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  1. #1
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    Question What / Where to buy a decent VFD

    Hey people,

    Have bought a 3-phase lathe but only have single phase power, started research into VFD's, But no idea what I need exactly or where to buy one, There is a few on ebay but electronics sure isnt cheap China's strong suit so abit wary.

    Current lathe only has a 2HP motor but may upgrade the motor in future or want to use the VFD on future machines. Does the VFD need to be exactly matched to the motor? or can you use say a 4hp VFD on a 2HP motor with no problems?

    Whats the largest HP VFD you can run on single phase 15amp power, Im guessing 3hp since thats about the largest single phase motor you can run?

    So yea just wondering on tips on what to look for in a VFD and if anyone can recommend a good supplier?

    Thanks

  2. #2
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    So after abit of research it seems if you go over 3hp (why is this the magic number?) you need to double the size of the VFD, ie if you want to run a 5HP motor you need a 10HP VFD? but also needs 30amp supply, so Im guessing id new a new electrical circuit fitted to the workshop... can you even get a 30amp single phase circuit?

    Also abit confused about the hz... My current motor's plate says 50hz, but VFD's ive seen run up to 400hz... does this mean I can only use 0-50hz range? how much "overdrive" can a motor usually handle?

    Lastly should I even be going down this route? or should I just get a 3HP single phase motor, I do like the idea of the variable speed of the VFD tho especially since my lathe is Belt drive and doesnt have a quick change gearbox... altho it is pretty quick to move the belt. But on that note I have a mini lathe which has a single phase 500w brushless motor and a pot on the control panel which lets me vary the speed of the motor... can this be done on only single phase motor or only brushless?

  3. #3
    Join Date
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    plenty of others on this forum who know more about VFDs than I, but will outline some of the basics.

    first Id be checking out how your existing 2hp lathe motor is wired - either Y (star) or delta. if its already factory delta wired then I dont think these can generally have a VFD connected or be easily reconfigured. To connect a Star wired 3phase motor you need to do some minor re wiring inside the case to put it into delta mode. If its a more modern 3phase motor then you may be able to change some connectors in the connection box to get it into delta mode.

    VFDs are fine to be rated at a higher power than your motor - you just need to program the VFD for the correct Amperage rating for your motor (on 3phase 240v). As for the Hz. 240 v or 415v supplied at the plug is supplied at 50 hz. However the VFD will output a Variable or programable frequency that drives the motor. for example the VFD could output 50hz which will run your 2hp motor at its 'normal' rated speed. If you increased the vfd output frequency (Hz) to 100hz you would be running the motor at twice its normal speed. Most 4 pole motors will easily handle double speed and a bit more but not sure you would want to run one at 400hz for long.

    hope thats clear enough as the whole VFD thing can be a bit of a learning curve if you are starting out. Suggest you should do some more reading and ask a few more questions. there should be some threads on this forum about doing the conversion also.

    cheers

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Viperx85 View Post
    So after abit of research it seems if you go over 3hp (why is this the magic number?) you need to double the size of the VFD, ie if you want to run a 5HP motor you need a 10HP VFD?
    This is not correct.

    whoever said that may be getting confused with the fact that most older VFDs and motors will only allow a motor to develop max power that is proportional to the frequency up to its rated frequency.
    Lets say a motor is rated at 2HP at 50Hz, At 25Hz it will only produce 1HP and at 12.5Hz it will only produce 1/2HP.
    Above 50Hz it will be able to produce 2HP up o about 100Hz and then after that it will reduce and be virtually useless at around 200Hz (if it hasn't fallen apart by then anyway) ie danger Will Robinson.

    Zsteves comment about the existing motor being already wired as a ∆ is important - this means the motor will need to be swapped out for a suitable motor. This in turns leads to a need for motor/shaft pulley compatibility requirements, motor bracket compatibility etc - it can be a lot more trouble than you think.

    Also abit confused about the hz... My current motor's plate says 50hz, but VFD's ive seen run up to 400hz... does this mean I can only use 0-50hz range? how much "overdrive" can a motor usually handle?
    it depends on the motor, characteristics (old motor don't like being drive too fast because they have poor magnetic characteristics), bearings and whether its a 2 or 4 pole motor. Most 4 pole motors machines (except grinders) will run to about 120Hz some may go to 150Hz OK. Grinders are usually limited by the wheels. 2 Pole motors are limited by bearings so 90Hz is about tops. Old large chucks on lathes cannot be spun too fast either.

    Lastly should I even be going down this route?
    This is a how long is a piece of string question - before you go any further read this thread in the woodies forum
    VFD install summaries

    I suggest you read that thread all the way through, especially Posts 4 and 7 which will highlight the problems an pitfalls. Only if you are comfortable working with Mains V should you be going anywhere need a self installation of a VFD. If not the costs can escalate drastically and you pretty quickly you'll find it cheaper to go with a single phase motor.

  5. #5
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    One thing Bob didn't mention is that the VFD can be programmed for a slower ramp up to speed so you don't get the big amperage spike you get with a single phase motor when it starts. That would keep from tripping your 15 amp breaker but still allowing a bigger motor. Your 2hp motor would be fine with the existing circuit I believe.

    Pete

  6. #6
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    Quote Originally Posted by Viperx85 View Post
    can you even get a 30amp single phase circuit?

    sure can...need to be protected with suitable circuit breaker and if you need a plug use a single Ph industrial outlet.

    you can even get 20amp 3 flat pin general purpose outlets and male plug to suit along with female socket if you need to make ext cord

  7. #7
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    All good, but, where do you get them, ebay I'm guessing??? Write VFD in and all sorts of things come up! Oh and are the ones from China any good?

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by onanonanon View Post
    All good, but, where do you get them, ebay I'm guessing??? Write VFD in and all sorts of things come up! Oh and are the ones from China any good?
    Yep ebay is a start. If you want to buy inside Aus (their gear is all imported from China) and get local support and a 2 year warranty try https://cononmotor.com.au/product-ca...equency-drive/

    Some tips

    Don't buy one you cannot preread and understand the manual before you buy - Manuals range from 200+ pages of real English to a couple of pages of garbage. The woody forums are full of posts of members purchasing VFDs with two page manuals that no one understands and then expecting members to solve their installation problems.

    It's far better to get one that either has a really good manual you can understand, or makes/models that forum members are already familiar with. Its no use buying something that no one knows about and expect them to read and understand the manual for you.

    Probably the most popular with forum members are the Huanyang or HY VFD. A few members know about Powtran VFDs - if you search the MW forums for POWTRAN VFDs there are several threads that show you how to purchase direct from the Powtran Factory - its a bit more complicated than buying from ebay but their VFDs are worth it.

  9. #9
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    So abit more research and wiring them up seems quite straight forward as well as setting up parameters like ramp up/down, min/max hz, current limiting etc.

    Was having a look at the conon motor 3HP one
    https://cononmotor.com.au/product/2-...ter-vsd-vfd-2/

    It States Input current is 23amp? Is this the max current draw? curious why input is so high for only 3hp? where a 3HP single phase motor will draw 13-15amps?

    Output is 10amp so im guessing this means it can support a 10amp FLA motor.

    I want to run the machine off my current 15amp power outlet so it seems the largest VFD I can go is the 2HP one that states 14amp input current?
    https://cononmotor.com.au/product/1-5kw2hp-7a-240v-ac-single-phase-variable-frequency-drive-inverter-vsd-vfd-2/

    Next question is it states output voltage on both of them is 3 Phase 240V but we use 415V 3phase in Aus??

    Next is the motor, I read somewhere that sometimes you need to do a mod on the motor and wire it as a Star or Delta config, can any 3-phase motor be wired to suit or Do i need to make sure I get the correct motor? is it just a matter of how you connect the power cables to the motor?

    Was looking at this 2HP motor on ebay, its 4-pole so 1400rpm which is closer to the 1100rpm of the original motor and from what ive read 4-pole has more torque compared to a higher rpm 2-pole motor?

    Is this a suitible motor to match with the Conon 2HP VFD It doesnt show a pic of the motor plate and doesnt say what amp it draws
    https://www.ebay.com.au/itm/3-PH-Thr...sid=m570.l1313

    Thanks Guys!

  10. #10
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    It has been discussed here...keep in mind that you might have to pay 10% on top if buying from oversea via ebay now.
    //metalworkforums.com/f309/t201140-powtran-vfds

  11. #11
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Viperx85 View Post
    So abit more research and wiring them up seems quite straight forward as well as setting up parameters like ramp up/down, min/max hz, current limiting etc.
    Was having a look at the conon motor 3HP one
    https://cononmotor.com.au/product/2-...ter-vsd-vfd-2/
    It States Input current is 23amp? Is this the max current draw?
    This is max current draw for a short period of time (~150s)

    curious why input is so high for only 3hp? where a 3HP single phase motor will draw 13-15amps?
    3HP SP motor typically use 10A. But don't forget the current is load dependent. I have ammeters on most of my gear and my 3HP Table saw draws anywhere between 6 and 15A.

    Output is 10amp so im guessing this means it can support a 10amp FLA motor.
    Yes a 3HP motor.

    Next question is it states output voltage on both of them is 3 Phase 240V but we use 415V 3phase in Aus??
    415v 3Phase is the Aus mains 3P supply but most new 3P motors can run on both 240 and 415V with a small connection modification. This is so they can operate in both Europe and North America.

    Next is the motor, I read somewhere that sometimes you need to do a mod on the motor and wire it as a Star or Delta config, can any 3-phase motor be wired to suit or Do i need to make sure I get the correct motor? is it just a matter of how you connect the power cables to the motor?
    You need the correct motor.
    A 415V 3P motor wired in delta (∆) cannot be converted.

    A 415V 3P motor wired in Star (Y) connection can usually be converted to 240V ∆. Sometimes this can be done at the motor mains connection box, if not the motor has to be opened up and modified internally - usually the is best left to a motor rewinder.

    If you ever find a 240V 3P ∆ wired motor that will also work fine.

    I understand all the Conon 3P motors are convertible in the mains connection box.

  12. #12
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    Ok so to run with a VFD it must be 240V Delta correct?

    When you convert a 415v 3P Star to 240v 3P Delta does it de-rate the motor, as in do you loose horsepower/torque?

    I noticed on the ConanMotor website it states
    Please note, This product is designed for the Australian market, which is 240V, unlike some VFDs in the market which is 220V.
    Most other around are 220V but with +/- 10% is this any problem at all to use in Aus?


    This is max current draw for a short period of time (~150s)
    Does this mean I could get away with using the 3HP VFD and run fine on my 15amp circuit but might trip if the machine really bogs down?

  13. #13
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Viperx85 View Post
    Ok so to run with a VFD it must be 240V Delta correct?
    It MUST be 240V 3P, but doesn't matter if it's Y or ∆, but the only place you are ever likely to see a 240V ∆ 3P motor is in North America.

    When you convert a 415v 3P Star to 240v 3P Delta does it de-rate the motor, as in do you loose horsepower/torque?
    No - same power/torque.

    I noticed on the ConanMotor website it states
    Most other around are 220V but with +/- 10% is this any problem at all to use in Aus?
    Not really - its just advertising blurb to me. If you buy a decent VFD the electronic components should be able to cope with 250V.

    Does this mean I could get away with using the 3HP VFD and run fine on my 15amp circuit but might trip if the machine really bogs down?
    One of the main reasons for running 3HP motors on 15A circuits is because of high start up currents.
    However, by programming the VFD to start the motor slowly ie over 5s or so, the start up currents won't usually go over 10A so you can run a 3HP VFD and motor from a 10A GPO.
    The VFD should be programmed not to go over say 12A for more than a minute or so which the breakers on a 10A circuit can usually handle.

    If installed correctly VFDs are very good at protecting themselves and motors.

    BTW in case you are not aware it's considered polite netiquette to thank people who provide lots of detailed information.
    There are buttons under each post for that. A member that posts lots of questions and thanks nobody may have their questions and posts ignored.

  14. #14
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    I do appreciate your posts Bob, very helpful! Still reading through the 13 page post on the woodwork forums where you have supplied a heap of info.

    I contacted Nicole from Powtran via the email address you supplied, replied with:
    PI160 2R2G1Z *1PC: USD87
    RESISTOR 300W/70R*1PC: USD8
    FREIGHT : USD28
    TOTAL: USD123
    So I think ill be going that route

  15. #15
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    nuttall motor wiring.jpg

    So I pulled the cover off the existing motor, Am I correct in saying that you cannot tell weather its Star Or Delta just from looking at that as you can only see 3 wires and the Star or Delta connection would be somewhere within the motor and would re-quire disassembly to find out?

    Thanks in advance

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