Wiring up a 460V 10ee
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  1. #1
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    I recently purchased a 1986 10ee which has the solid state control. The machine worked fine on 460v utility power but when hooking it up to my phase converter at home I have control problems. The lathe will not go over 1900 rpm and it trips the the control on the lathe when reversing rotation at any speed over 500 RPM. It will also trip if I reduce or increase the speed to fast on the control. The problem is worse if a chuck is attached to the spindle. When it trips the LED on the lathe which indicates improper phase hook up is lit. I have a 7 HP rotary converter that I have used for many other larger machines then the 10 ee. The only thing different is that I have attached a 3 phase setup transformer to the lathe to get the voltage up. I have checked line voltages at the machine. Across two of the legs I get 454 volts and across one of the legs I get 500 volts. A salesman selling phase converters thinks that I need to use a CNC quality converter and put a single phase step up transformer in front of the converter instead of using a three phase set up transformer after the converter. He also thinks that I might need a double converter to counter act the regenerative power effects created from the lathe when changing speeds. Any help of information would be appreciated.

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    You are suffering from voltage drop under load. You need a bigger phase convertor and higher amp circuit. Remember that stepping up the voltage requires double the amps and the phase convertor just worsens the situation as the third manufactured or wild leg has higher voltage that drops under load.
    If not sure, measure the voltage under load at 1800 rpm's, I doubt it'll be 440v.
    Steve

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    Good point I will check the voltages tonight. However I have used this converter for several years and I know what it sounds like when a hard load hits it. It just does not seem like thats what is happening. Maybe the lathe control circuit is just very touchy on the voltage.

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    I would expect that the additional transformer is giving you a couple of things - it's first dividing the available load from the phase convertor by 2 (the step-up value) and modifying the inductive load to the rotary phase convertor.

    My thought would be to get a 460V motor and run it as the phase converter *after* the step-up transformer. If you used a 7HP motor after the transformer that would be the equivalent of a 14HP before, and it'd let the converter motor handle the sudden changes in load without the inductive load of the transformer.

    I always wondered if the transformer after the converter would cause problems, I suspect that we now know.

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    It is usually best to step the voltage UP to 480 (from 240) and then convert to three-phase.

    The losses at 480 are lower than at 240. Plus, a single-phase 240:480 transformer costs less than a three-phase transformer.

    Figure on 1 KVA per HP.

    For my 3 HP WiaD 10EE (Reliance motor), I've selected a 7.5 KVA transformer, as I have the option (and the luxury) of installing an on-hand GE 5 HP motor, which came out of a 10EE which had been converted to VFD.

    FWIW, a "CNC Quality" converter is one which will maintain a phase B (i.e., "manufactured" phase) voltage of +/- 10 percent or better, under all load conditions. And, +/- 5 percent would be ideal. Such a converter usually must be both oversized and finely tuned.

    Remember: the capacitance required at 480 is one fourth the capacitance required at 240; however the minimum capacitor rated voltage goes from 370 volts to 740 in the process.

  6. #6
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    Can I use the 3 phase transformer that I already have and put it in front on the converter using only two of the legs on the transformer? I also noticed that when I check the wild leg to ground the voltage is 200 volts and not 120 volts like the other two legs. When checking the legs to each other the voltage runs with in 10%.

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    Each leg, other than the "high leg", should be 120 volts line-to-neutral, for a 120/240 system.

    The high leg should be 208 volts, so 200 isn't that bad, only about 4 percent low.

    However, you can improve that to nominal by adding caps.

    Should you transform 240 three-phase to 480, using your three-phase transformer, you will be creating a "separately derived" system.

    Be sure to properly ground that system.

    In most cases, you will be forced to "corner ground" the 480.

  8. #8
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    I'm not sure this will help as I have a 1962 tube machine. I would take a close look at your wiring diagram. My '62 is a 460v tube drive machine which is considered to be 3-phase. When I reviewed the wiring diagram in my initial setup stage I found the only need for three phase in the machine was a third leg available/used for a coolant pump. Since a pump was not an added option on my lathe I decided there was no need at all for three phase. I set-up using normal household 220v single phase into a 460v single phase stepup transformer and everything has worked fine for 7 years. I would have changed the lathe to run on 220 single phase except two of the transformers in the tube circuit were wired for 460v only and could not be re-tapped for 220v. I saved several hundred dollars by buying the stepup transformer rather than replacing the two filament transformers. In any event, the bottom line is: check your wiring diagram and you may find you don't really need three phase as all you need to do is control a D.C. drive motor. I'm no motor or voltage expert but I'm not sure there is any such thing as a three phase D.C. motor. Perhaps the better informed out there can help in that regard.

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    My 1956 10EE was also made without a coolant pump.

    In this specific case, phase B is indeed not connected within the machine (although the wiring for same is there).

    And, in this case, there is no reason NOT to utilize a 240:480 single-phase transformer to power you coolant pumpless 10EE.

    Should you later add a coolant pump, you can still satisfactorily power your 10EE by adding a small induction phase converter, sufficient to supply the phase B load, which is about 1/4 HP.

    A 1/2 HP 208-240/480 volt three-phase motor would certainly be sufficient to supply the required phase B load.

    A 2 to 4 microfarad, 740 volt rated oil-filled (i.e., motor run) cap from either phase A *or* phase C to phase B should make that 1/2 HP motor into a self-starting induction phase converter.

    (Two 4 to 8 microfarad, 340 volt rated caps in series would also accomplish the same result).

  10. #10
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    Thanks for everyones help. My 10EE needs 3 phase to work correctly. I was able to rewire the two three phase and one single phase transformers for 230 volt operation. The lathe now works great.


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