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  1. #31
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by simonl View Post
    That's nice. I do like the sound of that too. I would be interested in your feedback as to whether you get a better finish with a 3 ph motor. I have read that you can improve the finish purely by changing from a 1ph to a 3ph motor because they are smoother in running. Not sure how true that is but I would be keen to see what you think.
    All things being equal I doubt this is the case from a pure 3P tp SP point off view. The rotational inertia of chucks, gears and pulleys on a lathe would smooth put any pure SP/3P differences and factors like speeds, bit choice, profile and setup, are going to be way more dominant in this space. Next would come things like lathe rigidity and vibe.

    The last point, vibe, is interesting. Most 3P motors tend to be better made than cheap SP motors so 3P motors have less vibe. After I started testing motors for vibe I've found that some cheap SP can be pretty crappy vibe wise otherwise a well made SP motor can be just as smooth as a 3P motor.

    As an example, when I converted my SP 3HP dust extractor to 4HP 3P, the SP motor without the impeller attached had more vibe than the 3P motor with impeller attached.

  2. #32
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    It sounds like a realistic argument Bob. That's why I started the sentense with "I have read" ! That was my disclaimer to saying I'm not sure how true it could be!

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  3. #33
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    Thumbs up Motor Vibration !

    Hi Guys,

    Has anyone noticed that single phase two pole motors vibrate more than the single phase four pole motors of the same size even without anything on the shaft ! And six and eight pole motors still less.

    Three phase motors should be even better than these under the the same conditions.

    Ignoring out of balance rotors, the vibration is caused by the fundamentally unbalanced magnetic forces acting on the iron work inside. Certainly with single phase motors that have more poles the magnetic fields are more and more balanced as the number of poles increases.
    Best Regards:
    Baron J.

  4. #34
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    Quote Originally Posted by BaronJ View Post
    Hi Peter,

    Looking good !

    I would not use silicon round that post ! I would use some felt or knitting wool pressed into the gap, then it can easily be removed if needed rather than trying to scrape away silicon filler full of chips.
    I was actually thinking of something like "no more gaps". It doesn't stick as well as silicon so easier to remove but I'll think about what you said. As its a hobby lathe I reckon if I end up working that fast that a lot of swarf is going up there, then I will obviously have to slow down a bit.

    Quote Originally Posted by BaronJ View Post
    Though about the only chips I can imagine getting up there, would be Brass. They seem to find their way into the most non intuitive places ! Having had to fight the zip on my jeans the other day
    That's almost a TMI moment.

  5. #35
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    Got the tacho working today. End up gluing the magnet to the change gear end of the spindle and made a bracket to hold the sensor.
    Whilst the display looks pretty, unfortunately I think its a dud. Readout fluctuates all over the place. reading say 380 rpm then jumping to 1400 rpm and back down to 600 etc.
    The laser hand held I have on loan atm is very consistent and I am inclined to believe it over the other one.
    When I got this early this year I tested it using my battery drill as the rotating part and I had all sorts of weird displays.
    I'm pretty sure I either put up a post on this forum about it or replied to one and someone with more knowledge of the dark art of electronics suggested I try a different power supply. Which I did at the time and that seemed to make it work ok.
    I've just been searching for at least 30 minutes to try and find those posts and I cant find them.
    Today I have tried 3 different power supplies with the same results with all of them

    This is the unit I have
    4 Digital LED Tachometer RPM Speed Meter + Proximity Switch Sensor NPN

    which I bought from Banggood for the eye watering price of around $14aud at the time.
    If anyone has any suggestions I'd be most grateful to hear them.
    Peter

  6. #36
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    Another thing I noticed today is that the motor has a bit of a whine to it. I only noticed it when I dropped something and bent down to pick it up (thus having my head closer to the motor).
    I remember when I first played around with the Huan Yang on my Mill motor that it whined at first. After a couple of years I have no idea what parameters I changed that stopped the whine.
    Now that I know its there, I can hear it (just), when the motor is running. I can live with it but I dont know if its something that could damage the motor or VFD.
    I've been doing a bit of research just now and it appears the "carrier frequency" of the VFD might be causing it.
    Of course in the HY book I cant find a mention of the "carrier frequency" as such but it does mention "Motor rating frequency" on PN12. Its too late for me to go and check what this is set at just now though
    I'm not game to try changing this atm. So again any input from the Gurus would be greatly appreciated.
    thanks
    Peter

  7. #37
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by bollie7 View Post
    Got the tacho working today. End up gluing the magnet to the change gear end of the spindle and made a bracket to hold the sensor.
    Whilst the display looks pretty, unfortunately I think its a dud. Readout fluctuates all over the place. reading say 380 rpm then jumping to 1400 rpm and back down to 600 etc.
    The laser hand held I have on loan atm is very consistent and I am inclined to believe it over the other one.
    When I got this early this year I tested it using my battery drill as the rotating part and I had all sorts of weird displays.
    I'm pretty sure I either put up a post on this forum about it or replied to one and someone with more knowledge of the dark art of electronics suggested I try a different power supply. Which I did at the time and that seemed to make it work ok.
    I've just been searching for at least 30 minutes to try and find those posts and I cant find them.
    Today I have tried 3 different power supplies with the same results with all of them

    This is the unit I have
    4 Digital LED Tachometer RPM Speed Meter + Proximity Switch Sensor NPN


    which I bought from Banggood for the eye watering price of around $14aud at the time.
    If anyone has any suggestions I'd be most grateful to hear them.
    Peter
    I have 4 of those tachos on my machinery.

    One thing with the ones I have is that although they say they will work on 8 - 24V that is only the case using my stabilised power supply, or the 24V power line from a VFD, On simple DC power adapters they seem to work better around 12V.

    What you are describing suggests that either the magnet is too far from the sensors or the PS and sensor line has inadvertent been accidentally swapped over at some time. If you leave the PS on the sensor line for too long it can can damage the sensor especially if you are using higher PS Voltages.

    Cordless drills are not a good test bed as they use large currents and output a high magnetic fields which will mess with the sensor. A better rotary testing device is a simple fan.

  8. #38
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    Thanks for your advice Bob. As always I appreciate it.'
    Definitely wired correctly. However I was just reading a couple of reviews on a similar tacho on Amazon and a couple of people said the polarity of the magnet was important. This was for a different brand tacho and I didnt think it would matter as its basically just a switch, but still it might be worth investigating.
    I'll look at that tomorrow.
    peter

  9. #39
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by bollie7 View Post
    Thanks for your advice Bob. As always I appreciate it.'
    Definitely wired correctly. However I was just reading a couple of reviews on a similar tacho on Amazon and a couple of people said the polarity of the magnet was important. This was for a different brand tacho and I didnt think it would matter as its basically just a switch, but still it might be worth investigating.
    I'll look at that tomorrow.
    peter
    Yes magnet polarity is definitely important.

  10. #40
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    Hi Peter, Guys,

    I agree with Bob completely ! Magnet polarity is important. Hall devices can behave quite differently if the magnet polarity is not what they expect. However some of the inductive sensors don't seem to mind either way.

    One other thing that sometimes screws things up, is gear teeth ! If the magnet is in between or close to gear teeth the sensor sees the teeth and counts them. That can get very confusing !

    The cure there is to move the magnet away from the teeth and adjust the sensor distance.

    With respect to motor whine, just up the carrier frequency until you don't hear it !
    Best Regards:
    Baron J.

  11. #41
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by BaronJ View Post
    With respect to motor whine, just up the carrier frequency until you don't hear it !
    The Powtran Manual has a some useful info for users that want to change their VFDs carrier freq.


  12. #42
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    Couple of things that I have experienced with these tacho systems, they can be suseptable to electrical noise from the VFD. I ended up putting a 0.1uf mkt capacitor from the sensor input to ground in order to filter out the high frequency noise.it did the trick.

    I have also had issues with sensors (magnetic and inductive) not having a high enough response frequency and not working and giving erratic readings after a certain speed.

    The motor whine is most definately the carrier frequency. My cheaper VFD does not have any way to change the carrier frequency. Not sure if yours does.

    Simon

    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  13. #43
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    Quote Originally Posted by bollie7 View Post
    Got the tacho working today. End up gluing the magnet to the change gear end of the spindle and made a bracket to hold the sensor.
    Whilst the display looks pretty, unfortunately I think its a dud. Readout fluctuates all over the place. reading say 380 rpm then jumping to 1400 rpm and back down to 600 etc.

    Peter


    Hi Peter,

    I had exactly the same problem with the two tachos I set up on my wood lathes, I had originally made the the brackets to mount the sensors out of ali and the readout was all over the place. I remade the brackets out of plastic and now they are stable

    Regards

    Rick

  14. #44
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    Quote Originally Posted by warrick View Post
    Hi Peter,

    I had exactly the same problem with the two tachos I set up on my wood lathes, I had originally made the the brackets to mount the sensors out of ali and the readout was all over the place. I remade the brackets out of plastic and now they are stable

    Regards

    Rick
    Rick. That's interesting. I've mounted mine using an aluminium bracket, inside the change gear cover which is made from cast aluminium.
    When I first got mine I tried it out using a battery drill as a source of variable speed. BobL reckons that might not have been such a good idea.
    I have two of these so I think I'll put some time in and set one up a bit better for testing.
    peter

  15. #45
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    Quote Originally Posted by simonl View Post
    Couple of things that I have experienced with these tacho systems, they can be suseptable to electrical noise from the VFD. I ended up putting a 0.1uf mkt capacitor from the sensor input to ground in order to filter out the high frequency noise.it did the trick.
    I might have to try that. However I'm going to set the other one I have up properly - maybe on my drill press to see how it goes.

    Quote Originally Posted by simonl View Post
    I have also had issues with sensors (magnetic and inductive) not having a high enough response frequency and not working and giving erratic readings after a certain speed.
    If it's going to get that complicated I might just buy a hand held one like the one I have on loan atm.

    Quote Originally Posted by simonl View Post
    The motor whine is most definately the carrier frequency. My cheaper VFD does not have any way to change the carrier frequency. Not sure if yours does.

    Simon

    Sent from my SM-G970F using Tapatalk
    I haven't found anything in the user book that specifically refers to it, unless the engrish is calling it something else. I can live with the noise as long as the motor is not going to be damaged.

    peter

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