Rotary Phase Converter Questions
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  1. #1
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    Default Rotary Phase Converter Questions

    I have some threads going where I have been asking about VFD's. A couple people suggested them in my lathe specific thread too but I am taking a pause and considering a RPC. It may cost more but that is not a primary motivator for me. The VFD looks exponentially more complex for me procure all the necessary parts and then wire them and program the VFD to get up and running.

    If I go with a RPC it looks like darn near plug and play. Whats the catch? I can think of a couple things that I want to ask about first.

    I am in a tropical humid environment. I have a dehumidified garage/shop but it's still around 55% humidity inside there. Is that any concern for me?

    I would do a wall mount control box and place the motor down out of the way.
    I see that some of the suppliers have self contained boxes for the motors to be put outside with cooling fans, etc. I don't think I would put mine outside but can you use this outside setup inside your shop to keep the motor quieter? Plus it's warm here and I don't have AC (yet) but it can be 85-90 inside. I prefer to work earlier in the morning when it's cooler but is that an issue for these setups?

    My lathe came from a shop that had 3 phase power so it is still wired with a heavy gauge power chord that is about 20-25 feet long and a plug. Are there any limitations with the RPC to the power chord length? The idea to order a RPC with a breaker and a female 3 phase plug and just hit the ground running is appealing to me.

    My lathe has an old fashioned breaker and a nice drum switch that I can just leave as is if I go with the RPC right?


    What brands of Rotary Phase Converters should I be looking at. SO far I have found American and North American with a West Coast distributor for North American so that's looking good.

    Thanks for any feedback and thoughts here guys.

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    If you are in Hawaii and want an rpc, I would recommend just buying the control box and sourcing a used motor for the idler locally. If you are so inclined, you could also just build your own control box, there are plans on this site, not terribly hard if you understand it. 30 ft cord is fine, yes leave controls alone in lathe.

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    I have a question about wiring the RPC. My lathe was last in use in a shop that had 3 Phase power with a 30 Amp circuit breaker and has a long power chord with a 30 Amp rated 4 prong twist plug. I am assuming it the correct wire spec for 30 Amp which is 10ga wire if I am not mistaken. I have a few open double 20 Amp breakers in my junction box and was hoping to use one of them for my lathe and wiring a RPC to this. Is there any problem going from the phase converter to the lathe with heavier gauge wire? In other words, If my power chord is using heavier wire than is needed for a 20 Amp circuit is that a problem for an RPC setup? Are there other considerations that I should be thinking about?

    I am looking seriously at an American Rotary AD05 5hp unit.

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    Since you haven't mentioned the hp or voltage of the motor, its difficult to say what is right or wrong.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    Since you haven't mentioned the hp or voltage of the motor, its difficult to say what is right or wrong.

    Tom
    Oh here is the motor tag...

    img_6259.jpg

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    Per manual AR 5 wiring recommendations, minimum single phase 240VAC breaker size is 20A with 10AWG wire, 3-Phase output 12 AWG. I would probably go with a 30A breaker and 10AWG input, RPC output minimum 12AWG although no problem with using a heavy gauge wire. Wire size is based on no more than 50' wire length to minimize voltage drop.

    Due to shipping costs, it may be worthwhile to just purchase a RPC panel and source an idler motor locally, probably go with a TEFC or TENV 1750 RPM motor due to the enviroment.

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    Quote Originally Posted by mksj View Post
    Per manual AR 5 wiring recommendations, minimum single phase 240VAC breaker size is 20A with 10AWG wire, 3-Phase output 12 AWG. I would probably go with a 30A breaker and 10AWG input, RPC output minimum 12AWG although no problem with using a heavy gauge wire. Wire size is based on no more than 50' wire length to minimize voltage drop.

    Due to shipping costs, it may be worthwhile to just purchase a RPC panel and source an idler motor locally, probably go with a TEFC or TENV 1750 RPM motor due to the enviroment.
    Thanks for the details on what kind of motor to look at. I will check it out but I have pretty thick skin on shipping costs so that's why I try to make darn sure it's the best choice for me and then I order, pay...cry once and don't look back!

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    I got the motor and the Phase converter shipped to my door for 200 which is not terrible for where I am. I had to use a California reseller who advertises on Ebay to get this number it was twice as much to ship form American Rotary Direct! I am getting ready to have some 220 pulled to where I want it but I have a few questions from you guys who have used these things before plus I have a few electrical items that can be incorporated into the wiring setup.

    elec-stuff.jpg

    I have a three phase safety switch and a breaker that I can use inbetween the RPC and the lathe motor. The lathe has this same breaker wired to the extension cord already and mounted on the back of the lathe and this is a replacement that I sourced. I am not sure I need it depending on how I wire up the garage.

    The RPC has knock outs on the bottom for a panel mount breaker and "hopefully" room for a female 4 prong twist lock plug? Do any of you guys run your RPC this way, with the breaker and connector on the bottom? If I go this way it wont be so easy to use the lever safety switch but I could come out of the RPC to the switch and back in for a cleaner install. I am not sure what the best combo is to keep my machine and the RPC protected from our less than ideal electrical grid!

    I am planning for a 30A breaker at the main junction box and then to the input of the RPC and then I am less sure of what path to take. Am I over thinking it. I have lost a lot of valuable things over the years because of power spikes during electrical storms so I am a little gun shy.

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    Quote Originally Posted by Kevin T View Post
    I am planning for a 30A breaker at the main junction box and then to the input of the RPC and then I am less sure of what path to take. Am I over thinking it. I have lost a lot of valuable things over the years because of power spikes during electrical storms so I am a little gun shy.
    Breaker --> Switch --> RPC --> Machine.

    You should look into the VFD possibilities in case a lightning strike hits the RPC.

    It's better to be knowledgeable about both the RPC and VFD.

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    Quote Originally Posted by Kevin T View Post
    Oh here is the motor tag...

    img_6259.jpg
    If this is the machine motor tag:
    Your idler should be 2Hp or greater. A 5Hp motor would be top end.

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    Quote Originally Posted by rons View Post
    If this is the machine motor tag:
    Your idler should be 2Hp or greater. A 5Hp motor would be top end.
    5HP is the smallest they sell so that's what I got!

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    Quote Originally Posted by Kevin T View Post
    The RPC has knock outs on the bottom for a panel mount breaker and "hopefully" room for a female 4 prong twist lock plug? Do any of you guys run your RPC this way, with the breaker and connector on the bottom?
    I would use a small distribution box underneath the RPC box. The distribution box can be cut up for the outlet(s).

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    Quote Originally Posted by rons View Post
    Breaker --> Switch --> RPC --> Machine.

    You should look into the VFD possibilities in case a lightning strike hits the RPC.

    Having both a RPC and a VFD is a good thing.
    The VFD manual scared me out of installing it with all the recommended buffers, filters, conditioners, etc that it said were necessary but I kept it to sell or trade. Hopefully I don't need it. When we are having electrical storms I shut off breakers these days to protect my toys.

    Thanks for the simple run down of the order of things. That switch I have is rated for three phase with three poles inside. Is it OK to use it in between the main panel and the RPC with just the two single phase wires? Or is a ground wire in the mix and gets hooked up too? I do like that switch for the visible on/off. I don't really want to buy another one but maybe it won't be to code?

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    Quote Originally Posted by Kevin T View Post
    That switch I have is rated for three phase with three poles inside. Is it OK to use it in between the main panel and the RPC with just the two single phase wires? Or is a ground wire in the mix and gets hooked up too? I do like that switch for the visible on/off. I don't really want to buy another one but maybe it won't be to code?
    As long as it is rated for the amperage, I would say yes (but an inspector may say no).

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    Quote Originally Posted by Kevin T View Post
    The VFD manual scared me out of installing it with all the recommended buffers, filters, conditioners, etc that it said were necessary but I kept it to sell or trade. Hopefully I don't need it. When we are having electrical storms I shut off breakers these days to protect my toys.

    Thanks for the simple run down of the order of things. That switch I have is rated for three phase with three poles inside. Is it OK to use it in between the main panel and the RPC with just the two single phase wires? Or is a ground wire in the mix and gets hooked up too? I do like that switch for the visible on/off. I don't really want to buy another one but maybe it won't be to code?
    If space and/or placement convenience is an issue, look into a "rated" and code-compliant "rotary disconnect" with lockout tab. ISTR I paid $25 to $35 each for several 20A, 30A rated "NOS" and they were brand-new and even Made in USA.

    Those fit into ordinary boxes, including the rugged cast "Bell" boxes most often utilized for outdoor outlets. Larger is better what with wire-count and size, but that is still a lot more compact than many other options

    Boxes of that sort generally have screw-in plugs rather than "leaky" knock-outs, as well as gaskets for their covers. Those work for keeping swarf and coolant out if mounted on or near the machine-tool or anywhere else splash or fine dust or seasonal pollen, insects, etc. might otherwise be an issue.

    "Upstream" I have the same family of Square-D "QO" load-center as used for commercial 3-Phase power. The world uses a ton of them, so the cost "NOS" was LESS for a large one than small. Spacing the breakers out rather than filling all slots makes it easier to wire and easier to select which is what when reaching for a breaker to power a given branch on or off, etc.

    Fuses work, but... an event as blows a fuse can often open but one or two, leaving one or two still "hot".

    A Common-trip breaker opens all of its "hot" legs.

    And don't go altering NEMA rated boxes. No need. There is a "rated" solution to most ANY requirement already.

    Altering them is akin to trying to teach a pig how to whistle.

    Wastes your time, annoys the pig.. and pisses-off inspectors or inch-hoorance claims adjusters.


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    Quote Originally Posted by dalmatiangirl61 View Post
    As long as it is rated for the amperage, I would say yes (but an inspector may say no).

    The motor switch really needs to be rated for the motor HP (for what it controls). That will take care of switching off with locked rotor current flowing, etc. Motor controls are generally HP rated in the US. Avoids many questions and calculations.

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    Quote Originally Posted by JST View Post
    The motor switch really needs to be rated for the motor HP (for what it controls). That will take care of switching off with locked rotor current flowing, etc. Motor controls are generally HP rated in the US. Avoids many questions and calculations.
    The contactors used to build them are "usually" DUAL-rated, actually.

    Half - or less, sometimes not at ALL - for DC use than for AC use.

    Dunno WHY so many folks want to fight it or re-invent bog-standard wheels. May as well carve yer own motor vehicle tires out of solid rubber stock?

    Code, NEMA, UL, CSA... all that stuff is tested, labeled, published. Far, far, easier to comply with codes than to NOT comply with them. Usually faster if not also CHEAPER as well.

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    Quote Originally Posted by Kevin T View Post
    The RPC has knock outs on the bottom for a panel mount breaker and "hopefully" room for a female 4 prong twist lock plug? .
    Suggest you use a female twistlock cord cap on a short pigtail, which will hang downward. Machine cord with male cord cap
    connects to that. A twistlock connector setup like that will serve as a positive disconnect for safety.

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    Quote Originally Posted by jim rozen View Post
    Suggest you use a female twistlock cord cap on a short pigtail, which will hang downward. Machine cord with male cord cap
    connects to that. A twistlock connector setup like that will serve as a positive disconnect for safety.
    ?? Bulkhead mount Hubbell will serve better-yet, generally lower priced and easier to terminate the wire to than SO cord mounts are.

    Conduit, sealtite, ELSE close-nipple a proper BOX to it for the twist-lock is what should be done. Lets you position and aim it proper for ease of use. Code ain't keen on that as a "disconnect" you place it where yah have to get on your belly or knees to activate it as such.

    Not as if box and cover cost anything compared to the twist-lock's price and not as if you had to cram it into the instrument panel space on a hang-glider, either.

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    Quote Originally Posted by Kevin T View Post
    The VFD manual scared me out of installing it with all the recommended buffers, filters, conditioners, etc that it said were necessary but I kept it to sell or trade. Hopefully I don't need it. When we are having electrical storms I shut off breakers these days to protect my toys.

    Thanks for the simple run down of the order of things. That switch I have is rated for three phase with three poles inside. Is it OK to use it in between the main panel and the RPC with just the two single phase wires? Or is a ground wire in the mix and gets hooked up too? I do like that switch for the visible on/off. I don't really want to buy another one but maybe it won't be to code?
    The way to not get scared is do not read a VFD manual on Halloween.

    Just keep reading it over and over until it sinks in.

    Just pass the two single phase wires on the two outside poles of the switch and leave the middle pole position open. The ground wire is not connected there.

    What is the switch rated for?
    What VFD do you have?


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