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  1. #31
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    Thanks Bob, good tip.

  2. #32
    BobL is offline Member: Blue and white apron brigade
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    I noticed your VFD has no capacity for cable glands - if you are not going to install it inside an enclosure this is what I usually do.
    CheapVFD.jpg

    That way if someone accidentally yanks on one of the cables they won't pull off the VFD terminals.
    The alternatives is to make sure they are tucked well out of the way of this possibility.

    Sorry to be a PITA but something else I spotted in your photo was the motor was just a touch too close to the edge of the bench for my liking. Sometimes if the motor is not wired correctly it can still sort of still work (but not for long ) and they can also bunny hop around on (and off) the top of the bench.

  3. #33
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    Not a PITA Bob. Thanks again. I have three VFDs now and none of them are mounted as yet. "one of those things" I must get around to doing - but I haven't really thought of anything I like in terms of mounting them - and each usage is different . I like your system there. Nice and simple.

  4. #34
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by StrayAlien View Post
    Not a PITA Bob. Thanks again. I have three VFDs now and none of them are mounted as yet. "one of those things" I must get around to doing - but I haven't really thought of anything I like in terms of mounting them - and each usage is different . I like your system there. Nice and simple.
    There's a few blokes I know that have their VFDS just laying loose on their machine bench alongside their machine. Like other issues not really a problem if hardly anyone comes into your shed. Given a few other things I have in my shed I also wouldn't say say I'm the safest operator but especially for newbies it's worth knowing potential problems etc

  5. #35
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    Quote Originally Posted by StrayAlien View Post
    I need to make a double pulley for the new shaft diameter, a mounting plate, and also figure how a VFD fits into wiring there and fwd/rev control box and so on. I'll have some questions about that no doubt.

    Greg.
    You cannot use the switch gear in the machine to directly switch the motor between the VFD and the motor, as any interruption in that circuit can blow the output devices in the VFD.

    However you may be able to use the existing switching to operate the low voltage remote controls for the VFD, depending on the physical condition of the individual switches if you wish to maintain the stock appearance of the lathe, or alternatively either make a new control panel to mount at the lathe with low voltage/low current switches, or if suitable, possibly mount the control panel from the VFD in a housing at the lathe and use it. The switches vould generally not need to handle more than 5V and 5mA. Using original switchgear could be an issue if it was configured to direct switch the motor, as the switch contacts may be pitted etc and not reliable at low voltage/low current after spending a lifetime directly stopping and starting a mains powered motor. If the original motor was controlled by contactors doing the hard work, the actual control switches would most likely have been switching around 24V at 100mA, so should be in reasonable condition to switch 5V/5mA for controlling the VFD. Switch contact size, spacing and materials are generally selected in accordance with the use they will receive, and a switch intended to direct switch a mains motor would not normally be a good choice for switching low power control signals.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  6. #36
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    To add to what Malb has posted, I recently put a VFD on my TOS mill, and used the original contactors to switch low voltage control side of the VFD.
    Worked really well, particularly as there's a lot of electrickery involved on the TOS with electric clutches and brakes for feed control etc and secondary circuits off the control switching for lube pumps etc.

    If you've got anything other than a simple on-off switch for the main motor then I highly recommend at least trying the contactor option for a start. It means all your other controls etc stay the same. If the contactor contacts are tired and not doing a good job of the LV switching then you've got to choose another option anyway, but its a quick and easy path to try.

    Steve

  7. #37
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    Hi there,

    I know I have come into this conversation a little late but with all my star to delta conversions (done about 5 now) once I find the star point, I always bring out all 6 connections to the junction box. I do this mainly for completeness and reversibility but also if I have somehow made a mistake with the delta connections, I can always fix it from within the junction box.

    If I was in the business of making 3ph electrical motors, I would generally always bring out all 6 connections to allow for versatility and ease of testing.

    Just my thoughts.
    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.

  8. #38
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by simonl View Post
    If I was in the business of making 3ph electrical motors, I would generally always bring out all 6 connections to allow for versatility and ease of testing
    That is pretty much standard now.
    My cousin in northern Italy owns a small electric motor factory (Up too 7.5kW). He does a lot of custom motor work and nearly all his motors are 3Phase or 3Phase with a very basic single phase VFD. Straight single phase motors are only supplied as a custom item.

    Here is a typical 3P motor with on boards VFD .

    Screen Shot 2020-06-19 at 3.03.19 pm.png

  9. #39
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    Hi Greg, Guys,

    Do not apply power to the motor windings without the rotor in there ! I understand why you did that, but the windings will get hot quite quickly. Bob already beat me about not using croc clips.
    Best Regards:
    Baron J.

  10. #40
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by BaronJ View Post
    Hi Greg, Guys,

    Do not apply power to the motor windings without the rotor in there ! I understand why you did that, but the windings will get hot quite quickly. Bob already beat me about not using croc clips.
    You can ??

    Anyway it looks like he did have the rotor in but it appears he had the fan cover off?
    I've seen a mains cable attacked by a fan - fortunately it was a plastic fan and the chap managed to turn the power off before things got too badly chewed.

  11. #41
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    Quote Originally Posted by shedhappens View Post
    G/day Joe, no I have not fitted one of them, that was just one i plucked from a search for 220v - 380v vfd's.
    This is the one that I fitted to the 5hp Herbert capstan lathe https://www.aliexpress.com/item/3283...27424c4dQHn2FE it works very well.
    Have you checked the output voltage of your 5Hp intallation? You pasted text is from the seller....
    The data I quoted is from the specification page on the manufacturer's website I linked.
    Since that has the same info for your VFD, I believe you are running your 5HP motor on 240V 3-phase, NOT 380/415V. Did you rewire the motor to Delta (if it was 415V Star wehn you got it)? If not, all works well but you are only able to get about 2.8Hp out of the motor. That VFD may have a voltage display option, which will tell you without measuring yourself.
    Have a look at the first line in the table under: "Technology Stadards".
    It says there "Input - 3 phase 380v50/60Hz, single phase 220v50/60Hz, DC voltage" Note: that's three options! DC is allowed by most VFDs as well as AC. They have special DC input terminals.
    Then further down in the line: "Rated output voltage - auto voltage regulation..... " No mention of voltage increase.
    The "wiring diagram" above that table shows a block diagram of the device at the top. Nothing to indicate any voltage transformer, only rectifier and chopper (and brake resistor connections). The manufacturer would make a big point of the voltage increase.
    The prices of these reflect that they are standard VFDs. Voltage transforming ones are at least double those prices.
    BUt as long as you are happy with your motor, all is well.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  12. #42
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    Quote Originally Posted by BobL View Post
    You can ??

    Anyway it looks like he did have the rotor in but it appears he had the fan cover off?
    I've seen a mains cable attacked by a fan - fortunately it was a plastic fan and the chap managed to turn the power off before things got too badly chewed.
    Hi Bob, Guys,

    I've been back and looked at the picture. Yes you are right I didn't register that it was the fan that I could see ! It appeared that the rotor wasn’t fitted.

    Sorry about that my mistake !
    Best Regards:
    Baron J.

  13. #43
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    Quote Originally Posted by jhovel View Post
    The "wiring diagram" above that table shows a block diagram of the device at the top. Nothing to indicate any voltage transformer, only rectifier and chopper (and brake resistor connections). The manufacturer would make a big point of the voltage increase.
    Hi Joe,

    I have to admit that I am not familiar with the VFD models that you are discussing, and only have extremely limited info about them gleaned from the discussion. However, other VFD's have overcome the 230V-415V jump by using voltage doubler type rectifier stages which add an extra capacitor and diode to normal rectifier stage to increase the stored DC voltage available to the chopper stage and output.

    One British supplier purchased TECO 415V VFD's directly and replaced the rectifier stages with voltage doubler rectifiers so they would provide 415V out from 230V single phase input. Their units were effective but expensive, but were a viable last resort option for situations where the motor was heavily intergrated into a machine and could not be replaced with a bolt on equivalent or modded to operate at 230V, (specific discussion at the time related to a drill press with a 2 speed motor integrated into the head and gear box casting.

    It would make sense to design and manufacture units with this feature incorporated if the manufacturer established that there was a market for such a product, and that units leaving the factory in that configuration need not cost much more than equivalent 3P 415V I/O units or SP 230V input/3P 240V output units. I suspect that they could design the PCB's to accommodate all three variants, and simply insert or leave out components, board links etc on the assembly line to establish which variant they are producing. This way, there would not be significant variations in cost prices to produce the different variants.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  14. #44
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    Totally agree with you on every point.
    It's just a question of price.
    Huanyang make those voltage change VFDs too. The price is "normal" industrial level though, not AliExpress "specials" prices...
    The British (ArcEuro) ones you refer to are probably the cheapest you can find, even direct from China....
    The market for 380/415V 3-phase is tiny, btw. Most of Europe has 3 phase in every house, the USA has 115/230V. They are big markets. Most modern motors up to 7.5kW have Star/Delta options, so there are mostly only small markets and older motors to cater for....
    Cheers
    Joe
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  15. #45
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    Quote Originally Posted by jhovel View Post
    Have you checked the output voltage of your 5Hp intallation?
    G/day Joe, to be honest I could not remember checking what the voltage was so I rang my m8 and told him what you said,
    he got his multimeter out and measured 380 volts....... all good

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