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  1. #31
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    Quote Originally Posted by rtyuiop View Post
    ...And 3 phase outlets and gear aren't all that cheap...
    Fair comment. You have to do what you're comfortable with (and noting the Ubeat disclaimer on electrical advice).

    But I'll say that my PDL/Clipsal plugs (and cord connector for the extension lead) were all purchased via Trademe at prices between $15 and $30 NZD - with the average around $25. I use 32amp (although the biggest draw on any of my 3-phase machines is less than 10amps per phase) because they seem to be the most available. The most expensive thing was the 7m cord which, from memory, cost ~$85 three years ago (new from a local electrical wholesaler).

    Every plug was completely stripped down and cleaned (by me). I made sure the brass contacts were shiny, before re-assembly.

    If I was re-powering any heavy machine and had to choose between single or 3 phase, I'd select 3-phase every time. I believe 3-phase motors are simpler, and more robust.

    Cheers, Vann.
    Gatherer of rusty planes tools...
    Proud member of the Wadkin Blockhead Club .

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  3. #32
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    This sander is 1.1kW so I don't see it as being any sort of a heavy machine.

    Any extension cords, let alone 3 phase cables, are problematic and it's all round safer to avoid or at least minimise their use. Yes ,they can be made safer by going long or high but then the cost of the cable increases and there's a chance it will get hidden in the process which has its own dangers. It's much better and safer to install a dedicated outlet as close as possible to where any machine is going to be used and for machines to have dedicated sockets.

    I agree that even branded 3P plugs are not that expensive and even 4 or 5 core cable is not that expensive here in Oz, but presumably the sander already has these so these are not the issue. What bites are the the branded sockets plus switches, plus cable, plus breaker - now they will really put a hole in your wallet. This is less of a problem if your sparky is satisfied with using unbranded products but my experience is that here is Oz they don't like or won't do that.

    Even if a sparky will install used or unbranded gear, a socket and switch, cable and a breaker (let alone the installation cost) may exceed the cost of a 2HP VFD that will run from any 10A GPO while offering other benefits. If the sparky knows what he's doing it should take less time to set up a VFD than install a breaker/line/socket and switch and he should charge accordingly.

    Our men's shed was quoted $500 to install a 3P socket/switch with a 14m cable run (there were already spare breakers in the breaker box) but fortunately our still licensed shed sparky said he would do it so the install cost was saved but I think he paid still $85 for the plug and switch and $50 for the cable. The 3P socket was installed right next to 4 unused 10A GPOs. 3 months later the machine was moved to a different location in the shed sand now share a 3P socket with another heavily used machine so that their plugs are constantly being swapped in and out dozens of times a day - also not best practice.

  4. #33
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    Quote Originally Posted by BobL View Post
    Either your sparky doesn't want to get involved or doesn't know much about VFDs but that is definitely a convertible motor (I have a similar WEG 3kW motor on my DC but mine isa 2850 rpm - 2 pole motor).
    Your motor is wired as a Y and it's just a matter of rearranging the brass connections between the terminals to convert it toe 240V ∆.

    It's a matter of rearranging the brass strips (there will be 3 of them) marked by the red marks and connecting them .
    Please don't attempt this yourself and get your sparky to do it.
    Attachment 456859

    These WEG motors are very common and widely used on water Pumps and fans with VFDs.

    I also notice your motor is 1430 rpm motor. In that case a VFD is really worth having so the speed can be boosted to 150 or 175% for belt work.
    Does the machine have a disc as well as a belt?
    Although you will have to be a bit more careful about not overheating the wood you'll find its MUCH faster with a fresh sanding belt than running at 1430.

    For shaping work I sometime run my 3HP sander up to 3200 rpm using zirconia belts - makes a lot of dust but fair rips things into shape.
    Yeah, I think there is a reasonable chance the sparky doesn't want the work, I'll see if his quote is competitive - if he doesn't want it, he'll just quote high and the question will be answered! Will not be touching any wiring myself - far too high a chance of either killing myself or letting the magic smoke out of something!

    This machine is a disc only (350mm). I am definitely keen on speed control - both to go faster and to slow it down for the occasional more delicate work.

    Cheers,

    Danny

  5. #34
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    Had a couple of sparkies come through yesterday to quote for this work (plus some extra lights and GPOs as I'm expanding the workshop) - that'll give me some idea of the relative costs of VFD vs. 3 phase.

  6. #35
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    Quote Originally Posted by rtyuiop View Post
    Yeah, I think there is a reasonable chance the sparky doesn't want the work, I'll see if his quote is competitive - if he doesn't want it, he'll just quote high and the question will be answered! Will not be touching any wiring myself - far too high a chance of either killing myself or letting the magic smoke out of something!
    Good move

    I suspect the sparkies will charge more for a VFD because they will want to use one they know about and that will take the purchase price of the VFD alone into the $500 RANGE

    This machine is a disc only (350mm). I am definitely keen on speed control - both to go faster and to slow it down for the occasional more delicate work.
    OK in that case you won't be wanting to use the higher speed for wood. It will be handy if you want to grind some metal.

  7. #36
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    Quote Originally Posted by BobL View Post
    Either your sparky doesn't want to get involved or doesn't know much about VFDs but that is definitely a convertible motor (I have a similar WEG 3kW motor on my DC but mine isa 2850 rpm - 2 pole motor).
    Your motor is wired as a Y and it's just a matter of rearranging the brass connections between the terminals to convert it toe 240V ∆.

    It's a matter of rearranging the brass strips (there will be 3 of them) marked by the red marks and connecting them .
    Please don't attempt this yourself and get your sparky to do it.
    I know bugger all about 3PH, but I thought to convert between 415/240 if it's supported, the nameplate needs to actually state both voltage/draw configurations?

    Or can all 3PH motors that support Star/Delta automatically work on 240V/Delta mode?

    cheers, Ian

  8. #37
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    Quote Originally Posted by aarggh View Post
    I know bugger all about 3PH, but I thought to convert between 415/240 if it's supported, the nameplate needs to actually state both voltage/draw configurations?
    The name plate is a good but imperfect guide
    - some nameplates claim conversion is possible but when the junction is opened the required bits are missing and VV.
    Most old 415V 3P Y connected motors can be converted to 240V by taking them to a motor rewinder who will swap a few connections around inside the motor - this is not a job for the faint hearted or unqualified.


    Or can all 3PH motors that support Star/Delta automatically work on 240V/Delta mode?
    Pretty much. Nearly all modern motors are made this way so that they can be exported to either Europe/China/OZ which uses 380 - 415V 3P OR US/Canada/ Japan, which uses 220V 3P.

    My cousin owns and runs an electric motor factory in Northern Italy. He hardly makes any single phase motors. He mostly makes 3P motor with a built in basic VFD and exports them all over the place. They are not cheap but they are highly versatile.

  9. #38
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    Quote Originally Posted by BobL View Post
    The name plate is a good but imperfect guide
    - some nameplates claim conversion is possible but when the junction is opened the required bits are missing and VV.
    Most old 415V 3P Y connected motors can be converted to 240V by taking them to a motor rewinder who will swap a few connections around inside the motor - this is not a job for the faint hearted or unqualified.



    Pretty much. Nearly all modern motors are made this way so that they can be exported to either Europe/China/OZ which uses 380 - 415V 3P OR US/Canada/ Japan, which uses 220V 3P.

    My cousin owns and runs an electric motor factory in Northern Italy. He hardly makes any single phase motors. He mostly makes 3P motor with a built in basic VFD and exports them all over the place. They are not cheap but they are highly versatile.
    Okay that explains it as I made the mistake of buying some motors cheap ages back with the intention to hook them up to a VFD I had, but the motors could only run on 415V, not 240V just by changing the config.

    I ended up scrapping them to recover the copper to melt, so they weren't a total waste! ;-)

    I did end up getting a couple of dirt cheap SEW motors with gearboxes that do have 240V/415V and the relative current draw on the nameplate. But that's a project for another lifetime most likely!

    Cheers, Ian

  10. #39
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    I'm coming a bit late in this thread but I want to point out is that motors for VFD applications are generally designed for that application; what manufacturers do is manufacture motors with a higher level of winding insulation to handle to output of a VFD which can damage ordinary insulation. There are other possible problems such as overheating but the result is the same, early failure if the motor is not compatible.

  11. #40
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    Quote Originally Posted by Eleventy View Post
    I'm coming a bit late in this thread but I want to point out is that motors for VFD applications are generally designed for that application; what manufacturers do is manufacture motors with a higher level of winding insulation to handle to output of a VFD which can damage ordinary insulation. There are other possible problems such as overheating but the result is the same, early failure if the motor is not compatible.
    I've had 11 different motors on machines with VFDs in my shed for up to 9 years and yet to see a compatibility problem with these motors. The only time I saw a hint of this was at the mens shed on an ~80 years old motor that got slightly warmer than usual and did not like working above about 60Hz. Sometimes I wonder if it's a ploy to sell new motors.

    Perhaps this might apply more to motors operating under high constant loads like pumps and fans but motors made for these applications already usually have beefier insulation anyway.

    On machinery like lathes and sanders the load is rarely constantly at the highest motor output ie the motor only runs at full load for short bursts.
    If the motor has to be replaced because its already a 415V ∆ and you want to run it on 240V a simple way around these potential problem is to double later power output of the motor being used.

    The motor I am most concerned about in my shed on a VFD is the 4HP WEA motor on my dust extractor since it operates at close to full power most of the time. This dust extractor has been installed in an enclosure and arranged so all the air from the filters passes by the DC motor to improve the cooling. I also put some temperature sensors on the motor, enclosure and also monitor inside and outside temperature and here's a typical temp/time profile - motor temperature rises by ~7º in 30 minutes. The motor comes from a water pump so it's pretty beefy.

    Screen Shot 2019-06-17 at 3.29.27 pm.png

  12. #41
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    Quote Originally Posted by Eleventy View Post
    I'm coming a bit late in this thread but I want to point out is that motors for VFD applications are generally designed for that application; what manufacturers do is manufacture motors with a higher level of winding insulation to handle to output of a VFD which can damage ordinary insulation. There are other possible problems such as overheating but the result is the same, early failure if the motor is not compatible.
    Hello Eleventy and welcome to the Forum. Your name sounds very Hobbitish .

    Are you referring to the small VFDs we are discussing in this thread or the large 415V industrial VFDs that are used primarily for variable speed control? We have a number at work, probably in the 50KW region, and they are almost certainly specially adapted for this purpose as at low frequencies the cooling fans may be inadequate. In fact I know that Bob has made reference in the past that if an application is continually working at around 25Hz, for example, you may have to may aware of the potential to overheat as the enclosed fan is travelling at a correspondingly slow speed.

    However, most of the time we are looking at 40Hz to 60Hz and it may not be an issue. A lathe is one machine where lower speeds may be more frequently used, but again I think Bob has some experience of this with his lathes so maybe not a big issue.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  13. #42
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    Quote Originally Posted by BobL View Post
    . The motor comes from a water pump so it's pretty beefy.
    I scrapped a 5HP 3PH pump motor a few months back, LOT's of really thick copper to melt down in that beast! I think if they're designed as a pump, they are built for the harshest conditions possible generally, especially so if it's Aussie made and not a cheap import.

    cheers, Ian

  14. #43
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    Quote Originally Posted by aarggh View Post
    I scrapped a 5HP 3PH pump motor a few months back, LOT's of really thick copper to melt down in that beast! I think if they're designed as a pump, they are built for the harshest conditions possible generally, especially so if it's Aussie made and not a cheap import.

    cheers, Ian
    Lost of water pumps motors are made to operate outside so they are made super rugged even if they are often located under some sort of cover.

  15. #44
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    Quote Originally Posted by Bushmiller View Post
    However, most of the time we are looking at 40Hz to 60Hz and it may not be an issue. A lathe is one machine where lower speeds may be more frequently used, but again I think Bob has some experience of this with his lathes so maybe not a big issue.

    Regards
    Paul
    Even WW turning at low speed is not a problem as one rarely applies heavy loads for more than a few minutes at a time.

    The heaviest load my 1HP WW WW lathe experiences at lowest speeds is when making Bell Mouth Hoods (BMHs)
    When I form the BMHs I run the motor at around 12Hz to prevent the PVC from getting too hot in one spot.
    If I run it faster than this the higher speed self cools the PVC I am trying to heat UP - running slower makes it too easy to stall during the forming process and can create hot spots that lead to ruck.

    To start with the BHM former and piece of PVF from which the BMH is formed are free running for a couple of minutes while a hot air gun is applied till the former and PVC reaches around 95º, during this time the motor draws about 2A. Then while continually heating the tail stock is used to push the PVC onto the former in intermittent bursts of around 5 seconds spaced out by periods of 30s. If I apply the push force too quickly the motor current rises dramatically and I can stall the 1HP motor at this stage but apply it so it keeps up most of the speed. The forming process takes about 90s. During this time the motor temperature barely rises.

    IMG_1877.jpg

    My MW lathe came with a 1/2HP motor but I replaced it with a 1HP motor. It only draws more that 1/2 of its rated current when taking long deep cuts with carbide tooling - this is a high speed process.
    Speeds less than 30Hz are unusual on the MW lathe - usually I'm between 35 and 100 Hz.

  16. #45
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    Quote Originally Posted by Bushmiller View Post
    Hello Eleventy and welcome to the Forum. Your name sounds very Hobbitish .

    Are you referring to the small VFDs we are discussing in this thread or the large 415V industrial VFDs that are used primarily for variable speed control? We have a number at work, probably in the 50KW region, and they are almost certainly specially adapted for this purpose as at low frequencies the cooling fans may be inadequate. In fact I know that Bob has made reference in the past that if an application is continually working at around 25Hz, for example, you may have to may aware of the potential to overheat as the enclosed fan is travelling at a correspondingly slow speed.

    However, most of the time we are looking at 40Hz to 60Hz and it may not be an issue. A lathe is one machine where lower speeds may be more frequently used, but again I think Bob has some experience of this with his lathes so maybe not a big issue.

    Regards
    Paul
    Thank you.
    That name originated from something else but people started referring to me as Eleventy and I adopted it because I like to put 110% effort in what I do even though my old boss used to tell me that perfection is too expensive, to which I always replied that less than 100% can also be expensive when you need to redo the work.

    All VFDs operate the same way and none of them produce a clean sine wave which is what all motors are designed for. The output from a VFD is a series of pulses timed to replicate a sine wave and many things can go wrong if the motor and the vfd are not properly matched (e.g.: overheating, winding failures, torque issues); it is a specialised field which requires training and experience before you become proficient, which I don't pretend to be myself. I just know enough about it from working in an electrical profession all my life which includes using VSDs and VFDs with small LV motors all the way up to large HV motors in pumping or conveyor applications. I know enough about the risks to never assume anything and I rely on people who are trained in that field to guide me to make final decisions that won't come back and bite me in the backside.

    Here's a bit of reading material on the subject (there are lots of technical papers on the subject : The Basics of Variable-Frequency Drives | Electrical Construction & Maintenance (EC&M) Magazine

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