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Thread: 3 Phase motor noise?

  1. #21
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    Jan 2014
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    Edmonton Alberta
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    I would also check the belt.

  2. #22
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    Aug 2009
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    What noise are you referring to?? I hear several different noises in the video. Whining, buzzing, clunking and some chatter. Which is it?
    Sounds like it's coming from the head of the machine.

    JL.............

  3. #23
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    Feb 2019
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    Wisconsin
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    The main thing I was trying to fix was the electronic wine coming from the motor, that is the whining and buzzing sounds you are hearing. Raising the carrier frequency has eliminated 90% of that.

  4. #24
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    Feb 2019
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    Wisconsin
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    So I looked in the the rattling noise some more, couldn't find anything obvious that is making the noise. It was not the draw bar. Only thing I found that was mentioned in the book is that as the clutch wears you have to adjust the detent plate on the high lower lever to make sure it is engaged all the way or you will get clutch rattle. We I tried adjusting and actual found that I can not get neutral at all in the detent where it is suppose to be, I have to manually hold the lever part way back to get it into neutral. It is engaging high all the way but I wonder if the clutch is worse past being able to adjust it correctly?

  5. #25
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    Mar 2015
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    It is very easy to forgive other noises when you have a noisy VFD setup. Noisy VFD is enough to want you to walk out of the shop, turn off the lights and go watch a movie instead. High pitch whiny electrical noise that changes in pitch with speed is no way to enjoy machining.

    Sent from my SM-G950U1 using Tapatalk

  6. #26
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    Aug 2004
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    Quote Originally Posted by lakeside53 View Post
    Not the VFD... the motor is affected by the higher carrier frequency. Goggle is your friend.
    So the carrier is transmitted to the motor? Seems like some filtering might help no? Seems the carrier should be of low power so as to not tear the motor apart. JR
    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  7. #27
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    Oct 2013
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    The carrier, typically about 10 kHz, constantly switches between about 350 volts to zero, with pulse width variation from less than 100 uSec to 10 mSec, with rise and fall time in the order of 1 uSec, so there can be frequency components in the MHz range. Without filtering, these transients will cause significant current flow through the insulation of the wires going to the motor, and through the insulation of its windings, and to ground. The current can flow through the bearings and cause pitting and premature failure. You can probably make a reasonable filter by wrapping a few dozen turns of wire through an old transformer core, perhaps 50 watts or so (3-4" cube). It might need a magnetic gap, which can be provided by cutting through the laminations with a band saw.

    Some more information, although some are perhaps too technical for non-EEs:

    https://www.mtecorp.com/pages_lang/w...-Solutions.pdf

    https://pdfs.semanticscholar.org/48c...460735c6ad.pdf

    http://irdindia.in/journal_ijaeee/pdf/vol3_iss3/3.pdf

    http://sgemfinalreport.fi/files/06244870.pdf

    http://www.eprojectszone.com/lowpass...ine-inverters/ (More oriented toward DIY projects)

  8. #28
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    May 2011
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    Surrey, England
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    I built three separate inductors ("load reactors") for the three phases, mainly because my Holbrook has an unique and irreplaceable motor (3-speed, size of a dustbin with 1950's insulation...) - I used three (identical) surplus control transformers rewound with 1.5mm enamelled copper, I *think* I needed about 100 turns (it was a while ago) to get the right impedance, worked out by taking the full load current and aiming for about 5% of the applied voltage being dropped at 50 Hz.

    Because that's the way inductors work, the impedance scales with frequency, so 500 Hz sees 10x the impedance, 5 KHz sees 100x, the harmonics / rising/falling edges are attenuated and the motor's protected.

    To get the magnetic gap (prevents magnetic saturation in the core) I dismantled the core, reassembled with all I laminations at one end, all E at the other and put a thin PTFE shim in between to maintain it.

    I measured the inductance with a complicated signal generator / oscilloscope setup, have since bought a cheap LCR meter and they seem to agree?

    They seem to work well, as the Holbrook has winding / pole switching between the VFD and motor I've interlocked the speed change lever with the fwd/rev drive to the VFD logic inputs and added some varistors (VDRs) to the motor side of the switches ("downstream" of the inductors) in case of any spikes from the motor inductance (planned maintenance is replacement, probably annual as they do "wear out" when subjected to spikes) - haven't killed motor or VFD yet, fingers crossed!

    Dave H. (the other one)
    Rules are for the obedience of fools, and the guidance of wise men.

    Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

  9. #29
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    Nov 2007
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    Woodinville, WA
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    Quote Originally Posted by JRouche View Post
    So the carrier is transmitted to the motor? Seems like some filtering might help no? Seems the carrier should be of low power so as to not tear the motor apart. JR
    That's why they sell "output inductors" (common in industrial installations, commonly ignored by HSM ). Literally filters the output back to a "sine wave". $50-150 for nice purpose-built device. Be sure to size it right and choose either 3 or 5% impedance.

    example (can be used as Load OR Line) :
    https://www.galco.com/buy/MTE/RL-008...xoCz48QAvD_BwE

    I first look for them on ebay and other places.
    Last edited by lakeside53; 08-18-2019 at 12:02 PM.

  10. #30
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    Mar 2010
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    Quote Originally Posted by lakeside53 View Post
    That's why they sell "output inductors" (common in industrial installations, commonly ignored by HSM ). Literally filters the output back to a "sine wave". $50-150 for nice purpose-built device. Be sure to size it right and choose either 3 or 5% impedance.

    example (can be used as Load OR Line) :
    https://www.galco.com/buy/MTE/RL-008...xoCz48QAvD_BwE

    I first look for them on ebay and other places.
    Modern small motors with short leads between VFD and motor as used in a typical HSM shop do not need reactors. The motor's inherent inductance is a very good filter. If you look at the current waveform, it is a pretty good sinewave. The PWM algorithm is designed that way because the motor's magnetic circuit wants to see a sinewave for best performance. The insulation systems in modern motors are always epoxy or polyester impregnated and are very resistant to voltage transients, vibration, and overheating. If your motor is making electrical noise, adjust the carrier freq. and it will normally go away. That is why the carrier freq. is adjustable.

    Industrial applications are another ball game entirely. Reactors are sometimes used to suppress long lead standing waves( Google it).], but modern motors are resistant to the problem as they are. The plant I retired from had about 300 VFDs from 1 to 700 HP ( all 460V) and there were no reactors used. They would have certainly been used if there had been a demonstrated benefit since reliability was the single most important aspect of the electrical system.

    RWO

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