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  1. #1
    Shortrnd is offline Plastic
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    Default Need Help! Wiring from SPC to .... Magnetic Starter?

    I really need some help from you guys that know what you're doing.... apparently I don't.

    Please bare with me as I really don't know much about electricity. If you want to reply to me as though I'm a 4 year old just so I understand, then please feel free.

    I'm trying to wire my 10" Sheldon lathe and here's what I have going on.

    First off, here's my lathe.

    The lathe

    lathe again

    This is the box on the left side opened up. Magnetic starter?

    front

    terminals

    wiring diagram

    From my Phase-A-Matic Heavy Duty SPC (1-3 hp if that matters) I hooked up A to L1 and C to L2. With B unconnected I can hear something in this Square D box engage when I push the start button on the front of the lathe. I'm assuming that is a good sign. It disengages when I push the stop button.

    I then connected C to L3 and I get the same result. My problem is when I try to start the machine, the spindle rotates and tries to start, the light on the converter comes on, then the light shuts off before the motor gets to full speed and then tries to start it again. All of this happens continuously very fast.

    I have a feeling it's something simple but I just don't know what it is. I've tried to supply as much info as I can but if you need more then please ask. Thank you very much in advance.

    Martin

  2. #2
    minder is offline Stainless
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    Default

    It sounds like you have the contactor hooked up OK if you can hear and see it pick up.
    If it stays in the whole time that the motor tries to run and the P.C. drops out, It could be a problem with the motor, causing the P.C. to drop out due to overload?
    Has this motor ran since you got it, or is this an unknown?
    M.

  3. #3
    Modelman is offline Stainless
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    Martin,

    You have a 3 phase motor, so it is expecting to see all three phases of power. That's the reason you are using the phase converter. As it is, it sounds like the contactor is picking up, so the start circuit is wired correctly, but without 3 phase power, the motor won't start. The third lead from the phase converter needs to go to the third LINE terminal of the starter. I assume A, B, and C are the three outputs of the Phase-A-Matic SPC. If this is correct, try connecting B to L3.

    I have an additional concern with using a static phase converter. The voltage on the "manufactured" leg can be pretty unpredictable. Normally doesn't hurt the motor, but I have concerns about the coil. Therefore, I would make sure the "B" phase of the SPC is connected to L3, which keeps it out of the start circuit. If the motor runs the wrong direction, transpose any two of the motor leads on the T terminals of the starter, it doesn't matter which two.

    I notice that the starter is rated 50hz (cycles per second). I assume this is a British manufactured lathe, and the motor is 50hz also. Standard in North America is 60hz. So, your lathe will run, but 20% faster than was intended. Shouldn't hurt anything, but any speed tables will be off by 20%. The easy way to correct this, if it's a problem, is to replace the Phase-A-Matic with a VFD (Variable Frequency Drive) set to output 50hz.

    Dennis

  4. #4
    Shortrnd is offline Plastic
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    Minder,
    I know for a fact that the lathe works. I saw it running before I purchased it. It was connected directly to 3 phase 220v at it's last home.

    Also, I know the phase converter works. I hooked it up to my mill and it works fine. I kow there are a ton of variables to look at when working with static converters so this may or may not mean anything.

    Thanks for the response and help.

  5. #5
    Shortrnd is offline Plastic
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    Dennis,
    Ok I'm with you for the most part. I pretty much understand the phase concepts. The B contact on my converter is my manufactured leg..... if that's the correct terminology. I have that wired to L3.

    I've tried all of the other combinations of wiring A and C to the L1, L2, and L3 contacts with no luck. Having them connected to L1 and L2 is the only way I could get the starter to pick up. I'm assuming this is correct then?

    I have no clue about the manufacturer. If I have no luck I'll look into using a VFD.

    Thanks a ton. If there's anything else you can think of then please holler.

  6. #6
    peterh5322's Avatar
    peterh5322 is offline Diamond
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    An SPC can be wired to a magnetic motor starter, even a reversing magnetic motor starter.

    Each SPC has its own issues, but perhaps the best documentation on wiring an SPC to a magnetic motor starter is that which is for an H.A.S. static:

    http://www.capacitorconvertors.com/p...structions.pdf

    The internal schematic of the SPC is provided, too.

    This is for Steelman's patented (since expired, I believe) method of powering twelve-wire three-phase motors from single-phase, but the concept may be useful for nine-wire cases, too.

  7. #7
    Modelman is offline Stainless
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    Oh, then I misinterpreted what you said you've done in your original post. I don't know a lot about static phase converters, other than the prevailing opinion on this board is they are inherently evil devices. That being said, I thought they needed to be somewhat closely matched to the motor's electrical characteristics? The fact that the manufactured phase won't pick up the contactor seems to say something about this.

    From the operation you describe, it sounds like phase converter isn't happy with the load the motor is applying, and is dropping out the third phase, only to try to restart again. If I read what you wrote correctly, through all this the start coil stays energized? That would tend to support my guess that the phase converter keeps dropping the manufactured phase.

    I also do not see any sort of motor overload protection; the Square D device is only the power contactor. Motor starters also have an overload relay between the contactor and the motor, which usually also has a set of contacts in the start circuit to drop the coil out if the overload relay opens. If we assume that the lathe was wired correctly in its last home (not always a safe assumption) then there must be thermal overload protection somewhere else, such as built into the motor. It could be possible that a weak manufactured phase is causing this overload to see too much current between the two lines that run through the phase converter from the supply, isn't happy, and is opening under the starting load. Again, this points to a problem in the manufactured phase supplied by the phase converter.

    At this point I'm at the limit of my expertise, perhaps someone with more experience with the capacitor type phase converters will chime in. All I can suggest is that to get full HP out of the lathe, you really should be looking at a VFD.

    Dennis

  8. #8
    peterh5322's Avatar
    peterh5322 is offline Diamond
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    That Square D device is a NEMA Size 00 contactor, not a magnetic motor starter. It has no overloads.

  9. #9
    minder is offline Stainless
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    Just to eliminate any mis-wiring you may have done, you could disconnect the 3 ph right at the motor, tape them up separately, and power every thing up.
    The contactor should pick up and stay in, the P.C. stay on.
    At this point you could also measure the 3 phases out to the motor.
    If the P.P.C. still drops out, you have a problem, but you have virtually eliminated the motor itself.
    M.

  10. #10
    JunkyardJ's Avatar
    JunkyardJ is offline Titanium
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    Question Could he temoprarily drop the starter???

    I think the lathe is too much starting load for the static phase converter. This is somewhat common from what I understand with static phase converters and lathes. First, set the lathe to it's lowest speed, and see if it starts, that will take some load off the motor. Also, make sure the lead screw and power feed rod are disengaged just in case they're binding something. See if it starts like that. If not, I think it's time for a VFD, I'd ditch the static phase converter JUST for variable speed, but the VFD CAN start it if it does work right. The VFD will also give you full power output from the motor, where SPCs give you 66%.

    Before doing this next thing, GET CONFIRMATION. I dunno if you have to have a static phase converter on before you turn on the motor, but if not, you could try hooking the motor directly to the SPC. Then throw the breaker to turn it off and on (OBVIOUSLY you turn off the breaker BEFORE wiring). Make sure the contactor is disconnected from the circuit. there's a possibility it's screwing with the SPC. If this doesn't work, get rid of the SPC, and GO VFD!!! Some places (like wholesale tool) deny your warranty on the motor if it's used with a static phase converter. I put a Hitachi SJ200 on a friend's MASSIVE 16"x8' Hendey lathe, and he loves it!

  11. #11
    2Slow's Avatar
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    I think Junkyard J is 100% correct on this one. The lathe is presenting a load that is too great for the static phase converter to start. You could try increasing the size of the start cap, but you will have to make sure that the PR and all the rest of the components in the SPC are sized for the increased capacitence and resulting increase in current.

    If you have a 3 hp 3ph motor laying around you could build a crude RPC with your SPC and an idler. That would probably get the lathe going.

    -Joe

  12. #12
    Shortrnd is offline Plastic
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    Default

    Thanks for all of the replies, guys. I've tried all of the suggestions posted and still no luck. I wasn't in the lowest speed but I was at least smart enough to disengage the power feed and lead screw....... still no luck.

    I've decided to go the route suggested by 2slow. I'm going to use the SPC to make a RPC and see if that works. If not then I'll go with the VFD as suggested.

    Thanks again and I'll be sure to post back here to let you guys know if I'm in business.

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