VFD data fluctuation

[Lenz81]

Hello guys

My VFD output Voltage, Current and frequency are fluctuating (what i show on VFD LCD), is that normal ? if not what can be the reason?any thing i can do?

thanks in Advance.

 

[dpc]

Amount of fluctuation? VFD size/manufacturer? Motor running OK? Is this with door open or closed?

VFDs are powerful sources of RFI - if the VFD is not properly grounded and any factory-provided shielding in place, low-level signals can easily be disrupted.

"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[jraef]

It also depends on the programming of the VFD. If for instance it is programmed as a torque follower or for torque control, voltage, speed and current will be dancing all over the place to maintain a specific torque on a varying load profile.

You need more information on what is happening and what is supposed to be happening.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[Lenz81]

thanx gentelmen

Dpc ,motor is running pretty good ,The VFD is GE AV300 i ,and that is with door closed.
Jraef you are right it is programmed as torque follower , can this fluctuation damage the VFD in long term ?

 

[Skogsgurra]

No. Not at all. Not as long as operation is within motor and VFD specs.
Only situation is if the speed varies down to speeds where cooling is reduced. Is there an external cooling fan that works independent of motor speed?

Gunnar Englund

http://www.gke.org

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

 

[jraef]

Methinks Skogs is referring to possible motor damage at low speeds, not VFD damage. But other than that he's right, no VFD damage, they are made to do that. The fluctuations you are seeing are to be expected and perfectly normal for a torque follower application.

In other words, you hired it to d a job, it's doing it, just pay no attention to that man behind the curtain.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[Skogsgurra]

Yes Jeff. Was thinking of the motor being overheated at low speeds. Not the VFD.

BTW - is there a man behind the curtain? Never thought of it that way...

Gunnar Englund

http://www.gke.org

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

 

[jraef]

He's really tiny, they call him "The Wizard of Hz"

He loos a lot like you actually...

 

[jraef]

Damned keyboard...

 

[Lenz81]

Thanks guys for help , for low speeds I have not seen anything wrong up to now, it is a 125Hp motor which is running a fan ,my temp reading are pretty good for 4 hours test run.

 

[Skogsgurra]

Good-looking then?

Gunnar Englund

http://www.gke.org

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

 

[Lenz81]

YES GOOD LOOKING , THANX

 

[jraef]

Torque follower on a fan???


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[Lenz81]

yes Jraef , it has been set up by manufacturer ,anything wrong with that?

 

[itsmoked]

Yes it's weird. Why would you set up a fan to run at rapidly varying speed? While torque control is a perfectly fine function why would you want a fan rapidly changing speed continuously? Especially a 125hp fan. The air is not going to change speed rapidly. This just results in more wear and tear on the motor, blades, hub, belts, and the VFD.

What, exactly, is the fan doing?

Keith Cress
kcress -

http://www.flaminsystems.com