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  • Question on Chinese 10HP VFD...

    I'm sure this has been asked before- heck I've asked it before - but I'm having a hard time coming of with a definitive, solid answer.

    I'm in need of a VFD for my 10HP Springfield lathe. The one "proper" VFD I've found that can definitely take single phase and give me 10HP worth of 3-phase, costs $1,200.

    However, there's piles of Chinese VFDs on eBay that say they're good for 10HP/34 amp, for far less ($250-$300 plus shipping.) I'm given to understand, though, that generally speaking, a "10 HP" VFD is only rated for that 10HP on 3-phase. For single phase it'd technically only be rated for 5HP.

    Or, if it were rated for 10HP on single, it'd be good for 20HP on 3-phase. The problem is, none of the eBay ads say anything about that. They all simply say "use 1 or 3 phase as you like".

    So the $64,000 question: CAN the eBay/Huanyang VFDs actually run a 10HP motor on single-phase 220V input? (Example given, assuming the link works.)

    Doc.
    Doc's Machine. (Probably not what you expect.)

  • #2
    I only read that you can use 1 phase in the ad, but you should get hold of the manual to see more details on the specific model. The schematic is generic for the entire line-up so you can't tell anything from that.

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    • #3
      From the DC bus on, the VFD couldn't care less about the incomming power. As long as the DC bus voltage is maintained, then full output power is available.

      For operation on single phase, two things have to be considered. The current handling of the input bridge rectifier and the size and ripple current rating of the DC bus capacitors.


      For a three phase supply, the current on each conductor is Power/Voltage/SQRT 3.
      For single phase it's Power/Voltage.

      SQRT 3 = 1.732, so the current when supplied with single phase is nearly double. Remember that de-rate by 50% guideline?
      That assumes though, that the rectifer hasn't just been sized to handle the single phase current anyway. Sometimes the higher rated device doesn't even cost much extra.

      With three phase input, at no time does the output vlltage from the bridge rectifier drop to zero, but it does of course do so on single phase. The DC bus capacitors need to be sized to smooth the ripple and handle the higher ripple currents.

      Semiconductors and capacitors have improved a lot since the 1990's when VFDs started to become popular and they've generally become a lot cheaper for a given performance, so putting in a bigger input rectifier and a larger capacitor bank doesn't cost that much, but does open a whole extra market, where converting single phase to three phase is at least as important as the variable speed functionality.

      From what I've seen, the Huanyang VFDs do have a high enough rated input rectifier and capacitors that can handle the ripple current. The life of those capacitors in terms of 'hours under load' may be questionable, but those hours tend to be much lower in a home or job shop compared to a preduction environment.
      Paul Compton
      www.morini-mania.co.uk
      http://www.youtube.com/user/EVguru

      Comment


      • #4
        Don't buy one from eBay. Try one of these from an Amazon seller:

        https://www.amazon.com/Mophorn-Inver.../dp/B01M7PR9L6

        If it works, then great you're all set now. If it doesn't make all of your dreams come true you can return it for free through Amazon's no hassle return policy.

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        • #5
          I have two of the Ching-Chang VFDs for my mill. (One for the mill motor and one for the table feed motor.) Both work well in use but the mill VFD used to throw Error-02 sometimes on start or stop. Running the Auto-Tune for the motor seems to have alleviated that. I have both VFD control panels (remotes) mounted on a single panel like a DRO setup. They connect to the VFD chassis via standard Cat-5 cables. My only complaint is the LED displays are so dim they are hard to read unless shaded. That and the rheostat is very sensitive when adjusting Hz. It's hard to hit 60.0 so I'm typically running at 59.7 or 60.3Hz. I may change the display to two decimals and see if that helps. If I can see it.

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          • #6
            Originally posted by CCWKen View Post
            ... It's hard to hit 60.0 so I'm typically running at 59.7 or 60.3Hz. I may change the display to two decimals and see if that helps. If I can see it.
            That's within 0.5%, is it really that critical?
            Location: Long Island, N.Y.

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            • #7
              Probably not. I mostly look at the spindle RPM anyway. I've run the mill motor from 30 to 120Hz. The table feed manual gear box starts chattering and skipping above about 90Hz. It needs a few new gears and bearings but runs smooth at ~60Hz.

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              • #8
                Originally posted by CCWKen View Post
                Probably not. I mostly look at the spindle RPM anyway. I've run the mill motor from 30 to 120Hz. The table feed manual gear box starts chattering and skipping above about 90Hz. It needs a few new gears and bearings but runs smooth at ~60Hz.
                If the VFD is one of those that goes to 400Hz, you can reduce the sensitivity of the rheostat by adding a resistor in series with the terminal at the
                clockwise end. If the rheostat is 10K, then adding 20K should reduce the upper range to 1/3 or about 130Hz.
                Location: Long Island, N.Y.

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                • #9
                  Until a few years ago the Spedestar PolySpede was the only single phase to 3 phase I knew of that was rated and sold for full rated power with single phase in for larger size motors. I am sure there are others, but that one was designed and marketed for it.

                  However bear this in mind. How often will you actually be turning something that puts a 10HP load on the motor? If the answer is never then just program a slow easy start and slow down on your VFD and use a smaller one or use the Chinese 10HP. Calculate all your cutting loads at what your VFD can handle and you will still be able to throw rock sized chips. If I was buying one I'd tend towards full capacity, but if I had a VFD on hand I'd probably just run what I had and see how it worked out. I did that several years ago with my KMB1 (has a 5hp spindle motor) with the plan to get a 5hp SpedeStar. Well, many years later I am still running that 3.7kw (derate by 30-40% on single phase) Mitsubishi I had on hand. It does the jobs I need it to do.

                  I just noticed that Drives Warehouse no longer seems to have the PolySpede VFDs. I wonder if they are out of business or something else. All the listings say call for substitution. The PC1-100 was last listed by them at $1099
                  Last edited by Bob La Londe; 10-31-2017, 11:21 AM.
                  *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                  Comment


                  • #10
                    I needed a 2hp VFD for my mill as it had a two hp three phase motor and to replace it with a single phase would be expensive. I did a lot of research on Chinese VFD'S and decided to buy one made in US. I ended up buying one made by Leeson. Took a bit of reading to get it commissioned but I've never looked back, works great. Probably paid twice as much as an off shore but I hope it is better quality.

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                    • #11
                      Doc,

                      I installed a Speedstar VFD on a large bore lathe for a shop near me about 7 years ago. I spec'd out the job and as I recall the Speedstar was a 15 hp 3 phase unit being feed by 240 volt single phase so it was de-rated to 7.5 hp 3 phase. I have to warn you that it wasn't cheap. The VFD was $1200 back then but the real shocker was the cost of the input contactor. Speedstar recommends (at least they did 7 years ago) an input contactor to disconnect the incoming power in case of a fault in the VFD. This machine is used daily and the VFD has worked perfectly since day one. So I recommend the Speedstar. The manual is pretty good and Drives Warehouse was okay to work with.

                      I still have the electrical design if you need a jump start

                      Comment


                      • #12
                        See, this is what I was afraid of. The answer so far basically appears to be "buy it and find out for yourself".


                        Originally posted by Bob La Londe View Post
                        Until a few years ago the Spedestar PolySpede was the only single phase to 3 phase I knew of that was rated and sold for full rated power with single phase in for larger size motors. I am sure there are others, but that one was designed and marketed for it.
                        -And that's the one I'd been looking at. At the time, they had one non-UL-listed 10HP (on single phase) for $1,100, or a 20HP (on 3-phase that could take single) for $1,200. That was the only one I could find that definitively said yes, you can feed it 220V single phase and get 10HP 3-phase back out.

                        The cost was a bit daunting, so I haven't picked one up yet.

                        However bear this in mind. How often will you actually be turning something that puts a 10HP load on the motor?
                        -Most likely never. In fact I toyed with the idea of swapping in a 5HP, to make both the cost of a VFD and the daily operating costs lower. (And I still might.) The main thing that stopped me was the fact I'd likely have to make a new drive pulley to fit the smaller shaft- an 8-groove taper-lock monster that I'm not looking forward to having to recreate.

                        However, the current plan is actually that I'll likely sell this monster once it's back up to 100% again. It's a neat machine, but it's just too big both for my small shop and my day-to-day needs. I really need to shift it out of the way and bring in something CNC.

                        Therefore, I want to have this thing at more or less full capacity, so that any potential buyer (and it's big enough that likely means an industrial user) has that power available if they need it. I currently have it on a static converter, which works, but I want the soft-start of the VFD, plus the added variable speed option.

                        I just noticed that Drives Warehouse no longer seems to have the PolySpede VFDs.
                        -I've been watching them for a couple of years- they periodically go out of stock. But it's still listed, and able to be added to a "wish list", so presumably it'll be back in stock at some point.

                        And I'd love to pick one up, and be assured both that it'd do the job and is likely to last longer than a Chinese example, but my budget is too tight for that right now.

                        It's also too tight to throw $300 at an eBay drive in the hopes it'll work.

                        Doc.
                        Doc's Machine. (Probably not what you expect.)

                        Comment


                        • #13
                          Just buy one from Amazon. They have the absolute best customer service. If it doesn't work to your satisfaction, they will pay for return shipping and all your out is the time it takes to test it and put it back into the box if it doesn't work. You'll still have to do the same with any other unit -- top of the line or not, as they might not work either for whatever reason.

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                          • #14
                            Doc:

                            Many of the chinese drives seem to heavily depend on the source.

                            There are legitimate sources, and most of the drives sold through them work, even ones made in ways I would not accept (older Huanyang, etc).

                            There also seem to be bogus sources that have bought their drives out the side door of the factory, possibly stolen from the production line reject area. Those are the ones we all say may fail right away.

                            Problem is that you don't know which you bought from, until you find out it works or fails. Looks like some of the bogus sources may have raised prices so as to look more legit (and make more money).
                            CNC machines only go through the motions

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                            • #15
                              If it is a taperlock pulley, then you would need only make/acquire a different hub to use the current pulley.
                              North Central Arkansas

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