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  1. #106
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    Default VFD switching on a Hercus 260

    Josh,
    I'll post a sketch when I get a chance
    Chris
    Chris

  2. #107
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    I am also currently looking for a 3 phase 3Kw VFD with braking and they seem to be double the price as the 240V single phase ones, can't find any used ones either, so have now started making enquiries direct to China.

    Cheers

    Ed..

  3. #108
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    As PDW mentioned, my comments in this thread were in reference to the OP's specific question, however I will choose my words more carefully in future.

    Ewan, as a matter of interest, what size is your motor and VFD, and on what lathe are you running it where it is unscrewing?

    Pete

  4. #109
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    Quote Originally Posted by Pete F View Post
    As PDW mentioned, my comments in this thread were in reference to the OP's specific question, however I will choose my words more carefully in future.

    Ewan, as a matter of interest, what size is your motor and VFD, and on what lathe are you running it where it is unscrewing?

    Pete
    sorry Pete but it read to me that you could not see it happening on any machine with a vfd. I was not making it a competition, just stating that it can be a real problem.
    Lathe is a mars great scott/conrik. Bit bigger than a hercus at 11" x 28" with gap bed. Motor is 2hp, countershaft and flat belt drive, vfd is a huanyang. Faceplate is far the worst if I forget to change the ramp down speed (i have a switch to toggle between slow and fast). Any firm of dc breaking, even coming on a 5hz will cause either of my larger 8" chucks to come free, but not the 5".

    Cheers,
    Ewan
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  5. #110
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    Ewan, yes I can see how my comments could be interpreted that way, however it was meant in context. A 1 1/2" spindle nose on an 11" lathe is quite small, and I'm equally surprised by that. A 260 is 1 3/4 and only swings 10", it also has a much smaller 3/4 HP motor. A 2 HP motor on a lathe such as yours seems rather large. Is this what it was fitted with as standard? What I'm still curious about is how your VFD size compares to your motor size?

    Pete

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    Pete,
    Yes the nose is a bit small. Especially considering it will swing 14" in the gap. The motor that was on it was only .5 hp, I simply put the 2hp on it because that's what I had in 3 phase. I have no idea what the original motor would have been, my countershaft is non original so who knows. I can't really use all the power because of belt slip, especially at lower speeds when the torque is high. The vfd is rated to 3hp but obviously set for 2hp. The machine has its fair share of problems, but cuts well. It really needs a New front bearing, there is not much bronze left in there, but I need the leblond up and running to make it a less painful task. I don't really feel like pulling the head apart half a dozen times just to put it back together to make another cut.
    Cheers
    Ew
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  7. #112
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    Thanks Ewan. Just to close the loop on this. While the OP's question has been answered and hopefully he's a happy camper, I saw no point in commenting further. However I think your situation raises a number of points that are worth mentioning in case others do a search in future.

    In your case you have fitted a motor up to 4 times the original size, and then fitted a VFD that is 50% larger again. Then mention you're spinning off chucks. I think it's a little like fitting a 351 in to a mini moke, and then running on N2O, and complaining that mini mokes smoke up the tyres at every traffic light A normal moke won't do that ... believe me, it was the "company car" for a while ... ok they can be made to squeal a bit The point being that if you step outside manufacturer's recommendations one needs to be aware of the implications that may involve. If the 0.5 - 1 HP motor, as likely specified by the manufacturer, was still fitted and matched to the correct VFD I very much doubt you'd be having these issues. Impossible? No! However without doubt far less likely.

    Likewise I've noticed a trend here that many seem to "upsize" their VFD, presumably in the belief that if a little is good, a lot must be better. Be aware of the potential implications of doing so. A VFD is not a single to 3 phase converter, that just happens to be a function that is incidental in some. Instead they should be considered motor controllers. The correct procedure is to match the same size motor controller to the size motor you're running. That's what they're designed to do. You wouldn't throw a massive carburettor on a lawnmower engine and expect it to run according to the manufacturer's specifications. I suspect fitting a larger VFD than specified for the motor size may similarly allow the VFD to brake the motor hard enough that it may cause an issue with a screw on chuck. I'm not au fait with the most modern controllers, and they may now be smart enough to avoid this scenario, but the safest path, as always, is if in doubt do what the manufacturer recommends.

    Hopefully that clarifies all this. Alternatively makes it as clear as mud. The bottom line is match your motor to the machine, and match your VFD to the motor. Doing so should help avoid all sorts of future complications.

    Pete

  8. #113
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    Quote Originally Posted by Pete F View Post
    Thanks Ewan. Just to close the loop on this. While the OP's question has been answered and hopefully he's a happy camper, I saw no point in commenting further. However I think your situation raises a number of points that are worth mentioning in case others do a search in future.

    In your case you have fitted a motor up to 4 times the original size, and then fitted a VFD that is 50% larger again. Then mention you're spinning off chucks. I think it's a little like fitting a 351 in to a mini moke, and then running on N2O, and complaining that mini mokes smoke up the tyres at every traffic light A normal moke won't do that ... believe me, it was the "company car" for a while ... ok they can be made to squeal a bit The point being that if you step outside manufacturer's recommendations one needs to be aware of the implications that may involve. If the 0.5 - 1 HP motor, as likely specified by the manufacturer, was still fitted and matched to the correct VFD I very much doubt you'd be having these issues. Impossible? No! However without doubt far less likely.

    Likewise I've noticed a trend here that many seem to "upsize" their VFD, presumably in the belief that if a little is good, a lot must be better. Be aware of the potential implications of doing so. A VFD is not a single to 3 phase converter, that just happens to be a function that is incidental in some. Instead they should be considered motor controllers. The correct procedure is to match the same size motor controller to the size motor you're running. That's what they're designed to do. You wouldn't throw a massive carburettor on a lawnmower engine and expect it to run according to the manufacturer's specifications. I suspect fitting a larger VFD than specified for the motor size may similarly allow the VFD to brake the motor hard enough that it may cause an issue with a screw on chuck. I'm not au fait with the most modern controllers, and they may now be smart enough to avoid this scenario, but the safest path, as always, is if in doubt do what the manufacturer recommends.

    Hopefully that clarifies all this. Alternatively makes it as clear as mud. The bottom line is match your motor to the machine, and match your VFD to the motor. Doing so should help avoid all sorts of future complications.

    Pete


    Pete, the size of motor and VFD entirely depends on what you want to do. There is no "right" or "wrong" size. There are some less than ideal size combinations, though.

    Let's first look at the relationship of motor size to VFD size. It is common practice to choose the VFD one or two sizes larger than the motor. This is so, because VFD's are not rated at the highest possible chopper frequency, nor are they rated at the highest ambient temperature you can expect in a non air conditioned workshop. If you mate say a 1HP motor to a 1HP VFD, your resulting drive (drive = combination of motor and VFD) will probably only have 3/4HP if you choose to run your VFD at its highest chopper frequency (the higher the chopper frequency, the bigger the losses but the less audible noise). Now if you additionally want to run your drive in summer in a shed, you may find out that the temperature inside the VFD enclosure may rise after a very short time some 10 or 15 degrees above ambient temperature, and if the ambient temperature is already 40C, your drive will throttle back its output to some 1/2HP. That is NOT a very good result, if you initially were about to replace a conventional 1HP lathe motor! But it would be a perfectly reasonable result, if you were initially to replace a conventional 1/2HP lathe motor.


    So if you have a lathe with say a 4 speed gearbox and conventional 1HP motor, and after taking the above into account, it would make sense to match the motor with a 1.5 or 2HP VFD. The end result is still only a 1HP drive. But now, what if the intention was to completely do away with the 4 speed gearbox? In this case you will need a 4HP drive to have the same power available that you had with the 1HP motor at the lowest speed setting. It is like if you are trying to drive up a very steep mountain in your car in 4th gear, you need a much more powerful engine to keep up with the same car in 1st gear. In above example, you will need a 4HP motor with a 6HP VFD to run your 1HP lathe without gearbox. That is what is done in industry, that is why you see lathes with such high HP drives, because if you run a CNC lathe, you do not want to stop the software and ring a bell whenever it needs your assistance to change gear. It is expected that the lathe can cover the whole speed range, with always enough power reserves to remove metal at an efficient rate. Chris

    PS: if you have problems with old threaded spindle noses, you can reduce the braking ramp, or install a locking collar or even a simple locking grub-screw. Hell, the chuck coming off a threaded spindle is nothing new that did not exist before VFD's came along. It happened already 100 years ago, long before VFD's existed. You just had to "plug reverse" a 3 phase lathe. That is why they first invented chuck locking collars, and lather abandoned threaded spindle noses in favor of camlock.

  9. #114
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    Chris I'm curious to see the specifications of other VFD manufacturers. While I'm very happy with the SEWs* I'm obviously keen to know about alternatives. Can you provide a link to a manufacturer's specifications where they recommend an installation where the VFD is 2 sizes larger than the motor?

    Most of my Sew's are now a little dated and I'm sure there's been some progress in this area, but I have 4 of one type (one isn't used, plus a later model) and this is a direct cut an paste from the manual:
    Factory setting: Rated motor power in kW corresponding to the rated inverter power
    If a smaller or a larger motor is connected (maximum difference one frame size), then a value must be selected which is as close as possible to the rated motor power.

    The later one is a quite vague in this area. Note this is my highlighting. On that model you can't even select more than 1 frame size difference! These inverters are rated to 50 degrees under all selections, with a 150% overload factor.

    Pete

    * The reason I am so sold on the SEW Eurodrive is not only the expected German level of manufacturing, but the extraordinary support. When I received my first one it was tripping my RCD and it was clearly not acceptable. A few emails and phone calls to real live engineers in Melbourne, who stuck their neck out in explaining the problem was earth leakage due to the input filter capacitors they have fitted to meet CE requirements, and how I could go about removing them. What may have been a tricky problem to diagnose was fixed very quickly in actually modifying their gear. It scored 10/10 in my mind as it seems support like that is now the exception.

  10. #115
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    Quote Originally Posted by Ueee View Post
    Pete,
    Yes the nose is a bit small. Especially considering it will swing 14" in the gap. The motor that was on it was only .5 hp, I simply put the 2hp on it because that's what I had in 3 phase.
    FWIW I once started spinning the chuck loose on a Premo lathe (bit bigger than a Hercus but not a lot) that I'd fitted with a 1 HP 3 phase motor. As I had 415V power, no VFD and this was 30 years ago anyway.

    I plug-reversed the motor )

    Once.

    Fortunately I slammed it back into forward before the chuck played bouncey around the shop.

    Next I machined the backplate off of the spindle (because it sure as hell wasn't coming off any other way), all the while contemplating my stupidity.

    So I have no difficulty believing that this can happen depending on the circumstances.

    PDW

  11. #116
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    Josh,
    Here's my wiring diagram. For this to work I needed to enable 3-wire control and select LI3 as the reverse command input. I haven't shown the speed control pot as that's dead easy to wire up.
    Chris
    Attached Images Attached Images

  12. #117
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    I still have one logic input free. I'm thinking of using it for jog control. Seems easy enough to set up. How many of you guys use jog?
    Chris

  13. #118
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    Quote Originally Posted by Pete F View Post
    Can you provide a link to a manufacturer's specifications where they recommend an installation where the VFD is 2 sizes larger than the motor?
    Pete, since this is Chri's thread, and he just bought and installed a Telemechanique Altivar 12, I give you the link to the Altivar 12 operator manual:
    http://www.taco-hvac.com/uploads/Fil...2_bbv28581.pdf

    Download it, and look on page 13, you will see the derating graphics chopper frequency vs. temperature, this is a screen shot of the manual:

    ATV12page13.jpg

    This is a screenshot of page 10 with the drive ratings. Towards the bottom is an explanation on how to interpret the ratings. According to it, the nominal power needs to be derated by 30% if you wish to use the higher chopper frequency of 16kHz:

    ATV12_p10.jpg

    Similar derating information can be found in most drive manuals, even my oldest 2002 German Lenze is like this, my Siemens etc. It is just common practice for even the most reputable VFD makers to rate their drives at a low chopper frequency and ambient temperature. This so because the buyers (that is us) compare price for a given KW rating, and thus any VFD maker giving ratings at more realistic conditions would put themselves at a market disadvantage.


    Here something different I like you to take a look, a screenshot of page 85:

    ATV12_p85.jpg

    It is about the storage warning at the bottom. Few VFD makers are honest enough to put this in their user manual. It is important for people like us, that are not unlikely to purchase "New Old Stock" VFD's to save money. If a VFD was in storage for a couple years or more, the big electrolytic bus capacitors need to be slowly "reformed" or they may burst and leak. This is best done with a variac transformer. Chris

  14. #119
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    Default VFD switching on a Hercus 260

    Just out of interest, I found the squeal at 4kHz quite annoying, but at 5kHz quite acceptable. After my next hearing test I'll work out which frequency my hearing is most degraded at and set that on my VFD!
    Chris

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    Quote Originally Posted by cba_melbourne View Post
    Pete, the size of motor and VFD entirely depends on what you want to do. There is no "right" or "wrong" size. There are some less than ideal size combinations, though.

    Let's first look at the relationship of motor size to VFD size. It is common practice to choose the VFD one or two sizes larger than the motor. This is so, because VFD's are not rated at the highest possible chopper frequency, nor are they rated at the highest ambient temperature you can expect in a non air conditioned workshop. If you mate say a 1HP motor to a 1HP VFD, your resulting drive (drive = combination of motor and VFD) will probably only have 3/4HP if you choose to run your VFD at its highest chopper frequency (the higher the chopper frequency, the bigger the losses but the less audible noise). Now if you additionally want to run your drive in summer in a shed, you may find out that the temperature inside the VFD enclosure may rise after a very short time some 10 or 15 degrees above ambient temperature, and if the ambient temperature is already 40C, your drive will throttle back its output to some 1/2HP. That is NOT a very good result, if you initially were about to replace a conventional 1HP lathe motor! But it would be a perfectly reasonable result, if you were initially to replace a conventional 1/2HP lathe motor.


    So if you have a lathe with say a 4 speed gearbox and conventional 1HP motor, and after taking the above into account, it would make sense to match the motor with a 1.5 or 2HP VFD. The end result is still only a 1HP drive. But now, what if the intention was to completely do away with the 4 speed gearbox? In this case you will need a 4HP drive to have the same power available that you had with the 1HP motor at the lowest speed setting. It is like if you are trying to drive up a very steep mountain in your car in 4th gear, you need a much more powerful engine to keep up with the same car in 1st gear. In above example, you will need a 4HP motor with a 6HP VFD to run your 1HP lathe without gearbox. That is what is done in industry, that is why you see lathes with such high HP drives, because if you run a CNC lathe, you do not want to stop the software and ring a bell whenever it needs your assistance to change gear. It is expected that the lathe can cover the whole speed range, with always enough power reserves to remove metal at an efficient rate. Chris

    PS: if you have problems with old threaded spindle noses, you can reduce the braking ramp, or install a locking collar or even a simple locking grub-screw. Hell, the chuck coming off a threaded spindle is nothing new that did not exist before VFD's came along. It happened already 100 years ago, long before VFD's existed. You just had to "plug reverse" a 3 phase lathe. That is why they first invented chuck locking collars, and lather abandoned threaded spindle noses in favor of camlock.

    Hi cba_melbourne,

    I agree with your logic for choosing larger VFD's nothing wrong with that, but it's not normal practice to choose a larger VFD, my experience is that the vfd is chosen to suit the motor, end of story. The main reason being cost, customers don't appreciate having to pay extra for something they don't need. For small VFD's like we are discussing, it's neither here nor there, but price goes up on a very steep curve for larger drives. Josh has designed switchboards, wired up and configured many thousands of drives so he can add his comments ( if he feels so inclined).

    What Pete may be referring to is specific to vector drives, where the drive software parameters need to match the motor parameters, some drives have an autotune function to measure various motor parameters and set them accordingly. A motor that's close to the drive rating might afford better vector control, This is vastly different situation to, say, a grossly oversized V/F drive...

    Temperature ratings are always a problem when you have high ambient temperatures, I did a lot of temperature logging on Danfoss drives, ( 250kW mostly ) logging heatsink and control board temperatures, Ive never seen a drive that reduces it's output when the temperature rises? Except when the over temperature alarm trips and then the output reduces to zero...

    With the intermittent nature of lathe usage, I'd be very surprised if temperatures became a problem for the average user.

    Regards
    Ray

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