Thanks Thanks:  0
Likes Likes:  0
Needs Pictures Needs Pictures:  0
Picture(s) thanks Picture(s) thanks:  0
Results 1 to 12 of 12

Thread: Dust and VFD's

  1. #1
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,541

    Default Dust and VFD's

    Seeing BobL's Linisher http://www.woodworkforums.com/showth...68#post1767768 has me wondering what people do about VFD's and dust. Industrially they are put in cabinets although that could be more a physical protection thing, but for home use what do people do? I have to mount one soon for the grinder and am debating either

    • putting it on a post and let it take it's chances
    • putting it in an enclosure (but then ventilation becomes an issue). Reading the specs, the clearances make the enclosure way big
    • putting it in a duct/ chimney so that dust can't fall directly on it but heat can be convected away


    My workshop is mixed, so there is metal dust (and grinding dust) as well as wood dust and all the other things that are found in garages

    Michael

  2. #2
    Join Date
    Nov 2005
    Location
    adelaide
    Posts
    597

    Default

    i have 3 vfd's so far no troubles left in the open but i reckon it will only be a matter of time before they need de- dusting . eg have a look in side a computer it seems to attract very fine dust. each enviroment is going to be different so a can of pressurized air duster is probably needed even in normal room situations (office works has it ) or maybe a blast with compressed air every now and then will do ( not too high a pressure) high dust areas i would think some air filtering would be neccessary
    john

  3. #3
    Join Date
    Nov 2008
    Location
    Perth WA
    Age
    71
    Posts
    6,458

    Default

    I noticed during my numerous visits to BobL's that a VFD was mounted above his wood lathe. I asked Bob about the lathe generated dust and whether it was a concern. It wasn't because Bob has an efficient dust extraction system in his shed. That efficient that dust doesn't affect the VFD.

    I intend mounting the T and C 's VFDs in the grinder's base, out of harm's way but grinding dust will require extraction. Bob's thread on dust particles and lung absorption stresses the importance of its removal.

    The 13 should have 3 VFDs (main motor, rapid feed and coolant pump) and my intention was to mount them within a clear doored, ventilated plastic enclosure. The enclosure is still in its cardboard box amidst the midden on my bench.

    Open eaves in the shed and property subdivisions ensure a pretty dusty shed environment even before I switch on any machine. It will be interesting to hear how others cope with dust Michael.

    BT

  4. #4
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,182

    Default

    Quote Originally Posted by Michael G View Post
    Seeing BobL's Linisher http://www.woodworkforums.com/showth...68#post1767768 has me wondering what people do about VFD's and dust. Industrially they are put in cabinets although that could be more a physical protection thing, but for home use what do people do? I have to mount one soon for the grinder and am debating either

    • putting it on a post and let it take it's chances
    • putting it in an enclosure (but then ventilation becomes an issue). Reading the specs, the clearances make the enclosure way big
    • putting it in a duct/ chimney so that dust can't fall directly on it but heat can be convected away

    My workshop is mixed, so there is metal dust (and grinding dust) as well as wood dust and all the other things that are found in garages
    Michael
    With regards the linisher.,that is why I'm going to put considerable effort into dust extraction on both the belt and the disc.

    The VFD on my MW lathe is in an enclosure but that has a fan in it so it's not like it's immune from shed dust.
    Generally that is not on when dust is happening elsewhere in the shed.

    On my wood work lathe (which can generate a large amount of dust) the VFD is located like on the linisher i.e. on a post above the machine like this.


    When I use the WW lathe that sucker behind the chuck pulls 1000 cfm from an open doorway 4 m behind me. Using a particle counter I have measured the dust levels where my head is and the fine dust levels are the same as outside my shed.
    The dust coming out of the air outlets of the the VFD are the same indicating that the VFD is effectively cooling itself using external air.

    Drilling is a different matter.
    I don't have dedicated ducting setup for my DP (yet) and if I want direct dust collection I have to pull off a couple of 100 mm ducts from the nearby bandsaw and hang these near the drill table. If things are set up right drilling makes relatively little fine dust and because of this there is a tendency for me not to bother with dust collection every time I drill. But there is no doubt that the VFD fan will suck in fine dust if nothing is done about it. It only takes 1 x 100 mm duct to easily draw the fine dust away from the VFD and that is probably what I will eventually plumb in permanently.


    As far as the VFDs are concerned I am more worried about grinding dust than wood dust and for that I have a reasonably beefy fume hood extractor which helps keep the air clear in the metal work end of the shed.
    I just have to remember to turn it on!

    Enclosures are not really a final solution for this either. Have you noticed how the very finest still seems to get into enclosures? This happens due to natural variations in air pressure so all cupboards/ecnclosures breathe to some extent and because the finest dust behaves like a gas it get's sucked in and out of enclosures. Inside the enclosures the air can be quite still so eventually the fine dust has a chance to settle out.

    Like tani51 I expect sooner or later one will go south but I put that down to the cost of having an interesting shed.
    Attached Images Attached Images

  5. #5
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,182

    Default VFD cooling

    The VFD on the Linisher is a 3kW jobbie and interestingly has no internal fan but an external one attached to a big heat sink.
    It's obviously relying on straight convection to cool the remaining internals

    Attached Images Attached Images

  6. #6
    Join Date
    Aug 2007
    Location
    Melbourne
    Age
    68
    Posts
    1,410

    Default

    Micheal, in my opinion the only safe thing to do is to install the VFD inside an enclosure. Dust entering the VFD via the ventilation slots can considerably shorten the life of a VFD. Cement dust with moisture will cause corrosion of the printed circuit tracks and component wires. Excessive wood dust with moisture creates a fire hazard within the VFD. Metal dust from grinding can cause short circuits when moist. Metal chips falling into the VFD can cause am instant short. So can water based coolant.

    The installation manual will tell you how big the enclosure must at least be, when no ventilation is provided. The enclosure can be a lot smaller, if you provide for ventilation. For example you can install a small box fan, that expels air from the top side of the cabinet. And on the opposed side of the cabinet towards the bottom you make an opening that lets fresh air be sucked in through a filter mat or a fine mesh. Of course the fan needs a power supply, so the advantage of a smaller enclosure comes at the expense of more complexity. Also you may want to add a window to the enclosure, such as to see the VFD display.

  7. #7
    Join Date
    Oct 2010
    Location
    melbourne, laverton
    Posts
    1,910

    Default dust

    A while back i had a melt down on a 2.2kw vfd.
    I assume that it was caused by dust.I didn't take any precautions to stop it
    I have been planing on housing the replacement vfd in a elecrical
    inclosure with filtered cabinet fan but as yet have not.
    External heat sinks are hany for dust profing your vfds but the front side of
    the vdf will probably still need some air flow.
    aaron

  8. #8
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,182

    Default

    It depends on the amount of dust in the area being worked in but as soon as as an enclosure fan is used that is almost as bad as not using an enclosure. The fine dust I'm talking about goes straight through most filters and grilles so they don't help that much. If the area has a high dust load, one way to deal with that would be to run a fresh air duct from outside and positively pressure the enclosure.

  9. #9
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,541

    Default

    And here's me thinking that this was a straight forward question...

    The VFD I have has a small fan on the heatsink, so there will be some forced convection. I was thinking about doing a half and half job - putting the heatsink part of the VFD through the back of the enclosure and then with some louvers or similar allowing the rest of the unit to convect naturally.
    As Bob is suggesting, the really fine dust gets everywhere. I can accept that this may get in to any enclosure I use. My main concern at the moment is to avoid dust that may drop the efficiency of the heatsink down or (in the case of metal dust) deposit on components such that insulation is rendered in-effective.

    Michael

  10. #10
    Join Date
    Aug 2007
    Location
    Melbourne
    Age
    68
    Posts
    1,410

    Default

    A ventilated enclosure will not work where large amounts of fine dusts are present (wood sanding dust or cement dust come to mind). An IP65 or IP66 enclosure is needed. I can see four options:

    1 - Where money does not matter, some VFD's can be bought from the maker ready installed into a small, sealed, ribbed on the outside, die cast metal enclosure, including IP66 proof switchgear on the front panel. Unfortunately cost is 2-3 times the price of the equivalent "naked" VFD. This is no doubt the smallest and most convenient option. Overall size is only slightly larger than the naked VFD, because the IGBT transistors are mounted directly to the enclosure. The maker guarantees the IP rating of the whole system.

    2 - An IP66 steel enclosure large enough to dissipate the heat by passive convection alone can be used. The VFD installation manual states the minimum size of such enclosure. Cables must enter it via proper IP66 glands, any switchgear to the front panel must be IP66 proof too. However, not everywhere such large enclosure can be used, and large metal enclosures can cost as much as a VFD. Heat radiated by the VFD heat sink is moved by the air inside the cabinet (by convection and helped by the small VFD fan) and transferred from the inside to the walls of the cabinet. The outside walls transfer this heat by convection and radiation to the ambient air. The key for this process to work is a sufficient area of the enclosure walls in relation to the heat generated by the VFD, and the higher the ambient temperature the more area is needed.

    3 - A DIY alternative to keep an IP66 enclosure size small is to increase the area of the enclosure side walls. This can be achieved by installing ribbed heat sinks to both sides, with heat compound paste in between. An additional fan to circulate air inside the enclosure may be needed too.

    4 - Another DIY method to keep IP66 enclosure small is to install a ribbed head sink to the rear of the enclosure, and mount the VFD from the inside directly onto iy using heat transfer compound. The enclosure must however remain IP66 proof.

    Alternative 1 is 100% foolproof.

    Alternative 2 is foolproof if sized to the VFD maker's size table according to the highest expect ambient temperature. Just note it must be a metal enclosure, not plastic.

    Alternatives 3 and 4 depend on some common sense when designing. Probably a good idea to check inside temperature during the first weeks of use.

  11. #11
    Join Date
    Jun 2011
    Location
    Australia east coast
    Age
    71
    Posts
    2,713

    Default

    Quote Originally Posted by cba_melbourne View Post
    1 - Where money does not matter, some VFD's can be bought from the maker ready installed into a small, sealed, ribbed on the outside, die cast metal enclosure, including IP66 proof switchgear on the front panel. Unfortunately cost is 2-3 times the price of the equivalent "naked" VFD. This is no doubt the smallest and most convenient option. Overall size is only slightly larger than the naked VFD, because the IGBT transistors are mounted directly to the enclosure. The maker guarantees the IP rating of the whole system.
    I bought 2 NIB Danfoss units in very nice IP66 housings some years ago at a price where the money really didn't matter....

    They're still sitting on the floor waiting for their turn, seeing as they need some form or RS485 control system and I simply can't be bothered ATM.

    PDW

  12. #12
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,541

    Default

    Quote Originally Posted by cba_melbourne View Post
    A ventilated enclosure will not work where large amounts of fine dusts are present (wood sanding dust or cement dust come to mind). An IP65 or IP66 enclosure is needed.
    That's the rub. According to the manual an enclosure for the VFD I have must be at least 450mm high although only 185 wide and 127 deep. That is a lot of height (x3 the VFD height), and the reason I was wondering about mounting in a duct or (latest thought) mounting in a smaller enclosure that has a removable top and bottom (for example, mount the VFD on the lid and hinge the box away as a door) so that in use it is effectively in free space but when powered down is covered.


    Michael

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •