20hp RPC Pony start setup questions
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    Default 20hp RPC Pony start setup questions

    20hp Leeson idler
    FLA = 48a @230v
    1765rpm
    This is a 12 lead motor with 3 sets of 4 leads wired together for the 3 legs, (unlike many 9 lead motors)
    Motor also is inverter duty rated (label states "IRIS Inverter Rated Insulation System)

    I am very limited in electrical knowledge, so bear with me here, but upon googling about 12 lead motors, I am *THINKING* I may have what is called something like a "WYE-START/DELTA-RUN? motor, which can be setup for soft starting or something to that affect? Maybe you guys will know?

    Anyhow, my questions are very basic, and as follows:

    1. What size pony motor should I put on this 300lb monster 20hp idler? Is 1/2hp too small? Should I go with 3/4hp or even 1hp?

    2. I understand fully that either a 1725rpm OR a 3450rpm pony motor can be used, (with proper sizing of the pulley/sheaves) however, upon browsing Mcmaster Carr and ebay for 1.625" bored pulleys for the 20hp idler, I quickly noticed most pulleys are like 6"-7" in diameter. Nothing smaller.
    So this leaves me wondering if I should use a 1725rpm pony motor (same speed as my idler) and try to find a big pulley to match the idler pulley, OR if it would be easier to find a 3"ish dia pulley and go with a 3450 rpm pony motor? It just seemed like I wasnt seeing tons of pulley options like I wouldve thought.

    3. What means are you guys implementing to protect the system in the event of a power surge where power goes out and then comes back on like 30 seconds later, to prevent the idler from single phasing on just 2 legs?

    Thanks for any help.

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    It's my understanding that 12 lead motors are typically dual voltage. IIRC you only need 6 leads for star/delta, but I may be completely wrong about that. Post pictures of the nameplate; it will have a wiring diagram on it.

    I have a 5 hp motor starting my 40 hp idler, and it is total overkill. It gets to full speed within about one second. My pulleys are only 3" or 4", but my idler has an odd portion at the end of the shaft where it is much smaller diameter. My idler is 12 wire, and dual voltage. It is not star/delta.

    The size of your idler depends on how long the pony motor can handle the current and how long you want to wait. 1/2 hp is plenty to keep things spinning, should you want to wait for it. Best guess is about 5 seconds. For this sort of inertial load I would maybe consider something like a fan motor or compressor motor that is made for frequent/inertial starts and stops. Worst case make your motor mounts able to handle up to 1 hp, but start out with whatever 1/2 hp motor you have first.

    Pony motor RPM is constrained only by what pulleys you can source/fit.

    A little stupid to use three groove pulleys here, but this is what I could find on my favorite website for stuff like this: https://www.surpluscenter.com/Power-Transmission/Pulleys/Finished-Bore-Pulleys/?page_no=1&fq=ATR_Bore_Fractional:1\-5/8\"

    (They also carry motors, new and used, which is where I got my idler, pony, belts, and pulleys from.)

    As for brown outs, you want to use a magnetic starter. I've had good luck sourcing used contactors from ebay. You'll want the type with auxillary contacts on the side for ease of wiring. You can also just buy new or used magnetic starters.

    But whatever you do, you will want to wire it so that the idler can never start with the pony motor off. In my case I can turn the pony back off after starting the idler, but this is not needed.


    !Be sure to use the datum diameter of the pulley for the given belt size! This is what defines your ratio, not the outside diameter. If you were to use a 3.15" pulley, and a 6.25" pulley you would expect pretty much 3600 rpm and 1800 rpm no load. But the datum diameters are 2.4" and 5.5" respectively for 1/2" belts, giving you an idler rpm of only 1570 rpm at no load, and once the idler is brought online the pony would be forced to run at 4125 rpm. The effect being your idler will have a harder start, your pony will have a hard life, and will be robbing some power from the idler. For this reason it may be best to use two identical pulleys and a matched speed motor to avoid this issue entirely.

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    Quote Originally Posted by Paul Cataldo View Post
    20hp Leeson idler
    FLA = 48a @230v
    1765rpm
    This is a 12 lead motor with 3 sets of 4 leads wired together for the 3 legs, (unlike many 9 lead motors)
    Motor also is inverter duty rated (label states "IRIS Inverter Rated Insulation System)

    I am very limited in electrical knowledge, so bear with me here, but upon googling about 12 lead motors, I am *THINKING* I may have what is called something like a "WYE-START/DELTA-RUN? motor, which can be setup for soft starting or something to that affect? Maybe you guys will know?

    Anyhow, my questions are very basic, and as follows:

    1. What size pony motor should I put on this 300lb monster 20hp idler? Is 1/2hp too small? Should I go with 3/4hp or even 1hp?

    2. I understand fully that either a 1725rpm OR a 3450rpm pony motor can be used, (with proper sizing of the pulley/sheaves) however, upon browsing Mcmaster Carr and ebay for 1.625" bored pulleys for the 20hp idler, I quickly noticed most pulleys are like 6"-7" in diameter. Nothing smaller.
    So this leaves me wondering if I should use a 1725rpm pony motor (same speed as my idler) and try to find a big pulley to match the idler pulley, OR if it would be easier to find a 3"ish dia pulley and go with a 3450 rpm pony motor? It just seemed like I wasnt seeing tons of pulley options like I wouldve thought.

    3. What means are you guys implementing to protect the system in the event of a power surge where power goes out and then comes back on like 30 seconds later, to prevent the idler from single phasing on just 2 legs?

    Thanks for any help.
    I'd submit that "overkill" is actually righteous on a pony-motor, and that the pulley & belt issue gets simpler if pinch rollers off the pallet-jack and caster wheel market are used instead. Been done "right here on PM" more than once.

    Get to "close enough" ratios, put the pony on a tilting or hinged plate such that stepping on the edge or an extended lever off it swings the pony's roller up agin' the idler's roller and closes a switch, same movement, to power the pony.

    Mark One human ear figures the Idler sounds as if it is up to speed, drop contactor / salvaged mag starter onto the line and step off the plate.

    Gravity cooperatively retracts the idler, de-powers it for harmless spin down. No springs required. Battery not required, either.

    S'pose one could remote it with an air line and salvaged Bimba if stashed out back in a doghouse, but even that ain't exactly "high tech", nor in need of exotic clutches or precisely aligned Vee belts.

    Kinda country-boy, but nothing complicated about it, so it works well, costs but peanuts, and lasts a long time.

    2 rollers worth.

    I had PLANNED to use a pony, but found it wasn't complicated to use one of Jim's Phase-Craft to fire-off a 10 HP directly, optionally drop a supplementary 5 HP onto the line, optionally drop it off after a hard-starting load was up, or drop the 10 HP off and run at 5 HP for lighter loads.

    Just the two chunks of rotating Iron and copper, coupla surplus 3PST 3-phase Mercury-Displacement contactors, and its a selectable 5 - 10 - 15 HP RPC, the "run" caps attached to the idler side of the contactors so it balances according to whom is on-duty.

    2 idlers worth, binary logic for quad state: [OFF | 10 | 15 | 5].

    Heaviest and hardest starting load I even own is under 8 HP, RPC are "least inefficient" when NOT TOO-DAMNED terribly oversized, so..

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    Well being that I'm still learning a great deal about motor control and automation etc, I'm wondering just what size magnetic contactor I can get by with here? I mean, the primary reason I went with a pony start system, was to attempt to avoid the high amperage contactors that I know wouldve been needed in a cap start system.
    Is there a way to wire this system up without the need for a huge Nema 3 contactor, but still have power surge protection? IOW's, just use a small size 00 mag etic motor starter for my pony motor only, and still have it wired where the big idler doesnt attempt to start on 2 legs after a power surge? Is this possible?

    As for pics of my motors nameplate, I cannot post them due to mobile phone being my only means of using the net. If anyone cares to accept some pics via email, that would be great.
    FWIW, the motor is 208-230/460v, and low voltage gets 2 sets of 4 leads each wired together, OR high voltage gets 6 sets of 2 wires each wired together.
    Main concern is can I use a small Nema 00 magnetic starter to fire up the pony, and still have power surge protection, with no other huge Nema contactor needed? Or will I need one?

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    Quote Originally Posted by Paul Cataldo View Post
    Well being that I'm still learning a great deal about motor control and automation etc, I'm wondering just what size magnetic contactor I can get by with here? I mean, the primary reason I went with a pony start system, was to attempt to avoid the high amperage contactors that I know wouldve been needed in a cap start system.
    Sorry. No "free lunch" there.

    Per NFPA 70, you will still need the appropriately "rated" switchgear, wire, fuses and/or CB's end-to end REGARDLESS of pony start. That's "the code".

    What pony start does for you is reduce the heavy hammer of starting inrush on the REST of your shop, residence - and any nearby neighbours sharing the same pole-pig, pad-pig, or vault-pig (powerco last-drop transformer).

    "Residential" service ordinarily expects but a FIVE HP motor to be in there somewhere on the "local" grid - eg; under your roof. The air-con outdoor unit compressor usually the most common as is even close to that. Electric clothes dryer, baseboard heat, supplementary heat for a heat-pump, electric range are all basically "resistive" loads, nothing like the inductive kicks of a motor.

    Your idler is a 20 HP MOTOR as far as code sees it.

    Everything else still has to be sized as if the pony did not even exist. PLUS, of course, whatever circuitry it draws its own power from all being code-compliant.

    Not a downside. It is still better "operationally" than that periodic hammer effect.

    Just not any cheaper to implement.

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    Ok thanks termite. If anyone can tell me what size mag starter I need that would help. Can I just go with the motor data chart size? I believe that would be Nema size 3.

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    Quote Originally Posted by Paul Cataldo View Post
    Ok thanks termite. If anyone can tell me what size mag starter I need that would help. Can I just go with the motor data chart size? I believe that would be Nema size 3.
    Yes, of course you can. Mag starters are typically sold BY "Horsepower".

    For simplicity of stocking, many are configurable as either 240 or 480 V as well. Where thermal protective devices AKA "heaters" are included, make sure you select the amperage suited to your 240 V load.

    The starter, y'see has to be able to survive and protect if, for example you simply forget.. to first fire-up the pony. Or its own ephemeral single-phase starter switch or start cap has failed. As they eventually DO.

    Absent either of pony or start cap, it will be a disappointing moment for the twenty-hoss! Loud THUNK, no motive joy.

    But at least nothing vaporizes, catches fire, does a Star wars light show, fries yer ass, or the like.

    Upstream breaker would trip first, here. Square-D's "QO" means "Quick Open". No drama.

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    Is this the motor?
    Attached Thumbnails Attached Thumbnails 20181007_183631.jpg  

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    You're the man Shawn. Copped my pic off GJ forum!

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    Well thermite, sadly I'm looking at Nema size 3 starters on ebay, and theyare not cheap. Especially ones with thermal overload relay and auxillary terminals. I really think a Furnas size 2 1/2 would work, but they are scarce. Dont know if a size 2 would be an option or not.
    Guess I'll have to bite the bullet and drop coin on a size 3.

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    I have a pile of starters, I'll take a look.

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    Thanks so much Shawn!

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    One other question guys. Upon looking at pony motors on ebay, one prospect I've found meets all my criteria, but it is labeled as "Motor rotation RECONN"
    Google fails to tell me what RECONN means. Anyone???

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    Re-connectable? You should have huge selection of used three phase motors in Atlanta on Craigslist etc?

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    Quote Originally Posted by Paul Cataldo View Post
    1. What size pony motor should I put on this 300lb monster 20hp idler? Is 1/2hp too small? Should I go with 3/4hp or even 1hp?
    I built a 30hp in 1981. Used a 3/4hp 1750 totally enclosed 'air over' fan duty motor I got cheap from a local electrical supply house. Ball bearing motor, but not capacitor start. The idler had about a 7.5" pulley on it when I got it.

    Picked up a (relatively) cheap stamped pulley with weld on hub from Tractor supply, slightly larger Pitch Diameter than the idler pulley. It would bring the idler up just slightly past synchronous speed. So, at that point, switch it off, let things coast for 2-3 seconds (down to near spot on synchronous speed) then apply power to the idler. With 2 time delay relays, it was automatic starting. Worked perfectly, with little to no inrush needed to fight the idler Up to or Down to synchronous speed.

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    Isn't motor protection a bit overkill here? If you are worried about the motor trying to start at a stall the branch circuit breaker will take care of that. If you overload the idler with an electrical load you'll know it right away by whatever machine is acting up, and if you overload the motor mechanically you did something very, very wrong.


    And a system that can handle the currents available and drops out when power is lost even if not to code is going to be a hell of a lot better than whatever switch you were going to turn the idler on and off with.

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    Shawn, Atlanta CL is pathetic. However, I'm not looking for a 3 phase motor
    I've already got my 3phase 20hp idler motor. Now I'm just looking for a single phase pony motor. Cheap on ebay. Very scarce on Atlanta CL, as is everything here in the deep south.
    I just need to know what RECONN means as listed on the side of a Leeson motor box under "motor roation"
    May have to call Leeson.

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    Quote Originally Posted by Paul Cataldo View Post
    Well thermite, sadly I'm looking at Nema size 3 starters on ebay, and theyare not cheap. Especially ones with thermal overload relay and auxillary terminals. I really think a Furnas size 2 1/2 would work, but they are scarce. Dont know if a size 2 would be an option or not.
    The Code ALWAYS has more than one acceptable way to do something, so long as the goal is reliably and consistently met. "NFPA" 70 is an extension to a FIRE safety code, after all. Not a one-way-or-the-highway Electrical Engineering design exercise.

    Cheating on the size is not the way. But I need to shut up now. I implement my own "starters".

    "RECONN", BTW, I'd expect on any reversible SINGLE PHASE motor.

    Most are inherently agnostic, need a start-me-the-way-you-mean-to-run-me nudge to continue the march in one direction or the other, thereafter. Re-connect if your need is opposite to what the OEM shipped it with. Diagram is on their dataplate. Or should be.

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    10-4, I'm tracking now on motor selection.The most I've paid for a motor was $100 and it was a 30hp one. Here's a single phase one?

    Lesson 1HP Electric Motor - tools - by owner - sale

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    Well I'll be damned. I usually catch the mis spelled CL auctions but admittedely I'm only subscribed to "LEEson" and not LESSon! Just sent seller a msg. Thanks buddy


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