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  1. #1
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    Default 440 volt Motor suitability for use with 220 volt VFD

    I have successfully converted a few motors from Star to Delta for use with single phase input VFD's but this one may not be so easy. Does anyone have any experience with a Delta connected motor. I would like to keep the original motor because it has a unique type of flange mount.


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  2. #2
    BobL is offline Member: Blue and white apron brigade
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    It's not possible to convert this motor, you'll have to replace the motor or get it rewound.

    Most of the conversions I have undertaken have been single to 3 phase so involve complete motor replacement and about 1/3rd of these have involved flange modifications. If you are a metal worker it is often cheaper to go this route than getting the motor rewound.

  3. #3
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    Hi Techo1, Guys,

    I would take a very careful look inside ! You might find that you can remove the stator fairly easily, in which case you will be able to get a good look at where all the internal connections are. I've fitted new ball races to a similar looking Brooks motor on a wood work moulder. In any case a re-winder would have to get at the stator to rewind it.

    Those stators are usually just pressed in, there may be a step at one end and sometimes they put a pin in through the side that may have to be drilled out.
    Best Regards:
    Baron J.

  4. #4
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    Thanks for your input Baron and Bob. The reason that I decided to ask the question here is that while searching the internet yesterday I came across some information that suggested that it could be done, although it seems counterintuitive to me, what do you guys think?

    Star/Delta motor connection 380V/220V | GoHz.com

  5. #5
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    Hi there, I have converted several motors from star to delta in order to run off 240V 3PH with a VFD. I don't understand the benefits of converting a delta motor to star. Unless of course it was converted to run off a VFD and you want to convert back to the original condition and run off 380 or 440V 3PH.

    Edit: I just read the link above. I'm confused about what you want to achieve. So you currently have a stock standard 3PH machine that has a delta wired motor and you want to run it on a VFD?

    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.

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    A 240V 3P Motor can run from a VFD in either ∆ or Y mode, BUT it has to be set up for not just "∆ or Y but "240V ∆" or "240V Y".

    It just so happens that if a 440-415V Y is converted to ∆ becomes a 240V ∆ and VV
    However, if a 440-415V ∆ is converted to Y it becomes a 690V Y and VV

    You can of course run a 440V Y or ∆ from 240V 3P without any conversion and it will deliver somewhat less that half its rated power.
    This seems to work better on some motors and not so well on others.

    The only way to get full power is to have it rewired.

  7. #7
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    The way I look at it, with star wired motors the current path goes though 2 field windings through the motor as opposed to delta where it only sees one winding.

    In a simplistic view this means that star wired motors need twice the voltage to get the same current running though the windings.

    This is why delta wound motors can get full power when changed from star and run on 240V 3ph. It's half the voltage driving the current but it's also half the resistance, or impedance.

    Simon

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  8. #8
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    Quote Originally Posted by simonl View Post
    Hi there, I have converted several motors from star to delta in order to run off 240V 3PH with a VFD. I don't understand the benefits of converting a delta motor to star. Unless of course it was converted to run off a VFD and you want to convert back to the original condition and run off 380 or 440V 3PH.

    Edit: I just read the link above. I'm confused about what you want to achieve. So you currently have a stock standard 3PH machine that has a delta wired motor and you want to run it on a VFD?

    Simon

    Correct, a 220/240 volt output VFD.

  9. #9
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    Quote Originally Posted by Techo1 View Post
    Correct, a 220/240 volt output VFD.
    OK. Like others have said, it will run the way it is right now but it will be down on power. Converting it to star will make it even lower in power if you ran it on 240V. It certainly won't help I wouldn't have thought.

    Leave it the way it is and see if the power output is acceptable for your needs. My mill has a 3 HP motor but I doubt whether I will ever ask full power out of it for my home use needs. I'm sure if I had a 2 HP motor it would still do what I need.

    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.

  10. #10
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by simonl View Post
    OK. Like others have said, it will run the way it is right now but it will be down on power. Converting it to star will make it even lower in power if you ran it on 240V. It certainly won't help I wouldn't have thought.

    Leave it the way it is and see if the power output is acceptable for your needs. My mill has a 3 HP motor but I doubt whether I will ever ask full power out of it for my home use needs. I'm sure if I had a 2 HP motor it would still do what I need.

    Simon
    I have a small WW lathe that came stock with a SP 240V 1/2HP motor.
    I ran a 1HP 415V Y motor using a 240V VFD for about 3 years without any probs before I converted it to ∆.
    At 50Hz it had about the same HP as the original 1/2HP motor.

  11. #11
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    Hi Guys,

    There are plenty of Brooks motors about ! Removing the stator and having it rewound is one solution, another would be to transplant a stator from a single phase Brooks motor with the same stator size.

    Brooks made a lot of variations of motors using the same size lamination stampings. I do know that the stack up varied in hight between motors using the same size laminations and having different power ratings. The other thing that varied was the rotor shaft sizes. A lot of variants used the same size bearings but the output shaft diameters varied. You shouldn't need to change the rotor.

    Note that different motor manufacturers may not use the same size stator for their motors, so if you thought about doing a transplant you need a Brooks motor. One other thing the wires on the transplant may not be in the same place so you will have to make sure that the stator is the right way round or the motor might run backwards. Unlike 3 phase you wont have a pair of wires to swap round to reverse direction.

    HTH.
    Best Regards:
    Baron J.

  12. #12
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    Thanks again for all information. So am I correct in assuming that the information in the link to the GoHz.com site is incorrect or are they just not telling the whole story, regarding the 50% loss of power, which I suspected in the first place?

  13. #13
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Techo1 View Post
    Thanks again for all information. So am I correct in assuming that the information in the link to the GoHz.com site is incorrect or are they just not telling the whole story, regarding the 50% loss of power, which I suspected in the first place?
    Describing VFDs and their V connection requirements is tricky and that site looks like it has made a bit of a dogs breakfast with it but there's nothing actually incorrect in what they said.
    They just failed to mentioned the loss in power of the systems we are discussing.
    Regarding connecting up any V to any motor wiring connection, they do actually say,
    The efficiency and power factor will NOT be as per design and you must understand this. Setting up the protection is tricky and safety first, please.

  14. #14
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    Quote Originally Posted by Techo1 View Post
    I would like to keep the original motor because it has a unique type of flange mount.
    How badly? $1382* badly? https://www.ebay.co.uk/itm/152176133868

    Not cheap but I've heard some pretty large numbers for rewinding motors lately. At least with rewinding you get to use a cheap 240V VSD. So I'd start by pricing a rewind and go from there.




    *Minus 20% VAT if you can get the seller to do it, plus 10% GST.

  15. #15
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    Quote Originally Posted by Stustoys View Post
    How badly? $1382* badly? https://www.ebay.co.uk/itm/152176133868

    Not cheap but I've heard some pretty large numbers for rewinding motors lately. At least with rewinding you get to use a cheap 240V VSD. So I'd start by pricing a rewind and go from there.

    *Minus 20% VAT if you can get the seller to do it, plus 10% GST.
    Hi Guys,

    That could be the cheapest way to go ! The VAT doesn't apply to overseas sales, but do make sure that the seller knocks the VAT off. A lot of sellers don't or inflate the price to cover overseas sales. The postage is a rip off, the UK post charges for overseas is extortionate.

    The seller is about 80 or so miles south of me so I could have a word if you wanted me to.
    Best Regards:
    Baron J.

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