Need help setting up a large lathe (air interlock)

Discussion in 'Tools' started by Entropy455, Jul 25, 2018.

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  1. Nov 13, 2018 #41

    Entropy455

    Entropy455

    Entropy455

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    I haven't ordered contactors yet. I appreciate your (and other's) help. Continued input is welcome. . ..

    Another option I have is to use high-current SSRs, which are inexpensive (about 40 dollars, in lieu of hundreds of dollars for contactors). The problem is that SSRs generate 1.5 Watts per ampere, and I need (qty 2) per converter. Basically I'll be dumping 600 watts into a heatsink when the lathe/converter are running. On the plus side, there's no moving parts with SSRs. I don't want to go the SSR route, but I don't want to spend 1.5 grand on contactors either. Used or old non-used surplus might be my best route.

    I'm going to order the parts I know I need - starter caps, run caps, supply breakers, etc. I still need to build a frame for the motors, and pull a permit for the second 200 amp panel in the shop - thus I've got a little time to continue shopping for contactors. . . .
     
  2. Nov 13, 2018 #42

    ignator

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    I always search eBay 'price plus shipping lowest first' I saw those SSRs, in 3 phase. I'd worry about overload, and them blowing short. And there are so many counterfeit SSRs from China using name brand logos. 600watt heatsink is crazy dissipation. I've only used them in the shop for 3Kw radiant heaters, and just bolt them to an aluminum sheet. I had one of the Fotek brand counterfeit fail last year and it was 25amp rated, 2x the load current.
    Is your RPC design to start one of the motors, then use the generated phase to start the 2nd motor? I've never looked at multiple motor RPC topologies.
    I assume your in the Seattle area, and get to work through winter without frozen ground. My wife's parents lived up in Anacortes.

    I tripped on this from eBay
    https://www.ebay.com/itm/30KW-40HP-...h=item28638455d6:g:9DYAAOSwDkVaF-On:rk:5:pf:0
    I was shocked to see this with single phase input. I know this is not your path.
     
  3. Nov 14, 2018 #43

    Entropy455

    Entropy455

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    The first 40 horsepower converter will start automatically - with one contactor for switching power, and another for engaging the start capacitors. The second converter will start off the first, with just one contactor switching power. The generated legs are hard-wired, thus no starting caps are needed to start the second converter. Both converters will have run caps installed, sized for taming the voltage on the generated phases. The load "should" be balanced between the two converters - seeing as they're identical impedance (i.e. matched motors).

    My biggest fear of SSRs is they tend to fail closed. . . .

    People love the new variable frequency drives with soft start. I must admit, I'd probably fall in love with them too - if I had one. . . Another problem with a fancy digital motor controller for my lathe, is that I've got at least three 3-phase motors - one 40 horsepower for the spindle, and two smaller motors - one for the coolant, and one which I'm assuming is for a pressurized headstock lubrication system. Don't get me wrong, the obstacle of powering the smaller motors separately could be overcome - but I'm going to stick with an old-school solution nonetheless - i.e one large rotary phase converter.
     
  4. Nov 15, 2018 #44

    ignator

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    I understand, I was more shocked to see a 40HP VFD with single phase input. I've never seen this before. Everyone required 3Ph input, and would not operate because of a phase loss detector. I think this seller also indicated it was a sensorless vector drive, which is a requirement (for high torque low speed operation) from my experience.

    I used a 2nd VFD that was cheep (fractional HP) for the coolant pump on my lathe. But I've never put any coolant in the sump. Just seems messy. I've only ever used it on the mill when doing side milling with an end mill in steel (after burning up a few). I use oil coolant (Mobil Gamma), as something about water soluble stuff seems like a recipe for rust, if you don't remove the setup and wipe down the table (as well the biological experiment in the sump). The oil splatter on the floor was remembered, strange thing the stuff that didn't get cleaned up, evaporated within a week. The other issue I have with coolant, is the vaporized smoke, I believe this is very bad for your lungs. Yet I see many youtube videos of pros having a closed shop with smoke in the air.
     
  5. Nov 15, 2018 #45

    Entropy455

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    I'm going to hijack my own post, and ask a VFD question -

    Is an inverter-duty, and vector-drive rated motor the same thing? I.e. must an electric motor be rated for inverter-duty/vector-drive, when used with a VFD?

    The reason I ask - my little lathe (on page one of this thread) came with an old-school VFD, it works ok. . . . At lower speeds the motor torque basically disappears. It's a somewhat variable speed motor. I know that I'm not supposed to take heavy cuts on a little lathe, but the darn thing has trouble cutting plastic it's so underpowered. My plan is to eventually put a DC motor on it, with a PWM. However I'm starting to think a VFD with 3 phase is the way to go.

    Must I purchase an inverter duty motor, or will a quality heavy-duty 3-phase motor work?
     
  6. Nov 15, 2018 #46

    Wizard69

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    I understand your need for high amperage contractors but please avoid any of the Chinese offerings. The few Chinese controls I’ve worked with have been crap.

    Your capacitor inrush current will be huge, it may pay to create a precharge / soft start solution with some really large resistors. Having a contractor blow up is no fun at all. The worse one I saw was due to a rotor lock up on a 30 hp compressor. The capacitor bank just makes your startup currents even worse so having a bit of margin is in order.
     
  7. Nov 15, 2018 #47

    Entropy455

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    I'm half tempted to go old-school and use some giant knife switches - and simply polish off flash marks with sandpaper every few months. . .

    My 10 horsepower converter has 80 amp contactors, which seem to be holding up just fine.

    I'd like to find some 700 or 800 ampere contactors (obviously used) - which would provide plenty safety-factor.
     
  8. Nov 15, 2018 #48

    ignator

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    Yes inverter-duty and vector-drive are the same thing (vector drive should have an encoder for position control, otherwise it's just semantics). The difference (between standard motors and inverter duty) is better electrical winding insulation.
    I've had very good luck with old antique motors, and modern VFDs, which control the edge rate so they are not overly fast. This limits the voltage spikes that cause electrical insulation failure. I have a 1940's motor that is part of a Lima overhead drive line attachment to my 1930's Rockport horizontal mill. I don't use this machine too much. My vertical mill has a 1960's motor, and 100s of hours of time using a Hitachi VFD.
    This has been my understanding of the issues when VFDs first came to the market place, their edge rate was too fast.

    I've said this recently about sensorless vector VFDs, they produce lots of torque at very low Hz drive of the motor. I learned this by purchasing TECO standard VFDs included with a 1HP inverter duty motor 20+ years ago. The drives would cog the motor shaft (jump discrete movements) and would stop spinning the motor below 20Hz or so.
    Check out below link for motor and VFD packages. I've found them to typically have the best prices on quality VFDs.
    https://dealerselectric.com/motor-drive-packages.asp
     
  9. Nov 15, 2018 #49

    Entropy455

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    Dealerselectric does have freakishly low prices. Thank you very much for the link.

    https://dealerselectric.com/Package-NAT1-5-18-56-and-L510-202-H1-U.asp

    Assume for the moment I purchase the above combination for my small lathe. The advertised frequency is 0-650 Hz. First obvious question - is it safe to turn a 1,800 rpm motor at 19,500 rpm? My assumption is absolutely not - thus what is a safe upper speed? 3,600 rpm? 4,500 rpm?

    If I assume 4,500 rpm is the safe upper speed for the motor, I could direct-couple the motor to the spindle with a 2.25:1 pulley reduction, which would give me a spindle speed from 1200 rpm, down to ??? I.e. what is the expected low-end performance??? The literature is silent (or I simply don't know where to look) . . .
     
  10. Nov 15, 2018 #50

    ignator

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    I always set up the VFD for max 3600 RPM. Basis is that the same rotor is used for 4 pole as 2 pole, so it is designed to operate at 3600.
    The L510-202-H1-U manual has one section for setting the drive up for sensorless vector page 4-21 of the manual. SLV mode. I've not used this model of TECO.
    https://www.tecowestinghouse.com/Manuals/L510_instruction_manual.pdf
     
  11. Nov 15, 2018 #51

    Entropy455

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    The motors being sold in the inverter/motor combination packages at dealerselectric are not specifically inverter-rated. What are the implication of this? Is motor life simply reduced? Is the significant wear & tear on the motor from sustained low rpm operation, or is operation at any rpm hard on the motor with a digital drive?

    Here's where I'm going with this - the 40 horsepower inverter you linked in post #42 would likely power my lathe, maybe from a single 200 amp panel (rated input current is not listed anywhere). In theory, I could use my existing 10 horsepower rotary phase converter to power the coolant pump & lubrication pump - and electrically separate the 40 hp spindle motor onto the inverter. At 1500 bucks, this is a much better cost option than building an 80 horsepower converter. I had no idea inverters were available so large, and so inexpensively.

    The big question is this - do I need to replace the 40 horsepower motor in my lathe with an inverter-rated motor, or can I use the stock motor? If replacement with an inverter-rated motor falls under the "should replace" or "must replace" category, I'm back to building a rotary phase converter - because a 40 horsepower inverter-rated motors start at about 4 grand. . .
     
  12. Nov 16, 2018 #52

    ignator

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    The big thing with VFDs is to not have a long connection between the motor and the VFD as the long connection enables a larger standing wave peak voltage. This voltage is what damages the motor winding insulation. My connections are less then 6 feet.


    Here is one such article for input;
    https://www.energy.gov/sites/prod/files/2014/04/f15/motor_tip_sheet14.pdf

    I did an internet search using "are inverter duty motors required for VFD connection".

    I doubt that you will ever use the 40HP of the lathe, but I don't know if you intend to use that oil well lathe for commercial removal rates. The inductive reflection voltage is a function of the current pulse value, so low torque operation keeps the V=L di/dt impulse voltage within the insulation of the motor. Also operation with 220VAC, keeps these peaks lower then if 440VAC operation is used.
    I really don't think you will have any problems unless you push the lathe cutting power to the limits of the motor, and using 440 operating voltage.
    Newer standard motors have improve varnish winding insulation. Your 1960's 40HP is such a motor.
     
  13. Nov 16, 2018 #53

    Entropy455

    Entropy455

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    I've been reading up on the high voltage spikes associated with long wire runs. If I mount the inverter on the side of my late (adjacent to current control panel), my wire run to the motor will be about 5 feet max.

    I'm going to give this a shot. An added bonus is that I might not have to install a second 200 amp power panel (or purchase 1500 dollars worth of contactors).

    And look at the bright side - if I do burn out the lathe motor, I've got two nice 40 horsepower ready-spares. . . . .
     
  14. Nov 16, 2018 #54

    ignator

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    I integrated my VFD to use the apron mounted FWD/REV lever. As well the foot brake stops the VFD.
    I never made a drawing of this, but I know that the VFD is connected directly to the motor so the FWD/REV contactors are not used.
    Switching the connection between the VFD and motor is forbidden. Voltage spikes large enough to blow up the output transistors can occur.
    I see the vendor on eBay will furnish a user manual if you message them. That may be worth seeing how well it's been translated to understandable usage by you.
    Sorry I interrupted your project. Oh, and the shipping is ~$275, don't know if you your ebay page shows this.
     
  15. Nov 16, 2018 #55

    Entropy455

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    I'm not upset about changing my design plan.

    A VFD is obviously a better route. My failing to recognize this would make me a grumpy old man - and I'm not there yet. . . . .
     
  16. Dec 2, 2018 #56

    Entropy455

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    I'm hesitant to purchase the VFD from China (Part number V8-G 2S 30R0G).

    The price is good (almost too good to be true). A VFD that will drive a 40 horsepower motor with single phase input is rated for 100 horsepower on 3-phase. These 100 HP units are quite large, and quite expensive ($3,500 typical starting price).

    I'm worried that the V8-G 2S 30R0G unit from China will be rated for 40 HP with 3 phase input power, and actually only 15 HP with single-phase input. It might be worth it for me to simply pay double, and purchase a 100 HP unit now - one that I know will drive a 40 HP motor with single phase input power. . . . . The China unit cannot be returned, and I do not like to purchase parts twice. . . .

    I'm going to request the V8-G 2S 30R0G manual nonetheless - to see if there's any fine print on the input-power performance. My gut tells me the VFD route will cost closer to 4 grand. Is it worth it????
     
  17. Dec 2, 2018 #57

    gunner312

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    Axleson is an OUTSTANDING machine, I used to run one that was about the same size but that was a few years ago. Great machines right up there with Cincinati and Clausing-Colchester. One thing I remember is that the spindle bore was about 8" great for doing shafting. I don't have anything that big anymore, but I have a Wam that needs 440 and I use a 220 3phase converter to a 440 Transformer to power it up but then it's just 10 HP. Most of the time the Air interlocks are low pressure (As I remember or mis-remember as the case may be, usually about 45 PSI but could be as high as 90 psi) The reason for low pressure was so that when the system was under heavy use, you could still run the lathe as long as pressure was above 45 psi. Outstanding Machine. I just sold my big lathe it was only 24 X 144. Good luck
    with the Axleson.
     
  18. Dec 2, 2018 #58

    ignator

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    My reading of many posts about VFDs is that you have to double the HP rating to ensure the input rectifier is large enough for single phase.
    I see in their eBay auction listing a diagram that someone took the time to show a single phase circuit breaker connected to this VFD.
    http://rover.ebay.com/rover/1/711-5...0001&campid=5338413729&icep_item=173468308950
    I've repeated the link here for others to see the item.
    If you can find a 40HP VFD with the DC bus available as terminal connections, you can add your own single phase rectifier and capacitor filter and not use the built in diodes. I don't see this on this on this drive.
    I do understand your hesitation, as $1650 is not cheep. But China can do that price as they don't pay their Engr's the same pay scale, and their overhead has no comparison to any first world country.
    Hope they provide a manual in PDF via a message link. And it's translation validates single phase input at rated current.
     
  19. Dec 3, 2018 #59

    Entropy455

    Entropy455

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    This I can do - a full-bridge rectifier, a healthy bank of capacitors, and a series-choke for voltage spikes.

    I found a link for sizing VFD power supply capacitors for single phase applications: https://kebblog.com/select-single-phase-vfd/

    The question is - are there VFDs were the DC bus is accessible for normal external power connections? I suppose I could always open the unit up, and jumper to the backside of the rectifier.

    Another question: the 40 HP VFDs on dealer's direct - some of them are advertised for pumps and fans, where others (more expensive) mention lathe applications. Will these entry-level VFD advertised for pumps and fans work satisfactorily? Example: https://dealerselectric.com/F510-2040-C3-U.asp I honestly don't need super fancy control features - I just need the ability to start & stop my lathe. . . . That being said - not having to modify the VFD internals would be a plus also (i.e. having a terminal connection for external power supply).
     
  20. Dec 3, 2018 #60

    ignator

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    I've found this same VFD on Aliexpress;
    https://www.aliexpress.com/store/pr...phase-0-380V-out-60A/1155094_32842700732.html
    This shows the same artwork and also indicates single phase power input.
    I've found the 400VAC class of this drive with 3 phase in for $613, but could not find the 2ooVAC class with single phase input, for a low cost. You may find it for a lower cost with your search.
    https://cntopstock.com/30kw-40hp-30...vac-input-3phase-0380v-output-60a-p-4856.html

    First Q; Yes, the manual will have this detailed. I've seen this on my 10HP TECO 7200 drive. And the harder way would be to open the unit up and connect into the existing bus, probably difficult to do with the large current and keeping the connection solid and low resistance.
    upload_2018-12-3_11-22-43.png

    Second Q;
    The fans and pumps VFD only have V/f control, as they do not need to provide high torque at low RPMs, as with fans and pumps the torque drops off with speed. This sort of drive will work perfect for lathe operation if you don't run the speed down to single Hz, and want high torque. This drive still provides soft start.
    The other control is sensorless vector control (there are others that use encoder feedback) and this provides up to 200% of torque at near zero Hz. And as you've found they charge extra.


    From all my looking at this eBay drive and the same on Aliexpress, and sites that show phase converter VFDs, I think you can trust the single phase input description as accurate.
     

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