Page 2 of 3 FirstFirst 123 LastLast
Results 16 to 30 of 31
  1. #16
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Bob,

    Quote Originally Posted by BobL View Post
    This week I'm going to be giving a general live video presentation about VFDs to WA mens Sheds Association so if its OK with you I would like to sue that diagram in my presentation. My talks is more about applications but I thought I would start of with a few minutes of intro of a "hand waving this is how they work" .

    Cheers Bob
    Be my guest, but SUE me, no thanks
    Best Regards:
    Baron J.

  2. #17
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Mal, Guys,

    Yes I agree with your comments about the centrifugal switch in the starting circuit. You would have to test your particular motor to ensure that you couldn't run it or load it enough for the switch to drop out at low speeds. You would also need to make sure that you couldn't try to start it at a low speed either.

    They seem to open the CF switch at about 80% of nominal speed and close at around 50% of nominal running speed. That would be about 2300 rpm before it opens. I've had a 1Hp single phase induction motor running at 75Hz about 4000 rpm, but it got hot a lot more quickly. Split Phase, capacitor start and run motors like they use on shower pumps do a lot better.
    Best Regards:
    Baron J.

  3. #18
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    I realise there are thousands of existing SP motors around that could use speed control but in an interesting discussion I had recently with my cousin, who makes electric motors, many with built in VFDs, he reckons in terms of new motors its just not worth messing about with SP motors and sees 3P motors with VFDs eventually replacing SP motors in many applications. One of the drivers for this is stiffer EU requirements for energy efficiency and he is required to make all his motors more and more energy efficient. I guess millions of small SP motor operating at say 75% versus say 80% adds up to a lot of Watts. He says SP motors will eventually become the incandescent light globe of motors.

  4. #19
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
    Posts
    1,407

    Default

    As a matter of interest, one of the Australian electronics mags some years ago published a design for a single phase VFD to suit swimming pool pump motors. The idea was to save power charges as the pump didn't need to run full bore all the time, and the payback period was short enough to make it worthwhile. The designers were quite specific that this VFD was only for motors with no start winding switches, and if I was home at the moment I would be able to include more details as I would have the Magazine and could include a photo of the specs and design synopsis from it. I would not be surprised if current Jaycar catalogues still had kit details, if not some of the older ones certainly do. When I get home in a few days I can dig up more details if anyone is interested.

  5. #20
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Rob, Guys,

    Quote Originally Posted by Ropetangler View Post
    As a matter of interest, one of the Australian electronics mags some years ago published a design for a single phase VFD to suit swimming pool pump motors. The idea was to save power charges as the pump didn't need to run full bore all the time, and the payback period was short enough to make it worthwhile. The designers were quite specific that this VFD was only for motors with no start winding switches, and if I was home at the moment I would be able to include more details as I would have the Magazine and could include a photo of the specs and design synopsis from it. I would not be surprised if current Jaycar catalogues still had kit details, if not some of the older ones certainly do. When I get home in a few days I can dig up more details if anyone is interested.
    That would be interesting, to me at least !
    Best Regards:
    Baron J.

  6. #21
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Bob,

    I tend to agree with your cousin, a lot of the motors that I'm seeing today tend to be three phase VFD driven and BLDC ones that don't have field coils, so much less copper in them. Though a couple that I've taken apart recently had aluminium windings in them, no copper at all.
    Best Regards:
    Baron J.

  7. #22
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
    Age
    56
    Posts
    1,185

    Default

    Quote Originally Posted by morrisman View Post
    When a wire wheel is mounted on the average bench grinder, It would be handy to control the speed of the grinder to some degree for some jobs
    1) Another way is to use different machines. I use 1.25" wire brushes in a Dremel to clean up rusty old drill flutes.
    I have also been slowly collecting a few different old grinders for just this purpose. A weak little 5" Black & Decker for light polishing, a 6" with a nylon+grit wheel for de-rusting, and an 8" with an inch wide wire wheel for cleaning large threads, taps, et c.

    2) In terms of safety, I always try to stand beside the grinder, so the ejected bits of wire do not end up in my hands/arms/chest/face.
    (I also usually wear gloves, but that is more to limit grit insertion than to stop high-speed hypodermics)

  8. #23
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    Quote Originally Posted by nigelpearson View Post
    1) Another way is to use different machines. I use 1.25" wire brushes in a Dremel to clean up rusty old drill flutes.
    I have also been slowly collecting a few different old grinders for just this purpose. A weak little 5" Black & Decker for light polishing, a 6" with a nylon+grit wheel for de-rusting, and an 8" with an inch wide wire wheel for cleaning large threads, taps, etc
    In related way I have been using Scotchbrite wheels for about 8 years and now have a selection of different sizes - from 8" down to 3". I always use the large sizes but SWMBO and mates are more comfortable at using the smaller ones.

  9. #24
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Bob, Guys,

    These Scotchbrite wire wheels in my opinion are much safer and nicer to use than a steel wire wheel.

    scotch-britetm-radial-bristle-brush-ta.jpg
    Best Regards:
    Baron J.

  10. #25
    Join Date
    Jul 2008
    Location
    near Warragul, Victoria
    Posts
    3,718

    Default wheel side

    Using the side of the wheel is considered to be dangerous by many . I tried a technique that seems to be effective. I turn the grinder on and as the wheel is gaining RPM's , turn it off again I use the side of the wheel for a light touch up on a HSS lathe tool. The timing takes a little getting used to but after a while the method is good .

  11. #26
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Morrisman, Guys,

    For thin wheels I would agree ! However most DE grinders have wheels 3/4" to 1" inch thick, unless you have replaced them with thinner ones, for the amount of touch up grinding that an HSS lathe tool takes, I'm of the opinion that it matters little. There is more wear and tear on the motor and its components switching it on and off like you suggest.

    Anyway if you are shaping a piece of HSS for some purpose, you would use the face edge of the coarse wheel !
    Best Regards:
    Baron J.

  12. #27
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    Quote Originally Posted by BaronJ View Post
    Hi Bob, Guys, These Scotchbrite wire wheels in my opinion are much safer and nicer to use than a steel wire wheel.

    I'm a big fan of 6 or 8 fold Scotchbrite wheels which can tackle a wide area in one pass.
    Plus the folds can get down inside grooves and gaps.
    This is an 8 fold wheel I made by combing from 2, 4 fold wheels.
    Yes, on assembly it is uneven but it wears flat fairly quickly
    IMG_3389p.jpg
    They cost a fair bit and only last me for about 2 years then it gets too small for me but SWMOB will use it for a couple of years after that.
    For thread like gaps a wire wheel is hard to beat.

    Quote Originally Posted by morrisman View Post
    Using the side of the wheel is considered to be dangerous by many . I tried a technique that seems to be effective. I turn the grinder on and as the wheel is gaining RPM's , turn it off again I use the side of the wheel for a light touch up on a HSS lathe tool. The timing takes a little getting used to but after a while the method is good .
    Depends on the wheel, if the abrasive is fixed to the outside if a steel wheel (as in diamond or CBN wheels) then this is not a problem.

    Screen Shot 2020-07-08 at 6.36.27 am.png

    I have two of these wheels plus a diamond wheel and no longer have any standard abrasive wheels in my shed. If I want to do some heavy grinding I use 40 grit on a belt sander.

  13. #28
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

    Default

    So those scotchbrite wheels come with 4 layers Bob?

    Are they genuine 3M ones, or just generics?

    Steve

  14. #29
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    Quote Originally Posted by OxxAndBert View Post
    So those scotchbrite wheels come with 4 layers Bob?

    Are they genuine 3M ones, or just generics?

    Steve
    These are generic but I have bought 3Ms when I can find them but there's not many available that I have been able to find lately.

    I like to use 8" as they are the best value for available surface are.
    Every time I go to buy them the availability, size and numbers of layers seems to change.
    Sometimes I get a pair of 3 or layers and combine them.
    Sometimes if I can find them I get a 6 layer.

    Usually I order from this site
    https://abtoolsonline.com/search-res...chbrite&page=1

  15. #30
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
    Posts
    1,407

    Default

    Quote Originally Posted by BaronJ View Post
    Hi Rob, Guys,



    That would be interesting, to me at least !
    Well here you are John, BobL and anyone else interested, I finally found it. Silicon Chip still has a presence, and a website where reprints of past articles from their magazine and also several other now defunct Ausie electronics mags as well. (Electronics Today, Electronics Australia and their previous masthead, Radio, Television and Hobbies.) I will put a link up for anyone wanting to get more info, but here are a few pics from the magazine to provide a synopsis of the article.
    Silicon Chip Project Index - Silicon Chip Online Go down to section 10, Mains Power control to see the reference to this project. It appears that Altronics still supply kits for this project, but they are a bit spendy considering the low cost of commercial VFDs these days. https://www.altronics.com.au/p/k6032...ontroller-kit/
    I have tried unsuccessfully to add some photos of the introductory pages to the Silicon Chip project, and will have another try tonight, but I am otherwise occupied today and don't have time to fiddle with computers and finicky forum software.

Page 2 of 3 FirstFirst 123 LastLast

Similar Threads

  1. Hercus #3A or #1 T&C smaller wheel guard and Hercus #3A wheel shaft pulley.
    By lamestllama in forum METALWORK - Machinery, Equipment, MARKET
    Replies: 8
    Last Post: 30th Aug 2019, 12:01 PM
  2. Re purposing a pot as a wire wheel guard
    By bollie7 in forum METALWORK PROJECTS
    Replies: 9
    Last Post: 22nd May 2019, 10:05 AM
  3. VFD safety
    By BobL in forum ELECTRICALS
    Replies: 10
    Last Post: 5th Sep 2016, 09:40 AM
  4. safety video
    By welder in forum METALWORK GENERAL
    Replies: 12
    Last Post: 3rd Apr 2012, 09:55 PM
  5. Safety tip
    By .RC. in forum WELDING
    Replies: 2
    Last Post: 27th Jul 2009, 01:55 PM

Posting Permissions

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