vfd voltage dip compensation

[powerjunx]

Just wanna know how VDF voltage dip compensates to provide uninterruptible motor operation?
Thanks..


"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.

 

[Marke]

Hello billybry

By decelerating the motor, energy from the driven load can be transferred back into the DC bus in a manner to keep the drive electronics operating.

When the DC bus volts begin to fall too low, the load is decelerated at a rate to keep the volts up. When the supply volts return to the correct value, the drive can speed back up to its correct speed.

Best regards

Mark Empson

http://www.lmphotonics.com

 

[Skogsgurra]

To elaborate on Mark's post: Obviously, it doesn't always work. But loads with large inertia and moderate friction running near rated speed can survive rather long dips. Large centrifugal fans, for instance, can keep up tens of seconds while a screw type pump working against a head usually can't provide energy for more than about 100 milliseconds - or even less.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[powerjunx]

Marke, Skogs.. thanks for your reply. I got your point!

In actual scenario, my colleague never experience such voltage dip as we expected to dealt with but rather a voltage fluctuation.
We've been always got stucked on generation unit tripping due to this fluctuation where motor pumps (centrifugal) tends to be interrupted whenever such disturbance occurs.
Noting that pump control unit is electromechanical direct on-line control, we want to resolve the issue to tackle such tripping as to phase out conventional control on pump while replaced it with VFD or SoftStart whichever is highly recommended to overcome such voltage fluctuation.
So my query then emerge on this issue:
How VFD or S/S compensates such annoying voltage fluctuation that obviously resolves our tripping issue? Any thoughts about auto-start of VFD or S/S or any feature pertaining to resolve fluctuation and other disturbances?

Thanks again.

bill




"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.

 

[LionelHutz]

Maybe define your voltage fluctuation. How much and how long do you want to compensate for?

 

[powerjunx]

lionelhutz, a fluctuation that is "enough to release the magnetic contactor" as a short time voltage loss for our direct on-line lube oil motor pump control.
Sorry to tell you about the definite time but the scenario well , i think, gives you the detail.

"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.

 

[Skogsgurra]

So, what you are asking is actually "Can a VFD or a softstarter override a voltage dip?".

Yes. VFDs can, mostly, but some have quite sensitive mains loss detection, so there you are again. Luckily (or perhaps by design ) it is possible to kill the mains supervision and also activate the "kinetic buffering" as one supplier calls it. If your plant can survive a stop and automatic restart, that's also a possibility in most drives.

Softstarters can not utilize the kinetic energy in the load to keep things going. A softstarter is mostly (always) disconnected after a start, so your only option there is an automatic re-start.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[powerjunx]

skogs, i'm quite confuse.
To clear it up, as i understood, though VFD keen to voltage loss (fluctuation) a configuration or setting is preferred to be made in VFD itself to override this disturbances. One is to disable voltage loss detection and the other is to enable kinetic buffering.
Doing this configuration, does this two settings are dependent to each other? About kinetic buffering, is it similar to "catch spinning" VFD feature?


"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.

 

[Marke]

Hello billybry

It is difficult to give a generic answer with VFDs as they are all different. It is possible to design VFDs that will provide a high level of voltage dip ride through and some do this very well. Others will trip very quickly on a voltage dip, so it comes down to ensuring that you use a VFD that will provide the performance. Do not rely on all VFDs doing so, because some will not.

Soft starters can not provide the ride through, but some will provide a better level of control under low voltage than others. If the supply reduces significantly, then the motor will begin to stall, or the flux will significantly reduce with a reclose transient when the voltage returns to normal.
Once again, some soft starters lose control at a relatively small voltage sag, and others have a much greater margin.

Loss of power for a few cycles could be handled OK with some VFDs, but not soft starters. A droop in supply voltage to 50% for a few cycles can be handled by some soft starters but not all.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[powerjunx]

thanks marke! With your sensible comment and so to speak expert to this field can you give me VFD OEM that somehow might satisfied to my query. We're planning at this time to purchase SIEMENS or ABB VFD, but our technical personnel were hesitant about such feature regarding fluctuations.

regards
bill






"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.

 

[Skogsgurra]

No "catch spinning" is not "kinetic buffering".

The "kinetic buffering" is what Mark and myself described in our first answers.

"Catch spinning" comes later - when the drive already has tripped an you need to start before the running load has come to a standstill. That is also called "flying start" by some suppliers.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[DickDV]

The ABB drives have the ability to provide "power outage ride through" as they call it. You will find the parameter to turn it on and off at Group 20 Parameter 20.06 (Undervoltage Control)

It doesn't matter what ABB drive model you have. They all have the same software structure and parameter numbering system.

 

[powerjunx]

Skogs,thanks.. i got your point the aforementioned above post is indeed what you brought up to explain about kinetic buffering. And catch spinning is likewise distinct feature for VFD aside from kinetic buffering.
Marke, "By decelerating the motor, energy from the driven load can be transferred back into the DC bus in a manner to keep the drive electronics operating." Do this mean a "regenerative action" produce by the deccelerating motor? I guess this is not common to all VDF OEM's, am right?
Somehow this buffering action might not work on specific application like our vertical split case centrifugal pump where a considerable head of lifting the lube is quite heavy and lengthy, thus Skogs is right.. and prettty it works with fans and blower applications.
DickDV has good points here, i think this also address my query. Disabling/Enabling power loss feature or so called
"power outage ride through" of ABB. But i'm hesitant about this since it's in the undervoltage control setting, i'm thinking of configuring this override only at a certain extent of reduce percent voltage below the rated voltage as it seems VFD power up by low voltage while not overriding the real culprit - a sudden voltage loss. Any good thoughts?
Thanks, guys.

Regards,
bill








"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.