Wiring home shop for 3-phase power. Would love all the input I could get - Page 2
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  1. #21
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    For the Hardinge I would build a rotary phase converter, see appropriate section of forum. I did this with my Hardinge HLV-H which has a number of small 3 phase motors. Used a cheap 2hp 208V 3 phase motor, single phase motor starter, starting cap and time delay relay. Hit start button and TD relay drops out starting cap after one second. Using 208V equipment on 240V input has not caused me any issues.

    For 600V, on my Bridgeport I used a 3KVA step up transformer, 240V in and 600V out. These are commonly used as step down transformers for lighting applications in shops so many electricians have used ones around cheap. Fed resulting 600V single phase into a VFD and achieved very good results.

    I have been running the above set-up for over 10 years. Only issue is the old VFD failed due to condensation as the boards and components were not properly coated. Fixed it about 6 times, last time multiple little problems combined to make it junk. Newer one installed and all is good.

  2. #22
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    Quote Originally Posted by DIYShopTools View Post
    I guess it's about time to start really researching how to build a rotary phase converter. And I've got so many single phase motors that I've been able to pickup for next to nothing - or in some cases, literally nothing, that I'll be happy to have found a use for one as the starter motor for the phase converter
    Quote Originally Posted by neilho View Post
    Using the rope-around-the-shaft method would get you started making chips. (Remembering to wind the rope around the shaft the same way every time is the most difficult thing about that setup.)
    Certainly a rope-start is the easiest no-cost way to get started. Assuming the motor is wired for 240 3-phase, hook up two of the phases to your 240v leads. Hook up all three of the phases to the 3-phase input on the lathe. Pull rope to spin up the idler (RPC motor), and away you go.

    Setting up a pony motor is a bit more trouble, as you will need some sort of mechanism to engage and disengage it. May be as simple as an old v-belt, a hinged flap, and a wedge to stick under the flap to raise it enough to disengage the belt.

    BUT - for both of these, you are probably going to want to have some kind of switch, so that the idler isn't sitting there buzzing while you wind up your rope. You could "switch" it by just plugging it in, but you've got to hold onto the rope at the same time. For the pony motor approach, of course you need a way to switch on both the idler AND the pony motor, and then be able to turn the pony motor off. And you'll need an appropriate plug for the single phase side, and an appropriate socket for the 3-phase side.

    By the time you are wiring in a switch and a plug and an outlet, you might as go ahead and set up a simple push-button start system -- really is surprisingly easy. You can do this without going all the way to balancing caps, phase monitor, time delay, or so on, and if you know someone in the HVAC business, you can do it on the cheap - basically just the cost of the start/stop buttons to add to the cost of the single-phase plug and 3-phase outlet. Get contactors, 24v control transformer, and capacitors (start and run) from the HVAC scrap bin.

    There are multitudes of plans out there on the internet, and they can help especially with choosing a start cap size (and run caps for balancing, if you want to do that). But some of the plans are a bit over the top, and some are perhaps too simple to be completely safe.

    FWIW, here's what I did. I have a 24v transformer that is live whenever the 240v line is connected. The 24v signal goes to a normally open start switch, which feeds the 24v to switch the first contactor. This contactor uses one pole to forward the 24v to the second contactor, but it also uses the second pole to switch the start capacitor into the motor circuit. The second contactor is a 3-pole; two poles switch the 240v, while the third pole switches the 24v control through the normally closed stop switch and back to itself, so that once energized, contactor 2 will remain energized ("latched") unless / until the stop switch is pressed.

    I didn't bother with any sort of timer - I just press the start switch for half a second or so, and it switches on the 240 power to the motor while also adding the run cap into the circuit. The 3-phase idler motor kicks on within a half second or so. When I release the start switch, the 240 power to the motor continues, but the start cap is out of the circuit; the idler motor continues to run, generating the 3rd phase. When I press the stop switch, the system immediately powers down, and will not power back up until the start switch is pressed again.

    I had originally planned to use run capacitors to "tune" the legs of the resulting 3-phase ... but I found that they were already so close that it was not worth the effort.

    It all sounds far more complicated than it really is - or at least, it did to me when I read through the various plans. But when I actually built my RPC, it was, as I said before, incredibly easy.

  3. #23
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    Quote Originally Posted by awake View Post
    It all sounds far more complicated than it really is - or at least, it did to me when I read through the various plans. But when I actually built my RPC, it was, as I said before, incredibly easy.
    "It all"... also turns into the DAMNDEST waste of time.. and money. And we perpetuate that, "right here on PM".

    Weigh this, oh ye who have not YET "had the RPC experience".

    - The "pilot" or "idler" is an ignorant 3-P induction motor. One of mankind's most simple and durabler of devices ever made. Of any kind. Average roof on a residence doesn't last as long nor work as well. Nor a motor vehicle. Low risk, IOW.

    - Starter/controls? Hem's sake.. it has all been DONE before. Multiple tens of thousands of times.

    - EITHER .."DIY" from a copy of any of the many "designs" already in PM "stickies" OR all over the internet, dozens of other sources. They are not all that different.

    - ELSE JF buy one. Many of us spend more on groceries for a single month.

    -- the groceries soon turn to s**t - as they are MEANT to do.

    -- 240-plus more grocery bills - 20-plus years out, the RPC just keeps on turning, as it is "meant to do".

    Why do we make a problem out of a solution, not "once in a while", but every time the question comes up, do that all over again, time after time, after time for decade after decade?

    Just make a decision:

    * Buy it, 100% ready to go.

    * Build it 100% "from scratch"

    * Buy the control and mate to your own idler motor.

    "Decisions, decisions, decisions".

    If there were THREE rolls of bum-fodder in a toilet stall?

    Some folk might die of old age, thirst, or starvation, sitting on the "throne",

    ....unable to select ....."a way... back ward".

    If you think THIS is hard? How do you ever expect to be able to eat a live snake, shag a Kodiak bear, face a firing squad, arm-wrestle an Octopus, or even just vote in the next election without guilt over whatever happens afterwards?


  4. #24
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    I started out using a VFD on my old J-head B'Port. I didn't like it; too slow starting and stopping. I do a lot of power tapping, and rely on instant reverse. Set to the fastest setting, the VFD seemed very slow to reverse. Program it any faster, and you risk letting the magic smoke out. When I bought it, I didn't realize that it had to be set to the particular motor you were using. Fine for one machine; not so much for my 3 ph surface grinder, lathe , etc.

    I just finished putting together a 10 hp RPC. I bought the idler at auction for $25, and went ahead and bought a nice control panel for $300. Works GREAT; feels just like regular old 3 ph. I can run multiple machines, or one machine, whatever. To test the motor, I spun it up with a cordless drill, and jury-rigged the wiring to my mill. It worked fine without a control panel, but I prefer having the start capability and more balanced power. I couldn't spin the idler up enough with a rope. I screwed a bolt into the end of the spindle, chucked a 1/4" extension and socket into my cordless drill, and spooled it up. If I were on a really tight budget, I guess I could have gotten by with just that. I bought an American Rotary AD-10 panel, and added a 30A breaker to the DIN rail inside, rather than buying and wiring up an entire 3 ph panel.

    I'm going to try to sell the VFD. If no one buys it, I might use it on the surface grinder for the soft start, and ability to change the RPM.

  5. #25
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    Quote Originally Posted by MushCreek View Post
    I'm going to try to sell the VFD. If no one buys it, I might use it on the surface grinder for the soft start, and ability to change the RPM.
    IF you do that.. AND your SG is direct-drive.. motor hard to find a replacement for .. suggest you run the VFD output through a full-isolation transformer.

    Generally easier to find - used-but-good, and no more expensive than a sine-wave filter.

    Either one will protect a motor not made for VFD from switching artifacts and imperfect wave-forms so it lives longer.

    Page Two:

    Braking/reversing. A 4Q DC Drive & DC motor is your go-to. The GRID is its braking resistor.

    Better yet? A GOOD mechanical tapping head. MUCH "better yet", actually.
    It's what they are MADE for, after all!


  6. #26
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    I'd get a tapping head if I were doing production work. Too much trouble to swap out and set up for the work I do, which is spot/drill/tap, changing the bits in a keyless chuck. I'm retired now, so it's just hobby work. Still, in 45 years in the trade, I've never seen a B'Port motor quit, even running production.

    Interesting to know about the SG motor. Will a RPC hurt it? I had my shop at home years ago, and ran a Harig 612 on a static PC. It ran very hot, so I tried to use it only for brief periods. I have another Harig now, and let the spindle run for an hour on my new RPC set-up. It didn't even get warm, so I assume it's happy. Again, I won't use the SG very much; I'm not even sure what I'll do with it besides sharpening end mills in a fixture.


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