info can be found at

http://www.drbrushless.com/cgi-bin/articles.phtml

 

[Warni]

@avigodner

Thanks for the Info but you have to pay for the Info's !

Regards

 

[jbartos]

Suggestion: Reference:
1. Bimal K. Bose "Modern Power Electronics and AC Drives," Prentice Hall PTR, 2002,
Page 388 Section 8.5 Sensorless Vector Control:
... A speed signal is required in indirect vector control in the whole speed range and in direct vector control for the low-speed range, including the zero speed start-up operation.
Reference 1 covers the AC drives such a way that an engineer, designer, educator, student and enthusiast will find it very informative. It has many 5 star reviews.

 

[GGOSS]

Hello fbjavier,

See paper by Frank J Bartos, Executive Editor - Control Engineeering at:

http://www.manufacturing.net/ctl/index.asp?layout=article&articleid=CA188258&pubdate=11/1/2001

Regards,
GGOSS