50 HP rotary, "To pony or not to Pony ?" That........ - Page 2
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  1. #21
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    railroad ties.

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  3. #22
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    Quote Originally Posted by jim rozen View Post
    Basically just size this up by a factor of ten. 5 -> 50 and 0.125 -> 1-1/2 and then give it a try and see how it does.

    (you probably want to replace the 2x4s with 6x6 timbers...)

    I've always liked this picture and the simple solution to a problem. The OP is asking whether he should use a pony start for a 50 hp idler? LOL

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    The 30hp I built years ago started just fine with a 3/4 hp TEAO motor that was belted to it so that it would over speed the idler a bit. A timer would shut down the starter motor, let the idler coast down to near perfect synchronous speed, then a contactor would apply L1-L2 to the idler. The timer could be fine tuned to get the coast RPM just right, so no large inrush or crow baring to achieve synchronous speed. Worked great, simple. No one way clutch or "cam" required.

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    Say I was willing to trade in my 50 hp motor and get smaller motors. A 20hp then 10 hp and finally another 20 hp. Lets say I peddle them in that order. I only get a RPC cabinet for the 20 HP. I understand that I have to parallel them all together and utilize relays so that I can throw them on one after the other as needed ( might use timer relays and 3p contactors for that job). How do I make it so that I don't have too much run capacitance when only running the main idler alone and don't have too little run capacitance when running them all? Do I have one set of wires feeding all these motors and then another wire outputting the power with 30 HP worth of run capacitance in there?

  6. #25
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    That sounds like you're way over complicating things for the fun of it.

    Quote Originally Posted by madmachinst View Post
    Say I was willing to trade in my 50 hp motor and get smaller motors. A 20hp then 10 hp and finally another 20 hp.

  7. #26
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    I have a 30hp RPC and it pegs the power meter under startup, so I think that you are definitely smart to use a pony motor to spin it up.

    Air compressor motor's are designed for higher starting loads, so one would be a good choice for a pony motor.

    As far as disconnecting the pony motor, my question is why disconnect it physically? If you simply disconnect the power once the RPC is spun up, the pony motor can simply spin w/o power.

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    Quote Originally Posted by Newman109 View Post
    I've always liked this picture and the simple solution to a problem. The OP is asking whether he should use a pony start for a 50 hp idler? LOL
    Thank you. Best part of this setup is, the black motor is a 1/8 hp repulsion induction start motor that I inherited from my grandfather who was a dentist. It's made by Pelton and Crane, and came off an air compressor made by those folks. An air compressor, designed for dental offices. It's one of the few things I asked for when his house was cleared out, he had that in the basement of his house. A 1/8 hp motor from the '30s, used to start a 5 hp rotary converter, in my house, in the 21st century....

  9. #28
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    Quote Originally Posted by madmachinst View Post
    Say I was willing to trade in my 50 hp motor and get smaller motors. A 20hp then 10 hp and finally another 20 hp. Lets say I peddle them in that order. I only get a RPC cabinet for the 20 HP. I understand that I have to parallel them all together and utilize relays so that I can throw them on one after the other as needed ( might use timer relays and 3p contactors for that job). How do I make it so that I don't have too much run capacitance when only running the main idler alone and don't have too little run capacitance when running them all? Do I have one set of wires feeding all these motors and then another wire outputting the power with 30 HP worth of run capacitance in there?
    Each motor would need to have its own capacitors, they are only in use when that motor is energized. You can also go farther with that and balance each machine with its own caps. That might be overkill for most situations.

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  11. #29
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    no diagrams out there for something like this?

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    Quote Originally Posted by madmachinst View Post
    no diagrams out there for something like this?
    ............

    jbxplfp1u9p61.jpg

  13. #31
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    Quote Originally Posted by madmachinst View Post
    Say I was willing to trade in my 50 hp motor and get smaller motors. A 20hp then 10 hp and finally another 20 hp. Lets say I peddle them in that order. I only get a RPC cabinet for the 20 HP. I understand that I have to parallel them all together and utilize relays so that I can throw them on one after the other as needed ( might use timer relays and 3p contactors for that job)....
    Not needed. Run your single phase into 2 main lugs of a 3 phase distribution center (or breaker box, to this hick) and connect all your motors/equipment to separate breakers. Single phase can be picked off and extra motors for phase conversion can be connected and switched on and off using the breakers.

    ....How do I make it so that I don't have too much run capacitance when only running the main idler alone and don't have too little run capacitance when running them all?....
    Separate cap box for each idler on its own circuit.

    ...Do I have one set of wires feeding all these motors and then another wire outputting the power with 30 HP worth of run capacitance in there?
    That's too complicated. Keep it simple, each motor/cap combination on its own circuit with its own overcurrent protection. If you don't like using a breaker for a switch (some don't), then put a 3 pole disconnect between the breaker and its idler.


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