Have 15hp Baldor, want to make 3 phase converter - Page 2
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  1. #21
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    Buce,

    I am not concerned about pressing the start button once the idler is running. IF a person does this once he will remember not to do it again. There may be a better way but I have not thought of it. It may be possible to use a push button switch with two N.O. switches. The ones I have are one N.O. and one N.C. I used the normally closed switch because I need a little time delay after pushing START so the Control Relay has time to engergize and open the normally closed contacts to lock out M1 (idler motor start conctactor). Without the normally closed contacts in the Start button I would need a time delay relay or a solid state time delay. I you do use a time delay then you only need the start button to have one set of normally open contacts.

    I have not wired the circuit but I am sure the CR1 (control relay) will need to be 120 volt as the pony connected for 240 volt has two run windings in series and with the start winding connected at the center point of these two. The start winding is a 120 volt winding and I Have the control relay connected in parallel with the start winding. There are capacitor start designs with 240 volt start winding but the most common type is the 120 volt start winding and it is the type motor that I have.

    As to heater elements on the generated phase: I do not think it is needed but you will need a blank to replace the missing heater so it is just as easy to use a heater element. I suppose you could get a 2 pole overload relay but you really need the 3 pole so you have enough lugs for connecting all the wires. I once had a drawing showing a blank on this generated phase and everybody i gave it to asked why I did not use a heater--can't win in this game./

    PR is a potential relay and I use it to detect when the idler is converting properly. I thought about the normally closed contact on M1 but decided the potential relay would be some better. It provides a little time delay before shuting down the pony motor. It would be worth trying with the N.C. contact though.

    Finally someone has looked at the circuit.

  2. #22
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    See if this address the push START twice problem. It may very well solve the problem.
    Attached Thumbnails Attached Thumbnails pony-motor-rpc-v2.jpg  

  3. #23
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    Buce,

    Here is larger diagram of the connections in a single phase dual voltage motor with single voltage start windings and capacitor start. The start winding always has 120 volts across it.
    I hope this explains why I show a 120 volt coil in the control relay. Maybe some motor gurus will chime in to correct or confirm this hookup.
    Attached Thumbnails Attached Thumbnails single-phase-motor.jpg  

  4. #24
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    I'm back, been kept busy lately. I just barely looked at the new diagram, will look closely soon. That motor diagram helps.

    More soon.

    Bruce

  5. #25
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    ToolNut,

    That blue connection to an M1 switch fixes the turn off of M1 on an accidental push of the start button when the system is running. But I知 thinking we can eliminate the need for the normally closed contacts of the start button. I知 working on a diagram where CR1 has one NO and one NC switch... most relays do.

    Bruce

  6. #26
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    Buce,

    Would like to see your diagram when you have it. It may give me some new ideas.

    The N.O and N.C contacts on the start switch are no problem as a standard Allen Bradley contact block contains both. I suspect you can do it with the relay also.

  7. #27
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    ToolNut,

    I'll make it presentable and snap a picture of it today.
    We're still looking for:
    Pony motor
    Heater block for 15 hp
    Capacitors

    We have every thing else.

    What kind of collection of sizes of capacitors do you think I might need to tune this thing according to the Fitch Williams scheme?

    Bruce

  8. #28
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    Buce,

    Here is a balancing table from a 10 hp idler RPC I built last year. Since your idler is a high effieciency motor I would expect the capacitor values to be somewhere between these and 150% of these. A high efficiency motor usually requieres less capacitance but I have not used enough of them to know how to estimate the values.

    I get capacitors used from. www.surpluscenter.com. I usually use 40 mfd or 50 mfds and you may need a couple of 20 mfds for tuning. the Cpf will require some 20s and a 10.

    Send me a PM with an email address and I can send the drawings in a better format if you need them.

    The file was too large to upload. Here are the totals for the 10 Hp
    Cp=160
    Cs= 120
    Cpf = 20

  9. #29
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    Tool Nut,
    We found a 2hp Baldor single phase for nothing. Right under our noses. We will swap one off one of my sons machine for a three-phase that he couldn't previously run. Sorry about disappearing again but I'm being kept busy by putting food on the table. Our objective now is to have every last thing to assemble this converter on hand by the last week in Feb and then at the first opportunity... do it. I still need to post that diagram with multiple contacts on the pony motor relay. Thanks for that lead on capacitors, I値l order some.
    Bruce

  10. #30
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    Default The rest of the story?

    I have been reading, collecting, etc. for quite some while to build an RPC similar to what Bruce is doing and toolnut always has great ideas.

    So, I wanted to call bruce's hand and ask "Where's Them Pics and schematics".. After all you did promise to post both, but then you may not be finished yet.

    Anywho, hate bump an old thread but this one was going well and I think many would appreciate the rest of the story if there is one..

    Thanks for all the great info that is exchanged here.
    BillyD..

  11. #31
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    Default Back to work on this project

    As anyone can tell this project got stalled but I知 back to it now. I have the mechanical stuff darn near done. The belt guard is done and the paint is drying.



    The electrical gear is spread over my worktable and as soon as the paint inside the electrical box dries it will start going in.

    I知 having a bit of a problem selecting wire size. Our budget is low. I have some #6 THN and some #8 THN. I知 thinking that since the ampacity of the #8 is 45 amps and I need 90 amps that I can parallel two runs of #8 instead of laying out almost $2/ft for #4 or larger. An alternative would be to use the #6 and use a 70 amp breaker but it seems a shame to limit the machine.

    I would appreciate any opinions on paralleling conductors.

    Also I'm thinking that the ground wire from the supply panel only needs to be #8. Any opinions on that?

  12. #32
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    Default Wire Size

    I'm trying to understand the necessary wire sizes at various places in the circuit for a 15hp RPC with a 90-amp supply breaker:

    1) Supply panel to RPC (Two parallel #8痴 for L1 and two more for L2???)
    2) From heater coils to idler and from generated leg back to RPC panel (#6?)
    3) From each 3 phase leg to each of the three capacitor banks (#8?)
    4) From each capacitor to each capacitor bank lead (#10?)
    5) Ground wire from supply panel (#8?)
    6) From idler contactor to a bank of 3-phase circuit brakers each of which will supply a particular machine. (#6?)

    Since the connected 3-phase load draws one third of its power directly from the wires of the supply panel I知 thinking I can use #6 wire between the heater coils and the idler and from the generated leg at the idler back to RPC panel.

    How far off am I in my assumptions?

  13. #33
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    That where you been, building that neat carriage for your RPC.
    Looks great and I love the floating pony motor.

    Hope Toolnut is ok, I would like to see his 2cents on a few of those questions myself.

    Happy Thanksgiving.
    BillyD..

  14. #34
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    BillyD,

    I am doing fine, just recovering from building my pony motor start RPC which I demonstrated at this years "ArnFest". This is the annual meeting of the Old Wood Working Machines group. I had to change from the diagram I posted here and used a time delay relay to switch off the pony motor. The design worked well and I am satisfied with it. I had to use a 7-1/2 hp idler for the demo as there was not sufficient power available to operate a 15 hp RPC. I now have a new old stock 20 hp, 3450 rpm idler to install in the RPC when I get a chance. i need to do the same as Buce and build a nice steel base.
    Send me a Private Message and include your email address if you would like a copy of the drawing. I am not sure it is small enough to attach to a note. The drawing is not a complete plan but does show all the components and how they are connected.

    I have two more capacitor start, 7-1/2 hp, RPCs under construction now. I plan to make photos of the second one and hope to rework my construction instructions, then I will post the plans, photos and instructions. I now get so many requests I can not keep up and I have ceased making changes to the plans.

  15. #35
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    Thanks, and sorry to hear they were a little short on power.
    Would love to see whatever you have when you have time to send, will pm.

    I now get so many requests I can not keep up and I have ceased making changes to the plans.
    That's no wonder as in my short time on the forum I have enjoyed many of your tutorials.

    I saw mention of the "ArnFest" event and wasn't real sure what it was. So of course I googled it, and found arnfest.org. Now I'm curious if there is any similar event in the Texas area, being in Houston myself.

    Looking forward to more of your expertise.
    Thanks
    BillyD..

  16. #36
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    I致e gotten a lot of wiring done and am in the process of verifying it. I値l post pictures and a wiring diagram when it is actually operational a week or two. One of the used switches seems to have problems and I may have to await delivery of a new one.

    I致e learned a lot in the process of building this thing. Like why choose to build a pony motor design. My reason is that it will be used on the very end of a rural road with quite a few homes on it. I think the pony motor start on the 15 hp idler will be the neighborliest solution, but maybe not by much over some other designs.

    If I were to start afresh I think I would use a small 3-phase motor (not belted to the idler) with a capacitor start and wire it up to start the 15 hp idler. That way the starting motor would be left running as a dual idler system and it would add capacity. With the belted single phase pony motor design the pony motor becomes a drag on the system after startup is achieved.

  17. #37
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    I致e made progress. The unit is up and running and ready to add the capacitors. It will run our 3-phase motors as it is but we will add the capacitors next weekend.

    I have a wiring diagram in pencil but it is not photographing well. I値l work on that and post a better copy soon.



    Here is a picture of the control panel just after checking out the control circuitry.\



    If the pony blows its own dedicated 25-amp circuit breaker the control panel shuts down.

    If either the pony or the idler heater elements are tripped out the control circuitry is disabled and the control panel is shut down.

    If the idler contactor is closed (and the idler is presumed running) the start push button is disabled and thus will not start the pony.

  18. #38
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    That's looking good Buce.
    On the pony motor drag and your sweet carriage, I have seen some awful inexpensive solenoids @ Surplus etc. that you could sneak in so when starting it would tighten your belt and afterward relax to reduce drag.. just a thought.

    Keep up the good work and let see the finals when you get there, with some cap values..

    BillyD..


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