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Tagged With "VFD"

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VFD Security Risk

Reliability ·
Vendors include this setting intentionally in the device’s registry so operators will always know the top speed-limit for motors. But the devices reveal this critical speed to anyone who queries them. They use the Modbus protocol to communicate, and a hacker can send a simple query to the drive’s control board to obtain this critical information then use it against the device.
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3X dominant vibration in Overhung belt drive VFD fans.

fraaanklinn ·
Does less internal bearing radial clearance plays in 3X vibration?
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Chain Lift Motor/Gearbox 1/2X

Mike Gawlik ·
I am hoping someone can help me out a little. I am fairly new to the PdM game and since we started to perform vibration on our VFD driven motor/gearboxes that run a chain lift for ride vehicles. (Think rollercoasters). Anyway, the issue we see on all of the motors and gearboxes that run these lifts is a high peak around 1/2x (it varies slightly per ride/lift) In the attached file, you can see that we have a 0.533 order peak on all measurement points for the motor and gearbox. This value will...
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Re: High 2660 CPM vibration at variable speed 4 pole electric motor

Bill Keeter ·
Does this occur in one motor only, or in all six?
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Re: High 2660 CPM vibration at variable speed 4 pole electric motor

Ander ·
Proceed a shutdown test, you will know if the vibration comes from eletric problem.
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Re: High 2660 CPM vibration at variable speed 4 pole electric motor

Rotate ·
I have seen and corrected vibration problems coming from the VFD controls. Change the VFD control speed and see if it goes away. If it goes away, look into the controller.
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Re: High 2660 CPM vibration at variable speed 4 pole electric motor

Callum S ·
if the vibration frequency of interest is present on all 6 machines it may be from another source completely. 2660 / 3 = 886 rpm . Possible vane pass from a nearby pump or mixer etc rotating at 886 rpm?
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Re: High 2660 CPM vibration at variable speed 4 pole electric motor

Dave Reynolds ·
What does the vibration do when you run the motor slower or faster than 87-97%? What type of bearings are in the motor? 1) Data you posted shows a high 2x TS peak, the ratio of vibration from 1x to 2x is over 4:1, this is not normal, can indicate a resonance issue. 2) At the base of the 2x TX peak, notice how it has a small "haystack" of energy, this is can be an indication of a natural frequency, done any bump tests, startup/coastdown tests? 3) With the motor running at trouble some speeds,...
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Re: VFD Control For Positive Displacement Blower

Dave Reynolds ·
http://www.efc.sog.unc.edu/sit...r%20Optimization.pdf http://www.eng-tips.com/viewthread.cfm?qid=256028 Here are a couple of resources that may help you understand the complexity of VFD control on PD blower. Also keep in mind machinery critical speeds.....most machinery is designed to operate within a speed range, you put the machinery on a poor base/structure and you will have natural frequency issues. To compound the problem is the pulsation frequency of the blower and gear mesh which will...
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Re: VFD Control For Positive Displacement Blower

David Hawkes ·
Thanks for your insight!
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Re: VFD problem?

Panta ·
Cando, Which is type and power of your regulator .Theoretically in large High Voltage regulators has several transformers at each stage working together and made output sinusoidal voltage which at one phase obviously lacks. Good luck !
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Re: 3X dominant vibration in Overhung belt drive VFD fans.

Dan Timberlake ·
What are the BPFrequencies of the fan bearings? Some are remarkably close to 3X. Like in the range of 3.06 X rotation.
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Re: 3X dominant vibration in Overhung belt drive VFD fans.

John from PA ·
Probably not...adage taught in medical school, "if you hear hoof beats think horses, not zebras." Look elsewhere, maybe review content at http://www.vibrationschool.com...ter/SpecInter15c.htm . VFD could be suspect. Provide more details here, photograph, pulley ratios, bearing numbers, data, etc. Does the 3X drop immediately when you cut the power, thus supporting an electrical issue or does it remain, supporting a mechanical issue?
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Re: 3X dominant vibration in Overhung belt drive VFD fans.

Hossam 2 ·
first of all you please post more details about the machine and i prefer to perform the some mechanical checks before suspecting anything. 1) Sheaves run out Not more than 0.1 mm. 2) the shaft run out near bearing ends and at shaft centerline also (not more than 0.05 mm or sometimes not more than 0.07 mm.) 3) Belts condition and misalignment and also check the sheaves width to be the same i saw a fault from the preparation department they brought two sheaves with different width. regards'
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Helical Gearbox failure and sub-synchronous axial vibrations

msmemon ·
Hi , I have seen a number of very useful posts on this forum specially on the gearboxes and would like opinion of members on failure of double helical gearbox with three teeth of compressor side helix found broken during a preventive maintenance inspection. The unit consist of a VFD driven 7 MW motor (1800 RPM), a speed increasing double helical gear and a compressor. The failed Gearbox had operated about 25000 hours since installation. The history of this unit is that it was commissioned in...
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High 2660 CPM vibration at variable speed 4 pole electric motor

Alvaro Loayza ·
Hello, We have 6 sulzer centrifugal pumps that are driven by a 3250 HP, 1785 RPM nidec electric motor each one. The electric motor has a VFD and it operates only between 87% and 97%. The strange situation is that the motor has high level of vibration coupled and uncoupled at a 2660-2670 CPM frequency. I suspect that the problem comes from the electric motor and not from the pump because of the uncoupled test that was made. Attached you can see the spectra that was taken. If you have an idea...
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Re: Motors Hunting Mag Center

edisonindia ·
Motor mag center hunting is common in sleeve bearing machines. As long as the rotor shaft labyrinth edges do not touch the bearings sides and there are no vibration or temperature issues, they are not a problem.
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Re: Motors Hunting Mag Center

Mile High_PumpFE ·
EdisonIndia Thank you for the reply - the problem is the coupling....the motor vibes are acceptable however.... this axial motion is killing the shim packs in the Thomas series coupling and creating a significant safety concern.
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Re: Motors Hunting Mag Center

Shurafa ·
3 identical pumps run in parallel. 2 pumps run at 3570 rpm while the VFD can run at 1800-3535 rpm. If this is a successful setup, there must be additional parts of the system to avoid hydraulic problems. As you know, pump discharge pressure and flow are dependent on the speed. If the 3 pumps deliver to the same header, the pump(s) with high speed will boost the header pressure and the VFD pump (if running at a lower speed) will not deliver. If there is a hydraulic problem, will that cause an...
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Re: Helical Gearbox failure and sub-synchronous axial vibrations

Bill Kilbey ·
John in PA would be your best resource on this board in this matter.
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Re: Motors Hunting Mag Center

Walt Strong ·
Bronco Fan, Have you measured the frequency of the axial shaft motion? If yes, does it match anything of electrical or mechanical origin? You can test the motor to verify/eliminate it as a source, but I would look at the shaft coupling and pump for the root cause. The disk pack coupling is a spring with motor rotor mass on one side and the pump rotor on the other. The pump would be the source of the force that drives the motion. I have seen this on boiler feed pumps. Walt Patriot Fan
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Re: Motors Hunting Mag Center

Mile High_PumpFE ·
Shurafa - These pumps run in series.... not parallel. They are using the VFD to throttle the performance of the pumps as opposed to controlling them using a motor operating valve. Hi Walt - Yes... I have collected axial vibe data on both the pump and motor.... there is a dominant 2x at approximately .1 ips (well within acceptable limits) on the MIA and POA positions..... there are some electrical signatures present out around 50x TS on the motor however the amplitudes are extremely low. My...
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Re: Motors Hunting Mag Center

Walt Strong ·
"Just a note - vane pass is the real reason this customer brought me to site." What was the resolution to this issue? Is the pump operating close to BEP on the variable speed curve? The pump rotor may be limited to 0.008" axially as limited by the thrust bearing, but the pump can still provide the excitation force. The coupling is an axially soft spring, so higher motor rotor motion is not surprising. I would measure the frequency of the axial motor shaft motion. You can always use a stop...
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Re: Motors Hunting Mag Center

Mile High_PumpFE ·
Hi Walt, We are looking at re-rating these pumps to change the vane combo..... the current arrangement is exciting NF's both on the valves and piping. I was unable to get accurate flow data at this site due to a lack of available straight piping (need 5x dia of straight run - minimum of 3x dia to get a good flow reading). The customer was able to give us a thumb in the air rate they were pumping, I am working to plot that data now. With your comments in mind, please see the attached...
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Re: Motors Hunting Mag Center

Walt Strong ·
Unfortunately, not very useful data for motor shaft axial motion. The housing resonance frequency may or may not match the shaft motion frequency. Walt
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Re: Helical Gearbox failure and sub-synchronous axial vibrations

Dave Reynolds ·
NOT the expert on this subject, what I see in data provided is axial thrusting on the double helical gear teeth. This can be caused by unlevel gearbox and worn gear tooth profile to name a couple. The gear tooth broke toward the outer edge of the gear which too can indicate axial thrusting. Sub synchronous, do you mean vibration is below motor or compressor shaft speeds? Are the failed gear teeth next to each other or just a couple of teeth apart? Can you share more data, gearbox...
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Re: Motors Hunting Mag Center

jvoitl ·
To get back to basics, was the magnetic center of the motor taken into account when the pump and motor were connected?
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Re: Motors Hunting Mag Center

Ron Brook ·
First of all, you can't possibly have 1/8 inch of axial hunt if the coupling was doing it's job in the first place. These couplings should be changed to a falk style with limited end float. And, please!!! Don't get me started on mag center!!!!! It doesn't matter!!!!
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Re: VFD Motor solo run

Balbi ·
I do and suggest taking at max speed, most common operating running speed and a Coast down data.
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Insulated Motor couplings

Jack1954 ·
I was talking to someone about a customer he had. They have VFD's on their machine and fluted the gearbox input bearing. There going to install a grounding brush on the motor shaft. I don't see how there going to keep it clean. I was thinking about insulated coupling to isolate the gearbox from the motor. That should at least keep the gearbox from fluting. Has anyone had any experience with these couplings. Not sure the horsepower It's a forming roll so probably 1000 or so.
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Motor/Pump issues

ChemEric ·
Hi all, I have a centrifugal pump/motor driven by a VFD that makes a very disconcerting sounds as it speeds up (hear attached video) The motor had alleged never been regreased (note Zerk fittings) and sits in a location where it is is often exposed to steam. Given this context, I think that it's not unlikely that the sound is coming from the motor bearings. However, removing and sending the motor off to be fixed is quite a hassle and expensive here in Spain and I'd feel a lot better the more...
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Motors Hunting Mag Center

Mile High_PumpFE ·
Have a pipeline customer that has three 3000 HP motors driving main line pipeline pumps that are hunting mag center. These are Mitsubishi AC induction motors, 4160V, 60 HZ, 360 FLA, rated for 3570 rpms..... these motors are set up so that any given motor/pump combination can be run through the one VFD on site, and the other pump/motor combo can be run across the line at full speed (always running two units at these stations..... one in VFD to throttle flow, one across the line at full...
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Re: Insulated Motor couplings

Jack1954 ·
You have to put the brush outside this motor. They get dirty and water and pulp on them and may or may not work all the time. I want to use an insulated coupling so the voltage does not reach the gearbox.If the grounding brush gets to dirty i want the motor to flute not the gearbox.
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Re: Insulated Motor couplings

John from PA ·
Check the Aegis system at https://www.est-aegis.com/index.php . I really doubt you will find a insulated coupling rated for 1000 HP, but then we don’t know your RPM so don’t know the torque which is the key factor in sizing a coupling.
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Re: Insulated Motor couplings

Dave Reynolds ·
http://www.coolblue-mhw.com/ I have personally used this product on 200HP 1800RPM 480V motor, changed motor bearings, added this product, been running for six months with no problems. How much are you willing to dive into the problem to find the root of it? Doing the proper testing will identify bad grounding, voltage spikes, volts to ground from shaft, current going through the motor shaft end to end......If you stop the source the other problems may disappear...
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Re: Insulated Motor couplings

John from PA ·
I’m an ME and in spite of a year of EE, I stay away from motor electrical stuff. But it would seem to me that if I isolate the gearbox from the motor, that might take care of the gearbox issue, but the stray voltage might still be present, and now has to take a path through the motor bearing to ground. So why wouldn’t a grounding mechanism from shaft to ground, like the Aegis system, still be necessary?
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Re: Motor/Pump issues

ivibr8 ·
Chemeric Do you have vibration data to go with the video? Also, you state that its "doubtful" it has never been greased. Is the video/sound taken in that state? If not, have you tried to regrease and see if it still sounds the same? You probably realize this now but this machine and any other machines should be on a documented lubrication program. Jim P
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Re: Motor/Pump issues

Walt Strong ·
I had no luck running video. Jim, did you play it? Walt
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Re: Motor/Pump issues

ivibr8 ·
Yes....the video and sound played fine. You're not running Windows Vista are you? See link below The motor/pump was running at some speed and ramped up to a higher speed. You could hear a somewhat high pitch sound which got louder and with a higher pitch as you might expect. It was hard to figure out (at least for me) whether it truly was from the bearings or perhaps some electrical noise. JIm P https://www.youtube.com/watch?v=-IfnjBHtjHc
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Re: Motor/Pump issues

Walt Strong ·
Jim, What was that garbage in the U-tube link for? Walt
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Re: Motor/Pump issues

ivibr8 ·
Oh...just a joke (poke?) about Vista OS..... and whether you couldn't view the video because you might be using it.
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Re: Motor/Pump issues

ChemEric ·
Hi Jim and Walt, Thanks for trying and watching the video. Since then, I have done some things. First of all, taking off the pump head (but not adapter and coupling) = sounds worse. Then, I spoke with the operator who had said he had regreased the motor for the first time in so many years last month. Turns out he used the food grade aluminum soap grease we use elsewhere in our process... So I went and purchased some NLGI 2 lithium grease (manual recommends 3 but that's too hard to find here)...
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Re: Motor/Pump issues

ivibr8 ·
Ok....most likely you have a bearing fault problem but this type of diagnosis is VERY hard to confirm without quantitative vibration data. Based on your response, sounds like you have no vibration monitoring program at all....or, you do but this machine not monitored because it is less than 10kW ? In any case, the decision to monitor a particular machine should be based on more than its size; the fact you posted this issue on this forum indicates this machine probably needs to be part of...
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Re: Motor/Pump issues

Walt Strong ·
I am surprised that you are trying to run a centrifugal pump at 20% speed and get any flow out of it. If the motor nominal speed rating is 1800 RPM, then 20% speed is only 360 rpm. It would be a little difficult to listen for bearing noise at such a low speed; especially with the electrical noise from the VFD. I'm also not sure what you mean by taking the head off the pump running it. If the motor bearings have not been lubricated in years, and with the wrong grease, then how can one assume...
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Re: Motor/Pump issues

ChemEric ·
Hi y'all, You're right at 20% there is no flow and in fact here in Europe with 50 Hz it's only 1500 rpm (1455 on the plate). I was only running it this slow (essentially just the motor - removed pump casing, impeller, and m/seal but there is what Alfa Laval calls an adapter instead of a coupling that I left on) because the noise is quite evident even at this speed. When you say noise from the VFD, I'm a little unaware of what you mean... I'm definitely still learning the practicalities of...
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Re: Resonance Response - Pipeline pump

OLI ·
Remember the impact test is made when machine is not rotating so compared to running it may differ like 10% or so depending on influence from disc, bearing stiffness etc. due to influence from rotation so your machines behaviour may only follow normal Murphy law implication. It may also be a combination of resonance width and the amplitude of the impulse/excitation vibration that is working against logic. So there may be some work to do. Have fun.
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Re: Resonance Response - Pipeline pump

Dave Reynolds ·
Questions, did you also impact the pump or impeller? or is the first page of your post actually taken on the motor? Can you provide data from all measurement points or is the vibration on the pump only? Are both pumps showing the same problem or just one? Do you have any process data to go with the measurements to see if the flow is the exciter? Do both pumps draw off the same tank, discharge into a common header, have the same size impellers? Was the inlet conditions changing during data...
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Re: Motor/Pump issues

JRaef ·
It's difficult to tell if the sound is abnormal, because we don't know what it sounded like before. I hear the tell-tale whine of a VFD carrier frequency (the rate at which the tiny little DC pulses fire), but if this is above and beyond that, you may have EDM damage to your bearings because of the VFD output and poor grounding. EDM damage is the result of a voltage build-up between the stator and rotor as a result of the high frequency pulses from the VFD causing what's called "common mode"...
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Re: Chain Lift Motor/Gearbox 1/2X

Beatnik ·
Are you sure your speeds are exact and that it's not always exactly 0.5x or another number?
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Re: Chain Lift Motor/Gearbox 1/2X

Beatnik ·
Also please take a Spectrum with better definition. More lines and a lower Fmax.
 
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