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Thread: Old motor & VFD

  1. #1
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    Default Old motor & VFD

    It says induction motor on the plate and delta. Is there any reason a Vfd can't be connected to this motor without modification?
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    BobL is offline Member: Blue and white apron brigade
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    Is it a 440V ∆ motor? - if it is and you connect it to a 240V 3P VFD you will only get half the power.
    It will need to be connected to a 440V VFD to get full power

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    415v 3ph and I want to use a 240 single - 3oh vfd.

    Motor is a 3hp integrated into the machine.
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    …..Live a Quiet Life & Work with your Hands

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    BobL is offline Member: Blue and white apron brigade
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    I have tried VFDs out on several old motors that looked very similar to that motor and they ran at half power and did not like going over 60Hz.

    They would have to be rewound to run at full power on 240V 3P.

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    I agree with BobL.
    There is one other way: you can find a transformer to change the single phase 240V into 415V single phase (at say 3kW) and get a 380-440V single to 3-phase VFD. That might be more cost-effective than rewinding....
    Cheers, Joe
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    I'm in the process of converting all my gear over to 240v and most of the small gear is underway. Just waiting on a few used VFD I got off ebay to arrive. The quotes for getting 3phase connected are so high.

    This big bandsaw looks like it may be an issue. I also have the 12" jointer and the Colchester master2500 both with large motors.

    BOBL any idea what it costs to have a motor like this rewound? And what does that mean? Will it be rewound for 240V or rewound so it will accept the VFD with full power?

    Joe, How & where do I find such a transformer? In this scenario I assume a 380-440V single phase IN to 3-phase 380-440V OUT VFD will be more rare and expensive than the one usually found on ebay??
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    The other thing I have thought about whilst not as expensive or convenient as connecting 3 phase is a hideously expensive rotary phase converter or similar power box.

    Is there any limitations as to what types of 3 Phase motors that can be plugged in to one? i.e would the motor above work with one?
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    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by DSEL74 View Post
    BOBL any idea what it costs to have a motor like this rewound? And what does that mean? Will it be rewound for 240V or rewound so it will accept the VFD with full power?
    Sorry can't help with this as the last time I had a motor rewound was more than 3 decades ago.
    My guess is several hundred.
    A rewinder should be able to rewind it for 240V 3P although there may be some reluctance to do it since it's not how the motor is originally wound.
    It's still worth asking though. I would look for a rewinder that has been around for a while and is prepared to consider it as a restoration

    A rotary phase converter would work fine and you could also use it with any other 415 - 440V 3P delta powered machinery you might happen to acquire.

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    380/415V VFDs are just as available as 240V VFDs - from the same makers and usually at similar prices.
    2 2KW 3HP VFD 3PHASE 380 415V 5 1A Variable Frequency Drive Inverter ISO | eBay or 2 2KW 380V 3HP 5A Mini Size Variable Frequency Drive Inverter VFD Good Quanlity | eBay
    The transformers I mention are used quite a bit, usually in the opposite 'direction': 415V in and 240V out - but they work equally well stepping up. Maybe look ofr 'step dopwn' transformer. I have a couple here, but only 1kW....
    There are also autotransformers around 415V in and taps for 220 and 240V. I expect they would work too. Someone else here may be able to advise. Be aware that they don't isolate. Which means that you can get a nasty 415V shock in relation to ground if you touch the live end!
    Bob's suggestion that rewinders might be reluctant to rewind your motor is because they have to CALCULATE the new winding. It will have less turns but thicker wire. The problem is that there will be physical limitations as to how many and how thick a winding they can fit into the space (because fatter wires take more space, leaving bigger empty spaces). So it takes someone experienced to do that quickly. If the person isn't used to electrical engineering calculations in this context, then they might just say "it can't be done".... or quote so that you give up. These skills are fast disappearing, sadly. Give RayG a call, his SIL is in the trade and he doesn't give up because something is hard - quite the opposite.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

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    A good source of 240/415 transformers is old multi voltage stick welders.

    I picked up an 11KVA multi voltage welder for around $50 which I was going to use for my RPC, but subsequently found a brand new/never used 20KVA transformer instead (for $100 delivered).
    Cheers.

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    So it takes someone experienced to do that quickly. If the person isn't used to electrical engineering calculations in this context, then they might just say "it can't be done".... or quote so that you give up. These skills are fast disappearing, sadly. Give RayG a call, his SIL is in the trade and he doesn't give up because something is hard - quite the opposite.
    Yep we are into the "just change it over age". In the defence of them tho, time is a killer and I know from experience if you are hiring folk
    to do a job, their time (and the cost of) adds up fast.

    Good luck with your project, interesting to see the final result.
    Frisky wife, happy life. ​Then I woke up. Oh well it was fun while it lasted.
    From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".

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    Quote Originally Posted by Vernonv View Post
    A good source of 240/415 transformers is old multi voltage stick welders.

    I picked up an 11KVA multi voltage welder for around $50 which I was going to use for my RPC, but subsequently found a brand new/never used 20KVA transformer instead (for $100 delivered).
    What's s multi voltage welder


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    Dale,
    did you get any further with the VFD for the 12 pole delta 415 motor? You didn't mention it when I was there. The easiest solution is probably to get a VFD from Arc Euro that has 240V single phase in and 415V 3-phase out, just not cheap....

    Arron,
    there are arc welders made to run on 240, 480 or 415 V. They are often single phase for home, farm and industry use. If you connect 240 to them, the 415V terminal in them will have 415V you can use. They would be working as an 'auto-transformer' and will not be isolating the load from the grid.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

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    Quote Originally Posted by jhovel View Post
    Dale,
    did you get any further with the VFD for the 12 pole delta 415 motor? You didn't mention it when I was there. The easiest solution is probably to get a VFD from Arc Euro that has 240V single phase in and 415V 3-phase out, just not cheap....

    Arron,
    there are arc welders made to run on 240, 480 or 415 V. They are often single phase for home, farm and industry use. If you connect 240 to them, the 415V terminal in them will have 415V you can use. They would be working as an 'auto-transformer' and will not be isolating the load from the grid.
    Thanks joe I've not herd of them.



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