Cure for Harmonic Vibration?

Status
Not open for further replies.
Talked with my Dad (also an electrician) and mentioned this crazy spec. He laughed and said that it sounded like the work of (engineers name withheld).
Oh yea, its the guy he mentioned! He went on to tell me a little bit about the work of this "engineer".

Apparently, this is a guy with a calculator, a code book, and a stamp with his signature on it, that fancies himself as a real engineer. You know, old school, the kind that could think of an idea, draw it up, build it and maintain it. Much like the German's require of their engineers. From what my Dad was telling me, this guy comes up with these bizarre ideas that have no function. Either it makes the guy feel like he's actually designing something or it's a signature thing similar to an architect putting a certain type of window in every building he designs.

I'm going to copy the detail and spec. from the print and save it to my wall of shame. A collection of the electrically insane.

He told me to go ahead and RFI it, just to document the insanity. He also told me not to challenge its validity, as it would upset "His Highness" who would then make it his business to make my job difficult. This guy must be a real piece of work. Sure hope he doesn't visit this forum.:D
 
Transformer vibration

Transformer vibration

Silly as it sounds, transformer vibration can be conducted through solid ground or conduit and if mechanically connected to a room or house that resonates at a low multiple of 120 HZ, it can be a bitch to get rid of and can be very annoying.

As the phase voltage changes, especially between 2 single phase transformers (on different phases) (with just the right (wrong) spacing, the noise can appear to come and go, or move.

Don't discount that engineers experience until you've had to try to get rid of a hum compliant. Likely he has lived that problem.
 
beanland said:
I would ask the engineer if it was an acceptable alternative to place the transformers on vibration isolation pads? A few little pieces of rubber would be cheap and more effective than moving transformers around.

Is there also a spec that says that electrical equipment must be true and level and at right angles? The 5 degree spec will conflict with that spec.

And, 5 degrees off from what? That is an RFI.
Click to expand...

The isolation pads eventually disintegrate and would need to be replaced. (Just like engine isolation pads.) 5 degrees is alomst imperceptible to the eye, but it certainly create an odd feeling to the observer as something isn't right but unable to pinpoint it, unless he is 'blessed' with OCD:smile:.

The 5 degree displacment is meant to be applied in all three axees.
 
Pitch, Yaw & Roll

Pitch, Yaw & Roll

If structure-borne vibration is an issue, spring isolators would be the cure. If air-borne sound where the engineer wants to avoid resonance, it is not an issue. Sound travels at about 1140ft/sec. Normal transformer sound is 120, 240, 360, 480Hz. A 1/2 wavelength at 480Hz is ~14". Any space smaller than 14" is unlikely to resonate. At 240Hz, the transformer needs to be 28" away from the wall to resonate.

I love the visualization of a transformer pitched 5 degrees, yawed 5 degrees and rolled 5 degrees. It would be standing on one corner, looking like it is ready to fall over.
 
We have worked in many high rise buildings which have typical electrical rooms from one floor to the next. Maybe the typical(same manufacturer) transformer might be a 75 kva to feed the low voltage panels. Some of them are just noisy and nothing changes them!! Must be in the core make up ? We have had to change a few out due to noise!!
 
charlietuna said:
We have worked in many high rise buildings which have typical electrical rooms from one floor to the next. Maybe the typical(same manufacturer) transformer might be a 75 kva to feed the low voltage panels. Some of them are just noisy and nothing changes them!! Must be in the core make up ? We have had to change a few out due to noise!!
Click to expand...

Some manufacturers install floating cores in the shell and have shipping screws fastening the core to avoid damage during transit. These need to be removed for optimum 'sound' performance.:smile:

When everything fails; read the manual......:D
 
Documentation please

Documentation please

Barryfish said:
Silly as it sounds, transformer vibration can be conducted through solid ground or conduit and if mechanically connected to a room or house that resonates at a low multiple of 120 HZ, it can be a bitch to get rid of and can be very annoying.

As the phase voltage changes, especially between 2 single phase transformers (on different phases) (with just the right (wrong) spacing, the noise can appear to come and go, or move.

Don't discount that engineers experience until you've had to try to get rid of a hum compliant. Likely he has lived that problem.
Click to expand...
What proof does he have that moving it 5 degrees will not bring it to a resonant orientation? Has he made some kind of resonant frequency measurements? His spec sounds kind of arbitrary to me. It may not be, but it sure sounds fishy. I would like to see some documentation that 5 degrees is going to do anything, and how that specific determination was made.
 
beanland said:
I love the visualization of a transformer pitched 5 degrees, yawed 5 degrees and rolled 5 degrees. It would be standing on one corner, looking like it is ready to fall over.
Click to expand...
Here is a quick and dirty visualization:
5degreetransformer.jpg
 
weressl said:
When everything fails; read the manual......:D
Click to expand...

Nonsense! Men never read the manual, and engineers never read the manual. Therefore, you have absolutely no hope with a male engineer. :D

mivey said:
What proof does he have that moving it 5 degrees will not bring it to a resonant orientation? Has he made some kind of resonant frequency measurements? His spec sounds kind of arbitrary to me. It may not be, but it sure sounds fishy. I would like to see some documentation that 5 degrees is going to do anything, and how that specific determination was made.
Click to expand...

Haha good point. That 5 degrees could actually cause a problem if there wasn't one to begin with.

I would imagine that a request for documentation would get you nothing at best, and a "just do what I say because I'm an engineer and you're not" at worst. :grin::roll:
 
mivey said:
What proof does he have that moving it 5 degrees will not bring it to a resonant orientation? Has he made some kind of resonant frequency measurements? His spec sounds kind of arbitrary to me. It may not be, but it sure sounds fishy. I would like to see some documentation that 5 degrees is going to do anything, and how that specific determination was made.
Click to expand...

That is a standard way of getting rid of resonant frequencies, not need to 'study it'.:rolleyes:

Although I am sure we can make it a Guvernment study via OSHA and blow couple of $M or more. Better use though than the blowfish' mating rituals.....
 
weressl said:
...5 degrees is alomst imperceptible to the eye...
Click to expand...
The rendering in my post #28 is a 5 degree rotation on each axis...looks pretty "perceptible" to me.
weressl said:
That is a standard way of getting rid of resonant frequencies
Click to expand...
Seez who? I would be interested in more info that shows rotating a transformer 5 degrees to a building will reduce resonance. Thanks.
 
mivey said:
The rendering in my post #28 is a 5 degree rotation on each axis...looks pretty "perceptible" to me.Seez who? I would be interested in more info that shows rotating a transformer 5 degrees to a building will reduce resonance. Thanks.
Click to expand...
I said 'almost'.

Seez I, as far as I can tell.

It's basic physics. That is how things work, in other words. If you interested, take a physics course. Talk to structural and mechancial engineers. Search for any literature on resonant frequency mitigation. There is a ton of them out there.
 
weressl said:
It's basic physics. That is how things work, in other words. If you interested, take a physics course. Talk to structural and mechancial engineers. Search for any literature on resonant frequency mitigation. There is a ton of them out there.
Click to expand...

So rotating anything 5 degrees in relation to something else will make it impossible for harmonic vibration to occur, period? I don't remember that in Physics, and I had several courses. :cool:

Sorry, but sez you ain't good enough for me. ;)

Either post a source, or admit you're making this stuff up cuz its funny. :D:D
 
not quite a ton

not quite a ton

weressl said:
It's basic physics. That is how things work, in other words.
Click to expand...
I don't think so, Tim. Sounds to me like you are mis-applying some generalizations you may have remembered from somewhere.

The world rarely works that simple (Murphy's Laws excluded, of course). If we think back to our college days, we must remember a lot of those labs were "rigged" to produce a specific result, so we could learn a little something. Wouldn't it be nice if the world was as simple as our college labs?
weressl said:
Search for any literature on resonant frequency mitigation. There is a ton of them out there.
Click to expand...
resonantfrequencymitigation.jpg


In all fairness, I will try to find some real resources to validate what you are claiming. If you would care to stop winging it and actually assist in finding some of those tons of resources, it would help.
 
mivey said:
I don't think so, Tim. Sounds to me like you are mis-applying some generalizations you may have remembered from somewhere.

The world rarely works that simple (Murphy's Laws excluded, of course). If we think back to our college days, we must remember a lot of those labs were "rigged" to produce a specific result, so we could learn a little something. Wouldn't it be nice if the world was as simple as our college labs?
resonantfrequencymitigation.jpg


In all fairness, I will try to find some real resources to validate what you are claiming. If you would care to stop winging it and actually assist in finding some of those tons of resources, it would help.
Click to expand...

Forces in the same axees are additive. Does that help for starters?

Google returns to me Results 1 - 10 of about 43,300 for resonant frequency mitigation. (0.12 seconds)
 
weressl said:
Forces in the same axees are additive. Does that help for starters?
Click to expand...
But there's the rub. Why would you assume that the axis of a building and the axis of a transformer cabinet are additive? What forces are they talking about?

I can see that it might dampen some reflective noise/radar/whatever to have varying surface angles (the stealth fighter is a good example) but I'm not sure that would help with any ground vibrations. I would think that would be more of a function of the internal structure of the transformer. Perhaps a 90 degree angle is the perfect angle to dampen some of these ground vibrations.

weressl said:
Google returns to me Results 1 - 10 of about 43,300 for resonant frequency mitigation. (0.12 seconds)
Click to expand...
I found about 497,000 Google hits in 0.18 seconds on:
chicken little fell from the sky while eating dog food
but I don't think they all deal with chicken little falling from the sky while eating dog food. Take some night classes and learn how a search engine works.
 
mivey said:
But there's the rub. Why would you assume that the axis of a building and the axis of a transformer cabinet are additive? What forces are they talking about?

I can see that it might dampen some reflective noise/radar/whatever to have varying surface angles (the stealth fighter is a good example) but I'm not sure that would help with any ground vibrations. I would think that would be more of a function of the internal structure of the transformer. Perhaps a 90 degree angle is the perfect angle to dampen some of these ground vibrations.

I found about 497,000 Google hits in 0.18 seconds on:
chicken little fell from the sky while eating dog food
but I don't think they all deal with chicken little falling from the sky while eating dog food. Take some night classes and learn how a search engine works.
Click to expand...

You were the one who said you can't find any?

Ahhh, so you sent away to the Video Professors CD?! Good for ya....Attaboy, be proud of yourself.:D

I suggest you search how the Japanese deal with earthquakes besides active dampening systems. The issue is MITIGATING the potential to transmit noise. The main members of the building run at right angles in three different axees. The more rigid the memebr is the better conductor that is. The mechanical connection is the route how the vibration is transmitted, if there are dampeners, such as springs or rubber insterst are used, the force is absorbed and the transmitted force is lessened. Along long straight paths of force conductive media - main structural mebers of buildings - sympathetic frequencies are found and as being additive they amplify each other. When the force is transmitted in axis to the conductive media the maximum transmission occurs and dependent on the length different resonant frequencies may be found where the natural frequency of the member get 'excited' by the transmitted force and could result in actual structural failure. Dampening, angular displacement, varying mass, force absorption and disruption of natural frequencies are just a few of the methods how frequency sources are neutralized or mitigated.
 
Status
Not open for further replies.
Top