2 phase Whiton Centering Lathe Machine - Page 2
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  1. #21
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    Quote Originally Posted by IrbyJones View Post
    Running 2 phase motors using a RPC was discussed in this thread:
    Single-phase to Two-phase and Three-phase

    I get a headache trying to follow it all, but it shows how to achieve it. And since you have a rotary convertor, Mike, maybe your brother can help you get that old motor running with help from that thread.

    Irby
    The short story is that with an RPC operating from the standard 240V single phase, you have a neutral on the incoming 240V. The voltage from the neutral to the generated leg of the RPC is at 90 deg to the incoming single phase, but is at a lower voltage. The idea expressed is to use a boost transformer to raise that to the 240V to get the 90 degree phase shifted voltage needed.

    That works as far as the phase shift, but may not work with a particular motor because it is effectively a "4 wire source".

    The. 2 phase came in 3 wire and 4 wire varieties, and I do not know which was more common or which your motor uses. The 4 wire motor has two independent windings. The 3 wire has a common lead that is connected to one wire of each winding.

    Motors using 3 wires would not be reversible, if they have 4 wires, they would be, and would work on either a 4 wire or 3 wire source

    The RPC-derived 2 phase needs a 4 wire motor, because the neutral is obviously not common with either leg of the 240V, and that voltage needs an independently connected winding... a 4 wire motor.

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  3. #22
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    2phase.jpg


    keep in mind that you will have to program the vfd for linear volts per hz with very little "boost" volts. because otherwise you saturate the transformers and short out the vfd. so you're not going to get full torque below perhaps 30hz because you won't be able to shove enough volts into the motor to get the current you need.


    buck boost transformers usually have a 16/32 or 12/24 secondary and a 120/240 primary. you need a 32:208 ratio which is similar to a 37:240v transformer.

    a 40 volt secondary, 240v primary transformer would be a good option for that transformer. due to voltage drop under load, a 48volt transformer would probably work as well.

  4. #23
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    Yes, it is a 4 wire motor.

    Thanks for the sketch!

    It looks like the Everglades to me, but, maybe my brother can figure it out.


    I have some friends out East and have asked them to watch for a 2 phase motor for me, to add on like northernsinger suggested.


    This one is 1 1/2 hp, so, I would guess I need one at least as big, if not twice the size, like is called out for a common converter.


    If anyone has an extra one laying around, I'm game for a road trip.

    Thanks

    Mike


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