VFD as a 3 phase source
Close
Login to Your Account
Likes Likes:  0
Results 1 to 12 of 12
  1. #1
    Join Date
    Jan 2005
    Location
    Duluth, MN
    Posts
    507
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    45

    Default VFD as a 3 phase source

    Just bought a 14-1/2 inch South Bend made in 1965. This lathe came from a trade school and seems to be in good shape. All original-3J-4J-telescoping taper attachment-L-00 spindle nose-2 HP 3 phase motor-Hand Wheel 5C collet setup. Purchased lathe from the course instructor. The school now has mostly Haas equipment.

    Vintage Machinery has a full line 1966 South Bend catalog. The catalog shows 3 HP motor as an option. Catalog also shows optional maximum speed of 1200 RPM instead of 845 stock. I'd like to run insert tooling and thus the interest in more power and speed. According to the catalog the lathe with motor is right at a ton.

    Stock drive line configuration has 4ea. narrow V belts driving the shaft that carries the lower cone pulley. The motor pulley is quite small. If I go to a 3 horse I could change the two pulleys and achieve the desired spindle speed. I could also go to 2 groove pulleys and wider V belts.

    Conversely, I can use the VFD to achieve the same speed by dialing in about 85 HZ. Is one method appreciably better than the other?

    Is it easy to wire in an emergency stop button?

    Thanks,
    Larry

  2. #2
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    27,310
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8516

    Default

    Quote Originally Posted by Larry on Lake Superior View Post
    Conversely, I can use the VFD to achieve the same speed by dialing in about 85 HZ. Is one method appreciably better than the other?

    Is it easy to wire in an emergency stop button?
    eStop buttons are cheap to buy - five bucks or so on-up - and easy to wire, VFD or any other power.

    BE AWARE hardly ANY can actually stop at an "emergency" rate on anything less than DC plugged, 4Q DC Drive, or - best of all - electric motor brake.

    Mostly, they just "coast-down", same as the "OFF" on a drum switch or "STOP" on magnetic starter already does. Other than adding an eStop for a faster to reach location - or two, there's not much gain.

    Better to add a switch PLUS a mechanical brake off a foot-stomp bar if you are concerned. Many lathes have those OEM, Asian, and European especially, and for half a century and more.

    VFD's have finite service lives. At typically 7 to 12 years they "should have" new capacitors, generally get replaced around half-again that life, maybe double - instead. Cheaper that way. And "Oh, BTW?" those lifespans - in the manuals - are for VFD run off THREE PHASE inputs. Ones for converting off single-phase have to work a bit harder, may or may not last as long. The manuals are free, online, as .pdf's.

    "RTFM" first, then buy one specifically rated for work off 1-P by the maker.

    Best to buy NEW with VFD, not used, BTW. Where d'you think the used ones came from?

    Got it in one.

    Industrial pulls for scheduled preventive maintenance, overage capacitors "coming due", mostly!

    Old motors are vulnerable to VFD, live longer off an RPC, which itself has a 20-year or better life span. Simple-dumb, work well, last a long time. RPC do.

    If you really want a VFD for variable speed, best to also put a new motor with it that is rated for "inverter duty". it will also have its min and max frequency and RPM right on the nameplate.

    Marathon "Black Max" are well regarded for that, even bought used, but lots of folks make decent 3-P motors.

  3. #3
    Join Date
    Jan 2005
    Location
    Duluth, MN
    Posts
    507
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    45

    Default

    Thermite,
    Thanks for your reply. RTFM is an acronym I'm not familiar with-is the M for manual?

    You've given me lots to think about. Maybe I'll buy a NEW VFD rated for 3 HP and just run the old girl as is. After all it's been working for 50+ years. I can swap the 2 for a 3 HP later on if desired.

    How did you choose your user name? I worked in the corrosion protection field for many years. We used thermite welds to attach magnesium sacrificial anodes to our gas mains. IIRC the brand name was Cadweld. The system used a small graphite crucible with a hinged top. A thin concave disc was placed at the bottom of the melt chamber. The thermite charge was poured in and the top was closed and the flint spark ignitor started the fireworks. The disc melted in a flash and the molten iron flowed down to attach the wire to the gas main. It worked well as long as the thermite charges were properly stored.
    Thanks again,
    Larry

    P.S.--The catalog offered brake motorsat a substantial premium.

  4. #4
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    27,310
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8516

    Default

    Quote Originally Posted by Larry on Lake Superior View Post
    Thermite,
    Thanks for your reply. RTFM is an acronym I'm not familiar with-is the M for manual?
    R ead T he F ine M anual, or "somethign like that", yes!

    You've given me lots to think about. Maybe I'll buy a NEW VFD rated for 3 HP and just run the old girl as is.
    Also buy a "dv/dt" filter 3% or better - or a "pure sine wave" filter - load side, to protect the old motor, then. 3-Phase, of course. And used is fine for those. Sine is more expensive "usually", but might be cheaper by accident, used.

    How did you choose your user name?
    Lack of imagination. Didn't think to use my OWN name at the time because I didn't realize a PM USRID could embed SPACES, so few others were!

    G'Dad was B&O railroad, 44 years, Dad & I both Combat Engineers. TherMATE, rather than TherMITE is one of our most-favoured cutting charges, damaged steel structures most of all.

    It was Dad who dropped that failed bridge, Morgantown/Westover, WV into timber-protected river barges without risking a welder's life nor breaking any windows with HE.


    P.S.--The catalog offered brake motorsat a substantial premium.
    I have a DC one... with an AC brake, yet! The guts of those brakes are also used on automotive air-con compressors (12 VDC), same again mowers and groundskeeping machines as clutches. Salvage is possible. Ebay also has those as NEW repair parts.

    The ATV / RV market has mechanical brakes, air, hydraulic, cable or lever. Internal drum, external (band) drum, and disk.

    Hardinge uses CORKS - "buttons" about the same diameter as corks used for wine bottles.

    My French HBX-360-BC uses a Vee-belt pulley with a partial belt anchored at one end. Foot treadle and linkage rods pull the other end down into partial "wrap" and the pulley acts as brake.

    That one right there may be the easiest and cheapest way to ADD a mechanical brake.

  5. #5
    Join Date
    Jan 2005
    Location
    Duluth, MN
    Posts
    507
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    45

    Default

    I too had a French lathe. Mine was a HES-16(aka Cholet-435). Beautiful machine and less exotic than the Cazeneuve. The spindle brake was the same but used a flat instead of V belt. The wedging action of the V must make for very quick stops.

    The HES is a great lathe-lovely design and execution. Mine was a stripper model that lacked a clutch for the spindle. The motor was optimistically rated at 15 HP. I ran the lathe on a 35A fused circuit without incident but I never used anywhere near full power. When I owned the lathe I lived in Duluth MN right across the river from Superior WI. This area is very depressed economically-especially Superior. I was able to rent a 1100 sq. ft. shop with my own bathroom and a 10 ft. wide overhead door opening onto a concrete driveway for $350/mo. plus utilities. Admittedly the neighborhood was bad and the roof leaked but the price was right.

    Dementia and a broken hip forced us to relocate back to Minneapolis to be near child and grandchildren. Our move was 3 years ago. My wife passed 3 months back. I'm starting anew with my hobby-I hope it will fill my days gainfully.

    Thanks,
    Larry

  6. #6
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    27,310
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8516

    Default

    Quote Originally Posted by Larry on Lake Superior View Post
    I too had a French lathe. Mine was a HES-16(aka Cholet-435). Beautiful machine and less exotic than the Cazeneuve. The spindle brake was the same but used a flat instead of V belt. The wedging action of the V must make for very quick stops.
    Later HBX got all elegant and Parisian movie-star like, switched-over to a real disk brake with hydraulic puck... but that simpler one on mine warms the cockles of my redneck farm-boy heart.

    Never seen a BAD lathe or mill out of France, either one. Strange world-view maybe. Poorly made, never.

    LOVE their breads. Best part of Escargot is the butter, and I only ever et a mess of frogs' legs but the one time, anyway. Bland as can be. Squirrels at least have some flavour to 'em.

    Some days, I even suspect Henri Rene Bruet HIRED squirrels as designers rather than eat of 'em.

    It's France. They'll have had a bitchin' strong Union Local..


  7. #7
    Join Date
    Aug 2010
    Location
    Tucson, AZ
    Posts
    213
    Post Thanks / Like
    Likes (Given)
    6
    Likes (Received)
    54

    Default

    Single phase VFDs are common and reasonably priced up to 3 Hp. Beyond that typically one uses a 3 phase input derated to for single phase operation so a more expensive proposition. As far as capacitor life, better designed VFDs these days will last a long time, on the order of 20-25 years for something like the Hitachi drives, Yaskawa 25+ years. Capacitors are not user replaceable in these smaller units, so really a non-issue these days. You have more issues with capacitors when the VFD's sit on the shelf for years without being powered up. I built a VFD system for a SB13 last year and it performed very well, the motor was replaced.

    If you want quick stopping you need an external braking resistor and a VFD with the circuitry to use an external braking resistor. Limitation in braking is more slippage (belts/clutch) in the drive train and rotational mass X speed. A motor brake will not stop you faster and is much more expensive. Newer design 14" lathe I use electronic braking with stopping in 1.0-1.5 seconds. There are limitations to how fast you can stop/reverse a threaded chuck spindle w/o a lock, which is not an issue with the a locking spindle nose. If incorporating a manual foot brake in addition to electronic, it requires a free run command to the VFD when using the manual brake and a control system that kills the run command.

    Older motors are less tolerant of running them off of VFD's which typically require a lower switching frequency and more conservative motor parameters. An output filter could be used, but a waste of money and space vs. getting a newer motor. At 3 Hp, unless you want to maintain the vintage look, replace the motor with an inverter rated/newer motor and you will not have to deal with the annoying motor whine of lower switching frequencies. Typical 1750 RPM 3 phase motors will easily handle 2X their base speed, so no issues with dialing it up motor speed. This also gives you a wider operating window using the VFD speed pot. There are some performance difference Hp/Torque depending on the motor frequency.

    VFD's are directly wired to the motor, so a VFD is not a 3 phase frequency source that you connect to your machine and everything works as before. VFD have programmable low voltage inputs that control the VFD functions, you should use some control system design that prevents run/restarts after power loss and some forms of safety interlocks. If you want something that is plug and play then use an RPC.

    As far as higher spindle speeds for carbide, I have use 13-14" lathes and do most of my work under 1000 RPM with no issues. Depending on the insert geometry/coating/etc. many work well at lower SFM.

  8. #8
    Join Date
    Feb 2018
    Country
    UNITED STATES
    State/Province
    Florida
    Posts
    20
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    4

    Default

    Beauty of using a VFD is you can skip using backgear or changing belts.
    I do a lot of custom screw making with a carbide insert tool and a geometric die, so I use those features a lot.

  9. #9
    Join Date
    Jan 2005
    Location
    Duluth, MN
    Posts
    507
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    45

    Default

    Thank you all for your replies. As you can tell from my questions I have very little experience/knowledge of VFDs. I found an old unit at a surplus store and brought it home and connected the 230V/1PH input and the SB 13. The VFD was so old that the enclosure measured .8X2X3ft. and had several circuit boards plus many large capacitors and an equally large choke. It worked well for several years until it didn't. I think the choke shorted.

    I then made a RPC using a 3 HP motor-start and run caps-momentary contact switch. Worked great and was bullet proof. To mitigate the noise I used a rubber pad between motor and concrete floor. I actually hard wired the 3PH machines as I added them.

    You've scared me off VFDs. I'm going the 1PH motor pulley switch route. Unlike the presidential candidates my advanced age-75 yrs.-has greatly diminished my abilities.

    Even with the VFD I usually used the belts/gears to reduce machine speed because of the constant power. I also didn't like over speeding/stressing old machinery.

    Thanks all for sharing.
    Larry

  10. #10
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    27,310
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8516

    Default

    Quote Originally Posted by Larry on Lake Superior View Post
    To mitigate the noise I used a rubber pad between motor and concrete floor.
    LOL! The secret to a stealthy, quiet, no-annoyance RPC does indeed have to do with the feet.

    About 40 feet, straight line, several walls in between, from the shop to the carport, RPC adjacent the MEP-803a diesel.

    Same wire, one extra transfer switch, and I also have "true" 3-P off the Diesel if the mains are out, same panel and outlets at the shop end.

    "Wire exists", relays and indicator lamps as well, and they all work a treat!


  11. #11
    Join Date
    Jan 2005
    Location
    Duluth, MN
    Posts
    507
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    45

    Default

    Thermite-
    You are prepared! Boy Scout?

    I enjoy your posts as I am SLIGHTLY irascible as well. Luckily, due to my age, I experience few blows to my face.

    Keep on keeping on!

    Thanks,
    Larry

  12. #12
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    27,310
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8516

    Default

    Quote Originally Posted by Larry on Lake Superior View Post
    Thermite-
    You are prepared! Boy Scout?
    Not as polite as all that!

    2d generation Combat Engineer, thousand and more years of "farm boy", UK first, Virginia, 1730 onward.

    Reality is that whilst Dominion Virginia Power and all underground utilities last few miles serve Northern Virginia really reliably - just compare the Marxist side of the river (DC and Maryland) and weep.

    OUR small development was built STOOPID. Poor/no fault isolation nor monitoring gear.

    A hungry snake chases a rodent into a transformer, takes right about 3 HOURS of a whole bunch of DomVA krew walking the streets in pairs until the Mark One Human NOSE finds which one tripped the whole local grid!

    Or three days, weather is bad enough.

    Or seven days, but only the once in the 30+ years I've been here. That was an inland storm as set records for outages, cellphone towers and internet as well, far too much of the East.

    We have not only lost frozen goods, one time I was overseas and oblivious. By the time I got back, had to send the whole fridge/freezer off to the landfill, it was that bad.

    T'other reason is that with ages 68 to 90, we NEED air-con on 102+ F days. Timberline wood stove can't do that, but the 10 KVA gen set will haul either of those loads, plus all other cooking and laundry, so long as spaced-out sanely.

    Yah... keep grinnin' .. confuses the shit outta yer enemies!



Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •