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  1. #1
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    Default Running a 10hp 3 phase motor?

    So it turns out that the old New Visby lathe that I bought a couple of weeks ago has a 10hp motor.. From the limited info available online I was under the impression that the machine maybe had a 1-2hp motor or perhaps 5hp at most.

    20190601_192612.jpg

    Now, like many others I don't have 3 phase installed at my place and so I figure that I will need to run the unit via an RPC or VFD.

    I have a couple of questions:

    1. Can I run this motor using a suitably sized VFD from my single phase supply or am I better off replacing the motor with a smaller one? I assume that the lathe has a 10hp motor for a reason..

    2. Am I correct in assuming that the output capacity of the VFD needs to exceed the rated power of the motor? ie: it's not recommended to run a 10hp motor with a VFD rated at 10hp (7.5kw)?

    3. Is there a better way to run this motor than what I have suggested above (short of installing a 3 phase supply)?

    Cheers

    Flo

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Flo View Post
    1. Can I run this motor using a suitably sized VFD from my single phase supply.I assume that the lathe has a 10hp motor for a reason.
    No, the largest single to three phase VFDs are around the 5HP mark.
    To run a >5HP you'd need to install a beefy RPC and run it direct as 3 phase - this is not going to be cheap.
    or am I better off replacing the motor with a smaller one?
    I doubt a 5HP motor is going to cut it. The lowest I would go would 7.5HP

    2. Am I correct in assuming that the output capacity of the VFD needs to exceed the rated power of the motor? ie: it's not recommended to run a 10hp motor with a VFD rated at 10hp (7.5kw)?
    No, the best power for a VFD is in fact the same power rating as the motor. If you use a more powerful VFD it needs to be programmed "BACK" to the power rating of the motor anyway so its basically a waste of money.

    An XHP motor can usually be safely run on a <XHP VFD. VFDs are very good at looking after themselves so the VFD will simply not start or stop working once the current it is being asked to supply is greater than its programmed limit.
    Of course this has limits, eg I wouldn't be using a 1HP VFD to run a 10HP motor but I have certainly run a 3HP motor using a 1HP VFD - for testing purposes only of course - no load.

    3. Is there a better way to run this motor than what I have suggested above (short of installing a 3 phase supply)?
    Not really, you are pretty well stuck with getting 3P for something that size.

  3. #3
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    Hi BobL,

    Thanks for the prompt reply. I'm just going to add this to the growing list of challenges that I need to overcome!

    Cheers

    Flo

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Flo View Post
    Hi BobL,

    Thanks for the prompt reply. I'm just going to add this to the growing list of challenges that I need to overcome!

    Cheers

    Flo
    Here is what I would do - assuming the motor is a "Y" and can be converted to "∆"
    See if you can borrow a 5HP SP VFD and an Ammeter
    Disconnect everything except the spindle and see what current spindle running only draws.
    Play with the gears and see what currents are drawn - should not change much or at all.
    Add the various drives and monitor current.
    If it draws too much the VFD will just shut down.
    Whatever spare horses you have up to 5HP will be your working capacity.
    SO ,I doubt you't be taken 5mm cuts with it but yo might be able to use it.

  5. #5
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    Quote Originally Posted by BobL View Post
    Here is what I would do - assuming the motor is a "Y" and can be converted to "∆"
    See if you can borrow a 5HP SP VFD and an Ammeter
    Disconnect everything except the spindle and see what current spindle running only draws.
    Play with the gears and see what currents are drawn - should not change much or at all.
    Add the various drives and monitor current.
    If it draws too much the VFD will just shut down.
    Whatever spare horses you have up to 5HP will be your working capacity.
    SO ,I doubt you't be taken 5mm cuts with it but yo might be able to use it.

    The motor is in a delta configuration by default and the data plate says that it draws 13.2A which I'm guessing is its continuous no-load current draw?

    This is a project lathe so I'm not in any huge rush to get it running by tomorrow.. I'll try your suggestions and see what I come up with.

    Cheers

    Flo

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Flo View Post
    The motor is in a delta configuration by default . . .
    OK then you cannot use that motor with a single phase VFD as it's already a 415V ∆ motor.
    A 415V 3P Y can be converted to 240V by making it a delta, but if its a 415V ∆ then it will only run on something less than 1/2 power when connected to 240V.
    If you convert that motor to a Y it will become a 690V motor.

    To get anywhere

    and the data plate says that it draws 13.2A which I'm guessing is its continuous no-load current draw?
    No that will be a fully loaedd rating
    415 x 13.2 X 1.73 = 9kW
    9kW times a power factor say 0.8 = 7.6 kW or ~10.2HP

    You will have to swap the motor to run this on an SP-3P V FD.

  7. #7
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    Flo
    Have you posted pics of your lathe on the forum somewhere? How big is it.
    As its a New Visby its probably from around the 1940's. I used to have a "Visby" which had a flat bed and flat belt drive so I assumed it was possibly 1920-30's (guestimate). Anyway what I'm leading up to is how sure are you that the motor you have is the original? On a machine that old, that's had who knows how many owners, there's a good chance the motor you have is not original. I think the old Visby I had, had an old 2HP single phase on it when my father got it back in about 1980. It used to run it ok. So yours could well have had a smaller motor on it originally but that had been replaced with a bigger one. Maybe they wanted more power or maybe its as simple as they had that one available.
    If you can get away with a smaller motor its going to be a lot cheaper and easier for you to get it running again
    Just a few thoughts.
    Peter

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by bollie7 View Post
    FloHave you posted pics of your lathe on the forum somewhere? How big is it.As its a New Visby its probably from around the 1940's. I used to have a "Visby" which had a flat bed and flat belt drive so I assumed it was possibly 1920-30's (guestimate). Anyway what I'm leading up to is how sure are you that the motor you have is the original? On a machine that old, that's had who knows how many owners, there's a good chance the motor you have is not original. I think the old Visby I had, had an old 2HP single phase on it when my father got it back in about 1980. It used to run it ok. So yours could well have had a smaller motor on it originally but that had been replaced with a bigger one. Maybe they wanted more power or maybe its as simple as they had that one available.If you can get away with a smaller motor its going to be a lot cheaper and easier for you to get it running againJust a few thoughts.Peter
    Good point.
    How big are the chucks and what is the swing as these are good indicators of power requirements.

  9. #9
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    I think it's about a 14" swing machine, my previous macson was 16" with 14" Chuck's and was 5hp from the factory. My current 14" DSG is 5.5hp. Both could move about as much metal as I would ever want to, at least 1/4 radial depth of cut at heavy feeds I'd say that 10hp motor was grafted on after the fact.

    Modern lathes of the same size would have around 7 - 10 HP these days but no way in the 50s were you getting that kind of juice unless by special order.

  10. #10
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    Quote Originally Posted by bollie7 View Post
    Flo
    Have you posted pics of your lathe on the forum somewhere? How big is it.
    As its a New Visby its probably from around the 1940's. I used to have a "Visby" which had a flat bed and flat belt drive so I assumed it was possibly 1920-30's (guestimate). Anyway what I'm leading up to is how sure are you that the motor you have is the original? On a machine that old, that's had who knows how many owners, there's a good chance the motor you have is not original. I think the old Visby I had, had an old 2HP single phase on it when my father got it back in about 1980. It used to run it ok. So yours could well have had a smaller motor on it originally but that had been replaced with a bigger one. Maybe they wanted more power or maybe its as simple as they had that one available.
    If you can get away with a smaller motor its going to be a lot cheaper and easier for you to get it running again
    Just a few thoughts.
    Peter
    Hi Peter,

    Yes I have in the metal work general section, but just a quick indicator the machine is about 2.5m long, about 1.3m high.. the bed is about 1.4m long.. and the thing weighs almost 2 tonnes..

    The motor looks right for the period but is a different colour to the rest of the machine. This could mean that it is not original or that the machine has been repainted at some point but the motor was left as is. Looking closely at it there is some permanent marker written on it which could support the non OEM motor scenario..

    20190604_215128R.jpgIMG_2742.jpg 20190601_192612.jpg

    Quote Originally Posted by BobL View Post
    Good point.
    How big are the chucks and what is the swing as these are good indicators of power requirements.
    The 3 jaw chuck that is currently fitted is over 300mm diameter.. The lathe is classified as 8.5" which I assume is the centre height. The lathe has a gap in the bed and with a faceplate installed you could turn a piece over 600mm in diameter.

    20190604_215400R.jpg

  11. #11
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    Quote Originally Posted by caskwarrior View Post
    I think it's about a 14" swing machine, my previous macson was 16" with 14" Chuck's and was 5hp from the factory. My current 14" DSG is 5.5hp. Both could move about as much metal as I would ever want to, at least 1/4 radial depth of cut at heavy feeds I'd say that 10hp motor was grafted on after the fact.

    The motor "looks" original but as per my previous post there's a few things which don't add up.. it's different colour to the rest of the machine for a start, it has permanent marker on it (which may or may not mean anything) and the data plate has been modified..

    Modern lathes of the same size would have around 7 - 10 HP these days but no way in the 50s were you getting that kind of juice unless by special order.
    That makes sense as all the thing I have read about these lathes mentioned either 1-2hp motors for the earlier Visby's or 5hp for the "Record" and "Conemaster" lathes.. no mention of a 10hp motor..

  12. #12
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by caskwarrior View Post
    I think it's about a 14" swing machine, my previous macson was 16" with 14" Chuck's and was 5hp from the factory. My current 14" DSG is 5.5hp. Both could move about as much metal as I would ever want to, at least 1/4 radial depth of cut at heavy feeds I'd say that 10hp motor was grafted on after the fact. .
    I agree it looks like a 5HP motor would be OK on that lathe.

    Just so you are aware you can't really run a a 5HP VFD from a 10A or even really a 15A GPO - you will need a 20A GPO on its own line and its own (25A?) breaker. You need to check with a sparky about this.

  13. #13
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    Quote Originally Posted by BobL View Post
    I agree it looks like a 5HP motor would be OK on that lathe.

    Just so you are aware you can't really run a a 5HP VFD from a 10A or even really a 15A GPO - you will need a 20A GPO on its own line and its own (25A?) breaker. You need to check with a sparky about this.
    Ok great. Thanks for that.. I was starting to think RPC's or just biting the bullet and getting 3 phase power installed! At least a what you have suggested gives me a goal..

  14. #14
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    Quote Originally Posted by BobL View Post
    I agree it looks like a 5HP motor would be OK on that lathe.

    Just so you are aware you can't really run a a 5HP VFD from a 10A or even really a 15A GPO - you will need a 20A GPO on its own line and its own (25A?) breaker. You need to check with a sparky about this.
    Another question: does the replacement motor need to be the same spec in terms of rpm, number of poles and voltage? ie: is it better to run at 415v than 240v 3 phase? I'm not sure what rpm the current motor operates at as there are two speeds stamped on the data plate - the higher of the two is 1445 rpm so I guess a 1400 rpm would suffice rather than 2800 rpm?

  15. #15
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Flo View Post
    Another question: does the replacement motor need to be the same spec in terms of rpm, number of poles and voltage? ie: is it better to run at 415v than 240v 3 phase?
    RPMs and #poles - YES, there's no difference with the Voltage.

    If you buy/acquire a new or near new 5HP motor then make sure you get one that will run both on 415 3P (Y) and 240V 3P (∆).
    These are almost standard these days and the conversion is a doddle and done in the motor mains connection box by switching a couple of connectors around.

    I'm not sure what rpm the current motor operates at as there are two speeds stamped on the data plate - the higher of the two is 1445 rpm so I guess a 1400 rpm would suffice rather than 2800 rpm?
    1440 would be fine.

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