Vibration of Motor Increases When Switched Over to VFD Mode

You need to EXPLAIN why the motor is USED in vfd mode in the FIRST place.

Dear Mr. Crabtree,

THANK YOU FOR YOUR RESPONSE.

Whe fan is started it draws heavy current, due to heavy GD^2 Vlue, since the fan while starting hauls the load. For VFD starting Torque is less, than DOL or STAR-DELTA starting.

Since, ID Fan having High GD^2 Value, it is started in conventional mode and run for some time till the boiler reaches full load and then SWITCHED OVER TO VFD MODE.

DHAYANANDHAN.S

YOU need TO explain WHY the MOTOR is SWITCHED to VFD mode. WHY not STAY out OF it?

VFD's in this application can cause high torsional resonance vibration at certain frequencies if not properly tuned to motor characteristics....If you need the fan to be operational within these unstable speeds then you can probably go with PWM (pulse width modulation) type control, however either type drive should be tuned to the specific motor....the motor manufacturer should be able to help...

http://www.engdyn.com/images/uploads/96-vfd_torsional_-_turbo_2008.pdf

Dear Mr.Solar Eagle,

THANK YOU FOR YOUR RESPONSE.

Your posting is highly educative.

DHAYANANDHAN.S

What SolarEagle said above.

Check your VFD manual and application notes carefully, if your VFD has a self tune function and your trying to use that rather than entering specific motor parameters then that could be your problem. That our perhaps your carrier frequency setting is too low, it sounds like one or more of your VFD settings is incorrect.

Dear Mr.jack of all trades,

THANK YOU FOR YOUR RESPONSE.

I will try and post the results.

DHAYANANDHAN.S

Are you referring to the vibration levels (as e.g. measured by bearing condition monitoring devices) or simply to the audible noise?

Torque ripple can be an issue but unless using a low-end drive it could likely point to a sub optimal parametrization of the drive.

Dear Mr.Plimos,

THANK YOU FOR YOUR RESPONSE.

It is not the sound based observation.

We have measured the vibration with instrument.

DHAYANANDHAN.S

Dear Mr. Simple Mind,

THANK YOU FOR YOUR RESPONSE.

Perhaps, the resonance may be one issue. I will check up and post the information.

DHAYANANDHAN.S

My experience with both Rockwell Powerflex AC, and ABB ACS800 drives has been I have to uncouple the motor from the load to get decent SVC or DTC control to work as expected with the motor ID Auto tune. Then I connect the load for the speed loop Auto tune.

Perhaps others have had different experiences.

Make sure the VFD drive has no problems, like a blown drive transistor. Check the wave form. It will be obvious if the output is not a reasonable facsimile of a pure sine wave.

Really? For industrial AC drives I have only seen a good sine wave when copious additional filters have been added.

My little Honda generator does have near perfect voltage waveform - but that is not an industrial motor drive.

My experience is the carrier is so dominant that the voltage waveform is "magic".

The AC amps are usually much better in waveform, but there are still large amounts of spikes and noise from capacitive charging.

Good drives monitor their IGBTs. And without sine filter (quite expensive and typically you can only run scalar mode with such filter) you don't get much of a sine wave.

About not using vector mode, once again, you should only use the scalar mode if technical reasons prevent you from using a vector mode (like e.g. using a sine filter, step up transformer, driving multiple motors or so).

Dear Mr. Dhayanandhan, Normal AC supply is pure sinusoidal wave form, however the VFD supply is not so good sinusoidal wave form because it is produced by Pulse Width Modulation technique. The result is non uniform torque pattern, consequently a jerk is produced during the motion & thus vibrations and noise. Hope icould be able to clarify the phenomenon. Regards Murtaza Hussain Kazimi

Thank you Mr.MurtaaHussain Kazimi, for your comments.

The question is when the other identical system is working with out any difficulty, why this particular installation has the problem.

The power supply is more or less same, since identical units are installed, and the VFD supplier still not concluded the issue.

DHAYANANDHAN.S

There may be some valuable info. you can get from the VSD software.Torque, current and voltage graphs, this tool may be able to point you in the right direction.

Also, Is the switching frequency set correctly?

Looking at it from a different POV, does the vibration 'settle' out over time or is it persistent? With 120 HP @ 1000 rpm the fan you are driving must have very large inertia and if the frequency is adjusted lower than full frequency then it may take some time for the 'fly wheel effect' of inertia to sync with the new frequency and during this transition time there may be more than usual vibration.

Have you tried immediately speeding up the fan when you switch to the VFD? Maybe the vibration form would be different than slowing the fan.

Good Luck.

@OP:

OK, thanks for your reply.

Don't know which VFD you use but good ones have some tools including drive-integrated as well as external PC software for data logging, so you should be able to check some oddities. Also try to find out if there are vibration conditions you can reproduce at some specific speeds. If so program the drive in a way that those resonance zones are crossed as quickly as the system allows it (again, in better drives you can tailor the acceleration curve or at least pass critical zones quickly).

Of course commissioning more advanced drives requires some hands-on experience, you won't learn it only by reading the 1000 pages of the manuals. If required you can also modify the regulation algorithms but that depends on the used drive.

And BTW make sure that the motor indentification run (ID run) procedure is well understood, depending on the driven load (where applicable including transmission elements) you may perform a full or only a limited ID run.

Make sure the motor nameplate details are entered correctly into the drive.

Sorry for my stupid typo.

ID Run = Identification Run.

It's a feature used during drive commisioning which allows the drive to auto-tune some parameters (some of those parameters may be editable manually if required details depend on drives).

Typically there are several levels of ID Runs.

Very important is to be extremely careful when performing dynamic ID Runs (i.e. the motor shaft is rotating) as in some cases the load or transmission components could be damaged due to high torque pulses, be also aware of possible rotation direction changes.

If a full ID run with coupled load cannot be performed, at least a reduced ID Run with only the motor (load NOT mechanically connected) should be performed.

For details always carefully check the drive manual corresponding to the exact drive type, size and firmware type (for drives available with different firmware types) and installed firmware version.

Here is a good article discussing induced harmonics when using a VFD:

http://electronicsmaker.com/mitigating-harmonics-caused-by-variable-frequency-drives-vfds

Dear sir,

First of all i thank you sir,I am really happy with your good feedback,

I face problem with vibrofeeder thyristor& firing module,i want to check the problem with thyristor/firing module.

1)system voltage 2 phase

2)operating current 7Amps

3)one phase controlled by single SCR

I check the voltage at input of SCR ---OK,

I fit new SCR---So SCR is OK

suggest me testing procedures

RK