Cause of RFI during chiller compressor operation
Cause of RFI during chiller compressor operation
(OP)
As soon as the newly installed chiller starts-up the reception on AM radio signal disppears for appx. 5-6 blocks. The 200Ton chiller is equipped with harmonic filter. Equipment manufac. has replaced all circuit boards, the SCR panel, installed isolation transformer, chokes around the cables, installed PVC on incoming power conduit, etc. but made no change.
You can basically hear compressor motor whining-distortion on AM radio anywhere from AM500 thru AM1500.
To start with grounding from 480V Main panel to isolation transformer to chiller starter enclosure to compressor motor was checked for proper installation as per NEC and verified OK. Plan was to set power analyzer to check for waveform distortion including the equipment ground.
As soon as chiller is shutoff the AM radio signal comes back to normal. Appreciate any help to narrow down the cause.
You can basically hear compressor motor whining-distortion on AM radio anywhere from AM500 thru AM1500.
To start with grounding from 480V Main panel to isolation transformer to chiller starter enclosure to compressor motor was checked for proper installation as per NEC and verified OK. Plan was to set power analyzer to check for waveform distortion including the equipment ground.
As soon as chiller is shutoff the AM radio signal comes back to normal. Appreciate any help to narrow down the cause.





RE: Cause of RFI during chiller compressor operation
PWM inverters emit powerful HF noise and that is what your AM radios are picking up. NEC doesn't have anything with HF pollution to do, FCC has. So, you have to apply other knowledge than power electrical to this.
A power analyzer will not show what is going on simply because it doesn't have the necessary frequency range. Use an HF high-pass filter plus an oscilloscope to see what is going on.
The simplest and usually quite efficient remedy is to use common mode filters (HF ferrites of the correct quality) on the mains and motor cables. You need a specialist to deal with this. I would talk to the supplier of the compressor first. If that doesn't help, I would talk to the VFD manufacturer.
Where in the world are you?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
The question is that this is a brand new unit, and apparently something is wrong. I just started on this case, and plan to check for cable/wiring seperation at inside chiller enclosure all the way to sensors, etc.
Has anyone experienced this same situation? we are talking professionaly so "please do not respond if did not experience this same issue before". Thanks a lot.
RE: Cause of RFI during chiller compressor operation
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
The 480V incoming cable enters the enclosure from the top (conduit piping shown), 3-phase lands on chiller disconnect switch (ground conductor on GRD lug, power feed goes thru VFD/SCR, departs to compressor disconnect (with ground), and then to compressor peckerhead.
Plan was to start investigation and check for electrical/control wiring seperation, collect data and determine why only this unit is causing RFI and no other York unit according to factory floor, crack the case and share the information to help others.
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
The reason I said you probably have a VFD was that you mentioned an SCR panel, which implies a DC motor. And those do not emit nearly as much EMI as VFDs with IGBTs do.
I do not think that anything is broke or defect in your compressor. IGBTs just output lots of radiated EMI and the fact that the unit is brand new does not change that.
There are two basic methods to keep the inevitable EMI from getting out of the enclosure. One is to block HF. That is done using correct quality (with f0 well abobe 1 MHz) ferrite or nanocrystalline toroids. The other is to short the HF energy to ground. And using short braids to do that. The latter metod means that your ground (and usually same as PE) gets polluted with HF current. So it isn't a good method.
Blocking as close to the inverter as possible and doing it with enough HF ferrite cores is usually what works best. Use ferrite cores both on grid side and motor side, but be sure that you only put the three phase cables through the cores. The toroids will saturate if you do that wrong. They will usually also overheat.
In severe cases, you may need quite a few of those ferrites. See attached picture. I was not allowed to remove the protective grid to take the picture. So you have to 'see through' it. You may also need to make the cabinet HF tight. Removing paint and using metal mesh or beryllium bronze fingers between frame and covers and doors may help.
If you are in Europe, there are limits for permissible emission and you can tell the manufaturer to deliver another unit if it cannot be 'silenced' to levels below these limits. In the US or other places, I don't think that you have that possibility.
Most manufacturers do not understand this very well. Sad but true. I will visit a York compressor for a slaughterhouse on Monday. They have have fitted toroids but now, there is a bearing problem also. What make is your VFD?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
You might want to consider adding fine-mesh stainless steel or brass screening to the inside of the louvered panel doors, spot-welded in. In principle it is acting like a radio transmitter. This seems to be the practice on radio transmitter cabinets. Also the doors have to be bonded to the cabinet by braids as said before.
Worth a try.
regards, rasevskii
RE: Cause of RFI during chiller compressor operation
FYI-It's a packaged York unit. I will be in Burrie, Ontario on Monday but the chiller facility is located south of Champaign, Illinois. Plan to head there the week after next when the folks come back from Thanksgiving holidays.
One thing I noticed: looking at the pictures received it shows a few ferrite cores installed on cables going to harmonic filter/coil to SCR block. Regarding the ground conductors going to each compressor (from enclosure), I'm not sure if they are solid conductors all the way to the compressoror motor (or is it OK to rely on frame-enclosure ground to provide the path). Reading your comment I gather that RFI is IGBT-related and more ferrite cores are needed to fix the situation to say the least. Wonder why RFI is affecting this unit and not 100 others previously installed.
RE: Cause of RFI during chiller compressor operation
Louver panels are not equipped with SS or brass screens, but the front doors have braided ground bonded to panel enclosure (side panel).
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
With all cases of EMI, it is not just the aspect of emission that needs limiting but the immunity of other components.
If you are in an industrial environment based on industrial emission levels, then all your products around should be based on "industrial" immunity levels. However, if you have a product in an industrial environment that has "domestic" levels of immunity then you will not achieve parity when looking at compatibility.
Whilst the EU EMC standards are much derided by various circles in North America, they do actually make sense when you have problems.
RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
1) Removed snubbers on drive
2) Grounded chiller with dedicated ground rod
3) Replaced logic and trigger boards
4) Replaced entire drive assembly
5) Replaced inductor
6) Added ferrite beads on incoming and both sides of inductor
7) Added reactor and capacitors on incoming lines
8) Removed line side at chiller and ran unit off generator, this seemed to work
9) Removed reactor and capacitors and added isolation transformer- Problem remain.
Seems like when the chiller was running on generator set the RFI was eliminated completely, indicating suspect cause may be voltage related perhaps.
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RE: Cause of RFI during chiller compressor operation
What is the configuration of the isolation transformer?
Bill
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"Why not the best?"
Jimmy Carter
RE: Cause of RFI during chiller compressor operation
The 480V 3-phase from main switchgear lands on islation xfmr primary (left hand side shown on attached picture), incoming ground lands on xfmr chasis & bonded to xfmr neutral, and departs to chiller enclosure (lands on GRD lug). The 3-phase secondary (on right side) departs to chiller and lands on drive 480V disconnect.
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RE: Cause of RFI during chiller compressor operation
RE: Cause of RFI during chiller compressor operation
Could it be that other units do not work close to where AM radios are used? Or that AM signal strength is much better in other places so that interference from compressors are not noticed?
Again, I do not think that the 'hundreds of other units' are any better than the unit causing problems.
The test with a diesel was probably run with short cables from generator to compressor. That illustrates the importance of cable length. As you know, a conductor starts acting like an antenna when it gets close to 1/4 of the emitted wavelength. At AM 1000, the wavelength is around 1000 feet. So, cables less than around 250 feet will not emit much, while grid cables are much longer and emit much more. So, the test with the generator means that emission is not radiated from the unit, but from the cables.
That makes use of ferrite cores on the incoming (to compressor unit) cables easy and effective.
Why doesn't an isolation transformer work? The reason is that interwinding capacitance is high and lets HF through. If you add a static screen between windings - and connect that screen to a good, low impedance ground and with a short cable - you may also get rid of the interference. But, ferrite cores are much easier to apply.
I think that York should help you with this. They have put the equipment on the market and it is their responsibility to make it clean. FCC 15 is what applies in the US.
I am afraid that Champaign, Illinois is too distant for 'popping in'. I will go directly from Sweden and stay in Buffalo for three days. Going to Illinois and doing some meaningful work will take a couple of days and that would mean money. I think that the York people shall pop in instead.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
The elaboration I would make is quite simply that you can spend many thousands of $$'s improving the emission levels of the said equipment but a few $'s improving the immunity might do the trick. You will not eliminate RFI completely, just getting it sitting within the compatibility levels.
I recall a few years ago in the UK we had an installation with 7 x 560kW VFD's on a water pump station in a quite remote location. All VFD's had the (legally) required EMI filters fitted, the installation was top notch and all was running well until some old dear down the road complained that since the new installation her old TV started getting fuzzy lines. Water authority came to us and asked what we could do. In the end it was either make about $100k worth of investment (I've lost my GBP sign now on my keyboard..) to hopefully keep her happy but in the end we bought her a new TV, top of the range for about $1500. She was as happy as larry, the water authority saved themselves a fortune and our reputation remained intact.
However, if you want an expert on EMI, Gunnar is your man. But don't expect a new TV from him.
RE: Cause of RFI during chiller compressor operation
More importantly, I am concerned with the voltage waveforms posted at 21 Nov 09 20:02.
These wave forms are showing an almost textbook case of a neutral shift. A voltage drop due to load usually shows up on two phases. Here we have a voltage drop on only one phase, but with an accompanying phase shift.
Remember the story of the man who lost his keys in a dark alley but looked for then 50 yards away under the light "Because the light was better."
Given the history of trouble-shooting here and the assertion that this is only one out of hundreds with a serious EMI it may be prudent to investigate other possible sources of interference. I am thinking possibly a poor connection on a transformer neutral that tests good with no load but goes open under heavy loading and possibly arcs under normal loading. I would also rigorously check the motor for possible faults.
I submit this suggestion nervously as I feel that I am in the presence of greatness when Skogsgurra and ozmosis are collaborating on a drive problem.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Cause of RFI during chiller compressor operation
For clarity- York engineer had disconnected equipment ground at both ends (480V Mains & at the isolation XFMR) inserted a new ground rod at foot base of the chiller, connecting ground rod to chiller frame, and bonding via dribbly wire too XFMR ground (thinking this solves the RFI). Grounding system is back to original as per code. The thin copper wire is no longer there as of last Week.
Equipment ground connection between isolation XFMR and chiller- There are 2 pairs of conduit piping departing from isolation xfmr to chiller enclosure carry 3-phase delta and ground (#6AWG) in each pipe. Both ground conductors land on chiller enclosure (GRND lug). I will make sure all connections are tight, but not sure if increasing the size of ground conductor will help the situation. (Attached is as-found with the orginal incoming grounds disconneced-right side is the secondary departing with 3-phase and ground to chiller disconnect).
With respect to voltage sag-drop events during the inrush, it's concern that I need to fix (starting point). Typically the voltage should not decrease but 1-5volts in a good solid system. With load current incresing to 99Amps, voltage delivery decreasing to 250volts, means there is weakness somewhere.
As for the compressor motor, there is no indication of a fault but I plan on running a check to verify OK. Thanks
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RE: Cause of RFI during chiller compressor operation
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
What about the 480V 3 phase incoming supply-how is that grounded-is there a neutral (like a 277/440 system), where is that grounded? Is there a dedicated padmount transformer just for this or a pole mounted cluster of 3 units? What else is connected onto the 480 volt system you have? Maybe you have in effect a broadcast antenna there...
Are there any overhead connections to a pole or is it all in grounded conduits...where are the conduits grounded..Is anything connected to a water pipe ground...Are there any non-metallic water pipes in the system, giving an apparent ground but not actually...
Try removing and reconnecting different grounds as the system is running to see what makes a difference.
What about the schoolyard fence? Is that grounded or not, how far away is that...connect and disconnect that...
I was once dealing with a traction substation where we had a 60 to 25hz static converter in operation. Using a clamp-on meter, hundreds of amps were found flowing in fences, railings, pipes and metalwork all over the site..
Just some thoughts..
regards, rasevskii
RE: Cause of RFI during chiller compressor operation
The conduit piping has PVS added to it right before the isolation transformer and as metallic conduit top entry land on the enclosure, (York thinking that would solve the RFI). So, the answer is yes, there are PVCs in the system piping. Plan was to install jumper across all PVC connections, and place back to original.
At the isolation transformer, 3-phase comes in with the ground conductor bonded to xfmr neutral, and departs from secondary to the chiller. There are no additional ground rods in the system-all removed. There are no over-head cluster-mount 3 pot transformers anywhere nearby, and the school fence is about 500 yards away.
Thanks for your input raseskii. I appreciate that.
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RE: Cause of RFI during chiller compressor operation
Thanks the photo. This may sound ridiculous, but if the building has a metal roof, that may be the antenna... If so, it is probably bonded somewhere to the electrical panels or conduits. If so try breaking that. The roof, if so, has to have grounding at some points legally, I believe. But that can be elsewhere in the building complex.
regards, rasevskii
RE: Cause of RFI during chiller compressor operation
But now that it has been repaired, enough said.
Gunnar, will you take a second look at the voltage waveforms and comment please? It looks to me as if a dirty connection on a transformer primary wye point may be going open under load. I don't see that waveform as causing the EMI, but whatever is causing that waveform may also be causing EMI.
The changes in voltage are too abrupt and too regular to be a reflection of starting current, and it is always only one phase.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Cause of RFI during chiller compressor operation
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RE: Cause of RFI during chiller compressor operation
Also, the influence on AM radios is not something you get from loose connections. But you do get it from a PWM inverter. It outputs a continuous carrier frequency that is more intense than the AM broadcast stations and that is what kills the radio stations. Intermittents do not do that.
I need to repeat that recordings made with a milliseconds timebase never can show details that interfere in the MHz band. To see those, you need a microsecond timebase and corresponding BW. None of the Dranetz boxes have that.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
Yours
Bill
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Cause of RFI during chiller compressor operation
As you can see the line voltage on VFD disconnect decreased to 250volts (when load increased to 99Amps) indicating the existing 500KVA padmount xfmr is unable to support the voltage during the inrush. Padmount (attached picture) may need to be upsized to support the load during inrush as well as under continueous load. I was wondering if undersize xfmr could be a suspect cause-in any shape.
As for arcing, I believe all connections are verified-tight (I will recheck again though). Comments are very helpful.
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RE: Cause of RFI during chiller compressor operation
Data shows minimum load, and yet there is voltage diturbabce (taking chiller out of picture for a moment). Seems like I have to fix this situation first- making sure supply voltage-voltage delovery is good to start with.
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RE: Cause of RFI during chiller compressor operation
Even if it was already 100% loaded, it should sustain an additional 99 amps.
Assume the regulation at 5% (conservative) and full load will be expected to drop the voltage 24 Volts. The addition of a 99 Amp load may be expected to drop the voltage by about 4 volts. A rigorous solution will take power factors and phase angles into consideration, but transformer voltage drop can only explain a voltage drop of around 4 Volts, not a drop of over 200 Volts.
Is it possible that there is a bad connection somewhere on the supply side that is emitting EMI, but notenough to overcome local radio stations? The addition of the chiller load may be increasing the amplitude of such interference to the extent that it does overcome the local station signals.
Did you take your voltage readings ahead of the VFD on the incoming supply? Did you change connections between starts? It is strange that two phases stay healthy but a different phase shows a drop on each trace.
Have you walked around the area with a small radio to find the area of greatest interference? Try near the VFD drive with the cover open and closed.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Cause of RFI during chiller compressor operation
Yes I did. Dranetz 658 power analyzer is curretly connected on 480V main to collect data. Data that you see on Chiller disconnect was captured on Dranetz Powervisa. Plan is to visit the facility after Thanksgiving when York folks return. Plan is to connect monitoring equipment at several locations to identify the cause. I can pick that up quickly. I'm hoping that this leads to cause of RFI but difficult to say right now.
No radio---When chiller starts-up basically there is so much RFI noise in the area (based on monitoring display on Radar Engineers Model 240 RFI locator) that entire parking lot area is buzzing so bad that you cant hear anything (AM reception is balanketed out for about 5-6 city blocks). No noise when the unit is shutoff-AM station nice, crisp-clear.
Plan is to check wiring connections starting from 480V Main-everything is suspect right now. Attached is the picture when I discovered someone had disconnected & taped the two ground conductors at main swgr neutral-ground bus. Ground wiring was re-connected back & tightened.
With respect to sag, I further reviewed the collected data, and there is indication that voltage drops to 250-300volts (from nominal 480volts) at no load. Pointing to the fact that something is wrong with supply voltage.
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RE: Cause of RFI during chiller compressor operation
When using a radio to hunt EMI you need to attenuated its ability to receive the signal. Wrap it in a Faraday cage or use one that's sheilded. You may need to even shield the antenna some. You want it compromised so badly that it can be used as a strength meter in your strong noise environment.
If you can get its sensitivity down far enough you should be able to work your way to the source.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Cause of RFI during chiller compressor operation
I think that this is not a VFD, rather it is a soft starter.
If it is in fact a soft starter (uses 6 SCRs) in series with the supply and no DC Bus capacitors, then it would normally make a burst of noise at start up and then go pretty quiet as the SCRs should be turned hard ON.
If it is a soft starter with an energy optimising option, then the voltage is reduced when the motor is under light load.
The energy optimizing option is not worth the trouble and is best disabled, that will reduce the SCR switching noise during run.
Your description sounds like conducted noise from SCRs that are being held in partial conduction rather than full conduction.
If it is a VFD, then the speed will change as the load is changed. If it is a soft starter, it will run at constant speed.
Best regards,
Mark.
Mark Empson
L M Photonics Ltd
RE: Cause of RFI during chiller compressor operation
The emitted noise is so strong that no matter which direction you point the RFI locator (or the portable radio) you will not be able to determine the source. But I understand your point.
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RE: Cause of RFI during chiller compressor operation
Mark, I have yet to see a York compressor with a soft starter. Could be, but I doubt it.
For OP: Is it a soft starter or is it a VFD?
I think that the 100 with no problem is more anectdotal than factual. Most VFDs produce EMI. But some areas are listening to AM radio and some aren't.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
Chiller is equipped water cooled SCRs. It is also equipped with harmonic filter package added (inductor coil & capacitor) . I will call to verify 100%.
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RE: Cause of RFI during chiller compressor operation
You now, again, say that you have SCRs. Inbetween you were certain it is a VFD. That is something that we need to be certain about if we shall progress at all.
I have been looking at your voltage recordings again, events #58 - 130 11/19/2009 15:17:12 - 15:19:11, and I am quite positive that this is not an actual problem with the grid or bad connection between grid and compressor. It cannot be anything but a loose connection in the measurement set up.
The reason I say so is that you can see very fast voltage edges and slow release when falling back to reduced voltage. This is what you get when you have a loose contact or bad cable between measurement point and measurement cable. What you see is voltage discharging (typical capacitance discharge curve) and then, when contact is established again, a very fast jump up to nominal sine value.
I think you shall review the 658 connections and also try to forget that you may have a problem with the grid or connection between grid and compressor. No compressor would continue operating when subject to disturbances like these. Most (all, I would say) drives would output alarms and stop operation on the first disturbance. That is obviously not happening and that is also an indication that you have to look for other explanations to your EMI problems than bad grid or grid connections.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
I apologize if I have caused any confusion.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Cause of RFI during chiller compressor operation
Is the required bonding from these conduits to ground missing?
RE: Cause of RFI during chiller compressor operation
Plan is to review collected data on 480V main, and compare with data collected on isolation transformer, and data collected on 480V chiller disconnect and check for any problems. Once I verify voltage stability on chiller disconnect, I can closeout the suspect on incoming service and focus on chiller end.
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RE: Cause of RFI during chiller compressor operation
Providing power quality solutions that empowers you!!!
RE: Cause of RFI during chiller compressor operation
What with bits of PVC inserted into conduit runs, no bonding of the conduits to the padmount (as reddog says) it seems that the installation needs a complete inspection.
You say a big voltage drop on startup-does that mean the lights in the school building actually flicker? It seems that the school is fed via the second dry-type transformer at 120/208V...readings taken with the Dranetz or other digital meters can be far off due harmonics. It may be old-fashioned but try an old moving-iron voltmeter instead.
Meters such as a Simpson or AVO usually are rectifier type and will show errors on heavily distorted waveforms. By several percent.
Try direct connecting the chiller via temporary cables laid on the ground directly to the 480V board, as a test.
I still feel that there is some HF coupling between the overhead conduits and the roof or steel trusswork in the building. You may have a giant antenna operating at a low
level of HF voltage but of immense area. Maybe you can get a patent on this...
Get the power company to inspect the HV side of the padmount-are the cable shields grounded and where..
If the bldg has not a metal roof, it can be the wiring on the 120/208V side is radiating. Did they use metal conduit or non-metallic?
just some more thoughts..
regards, rasevskii
RE: Cause of RFI during chiller compressor operation
Keep in mind that equipment manufacturere had implemented 10 different line item in order to suppress the RFI, and none worked. So, I have to bring back to code as required.
The roof is sheetmetal roof. With respect to utility padmount, primary concentrics are bonded to ground rod at 500kVA service transformer, system neutral goes from the padmount to 480V swgr bus ground connection, bonding jumpers installed between swichgear GRND and incoming neutral. In previous life I was a utility power line investigator doing all sort of power investigation/RFI/TVIs, can tell you service side has a question with respect to loading but I need little more field data to prove the facts. Typically the goal is to clean things first, let the dust settle and then see what else is left to go. Appreciate the comment.
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RE: Cause of RFI during chiller compressor operation
I just learned a few minutes ago that when a portable generator was brought in to power the 480V chiller disconnect (from 3-phase delta generator) the RFI was completly eliminated-gone(with 480V service & equipment ground disconnected from 480V main panel). Generator was then removed, isolation transformer was installed and noise was back in. It appears RFI could be related to 480V panel.
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RE: Cause of RFI during chiller compressor operation
A tough nut to crack, this. Looks like a lot of galvanic paths may exist between the infamous conduits and the roof.
Maybe a conn. at floor level would help...Conduits entering the top are hard to seal against water, anyway.
Perplexing...
rasevskii
RE: Cause of RFI during chiller compressor operation
Providing power quality solutions that empowers you!!!
RE: Cause of RFI during chiller compressor operation
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Cause of RFI during chiller compressor operation
Glad you got to the bottom of it.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Cause of RFI during chiller compressor operation
First inspection on bonding jumper way in the back of the 480Vswitchgear, with safety gloves pulled on system neutral and all connections looked tight at first glance. Checking the voltage increase to 529volts and decreasing to 250-350volts I figured system unbalance is due to bad neutral-ground bonding connection (which I always get that on power monitor), so I went back to double check this time with a lug driver. The bonding jumper was less than adequately tight- about 3/4 of a turn. For some reason this year I had 5 chiller cases, but this one was a odd ball. Thanks.
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RE: Cause of RFI during chiller compressor operation