Foot switch rates for 2 hp three phase motor
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  1. #1
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    Default Foot switch rates for 2 hp three phase motor

    I have a drill press with a 2 hp, three phase motor. After reading this forum and stumbling upon a great idea, I order a Linemaster cast iron foot switch to run constantly in reverse and the momentary footswitch when depressed changes rotation, “instantly”.
    This will be awesome for tapping.
    It was awesome....
    Then I fried the micro, DPDT switch inside the foot pedal. Hmmm I believe it is rated for 16 amps, 250V AC. It is also rated for 1/2hp.
    I obviously read the amp rating on the motor and assumed it would be more than double the normal amp draw.
    What should I do? Order another momentary DPDT switch to throw inside the really nice pedal , rated even higher? Or contact the manufacturer and see if they recommend another really expensive footswitch. It’s just a set of lever snap switches inside the cast iron housing, how hard is it to find one that fits?
    Other issues I haven’t thought of like high current rush when plug reversing? Still rated at double.
    Either way thanks to this forum for the idea even if it isn’t ironed out yet.

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    You need a reversing motor starter.

    Or just buy a tapping head.

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    b39a20e9-f8da-4280-b138-d1dc5054478f.jpgb39a20e9-f8da-4280-b138-d1dc5054478f.jpgI think I may have missed a few important details on the design. I need to look into the motor starters. It clearly says that in the post in referenced, i guess.

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    Tapping head is just as quick and a whole lot less stress on the motor. You have the RMS of the current + the arc energy. The poor switch wasn't designed for that.

    Tom

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    See if you could use this with your foot switch


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by Cmachine84 View Post
    b39a20e9-f8da-4280-b138-d1dc5054478f.jpgb39a20e9-f8da-4280-b138-d1dc5054478f.jpgI think I may have missed a few important details on the design. I need to look into the motor starters. It clearly says that in the post in referenced, i guess.
    No, not really, you do not.

    You do yourself NO favours by applying a bigger hammer to the wrong end of a center punch.

    Get that tapping head.

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    well, i dont know much about this, but my 5.5 kw lathe has instant breaking/reverse and the motor apparently has survived for decades.

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    Quote Originally Posted by dian View Post
    well, i dont know much about this, but my 5.5 kw lathe has instant breaking/reverse and the motor apparently has survived for decades.
    Are you doing it with a foot switch rated for 1/2 hp ?

    "Plug reversing" is acceptable, however how many times per hour you do it is
    a factor in this.

    A D.P. with a rigid tap holder would probably see 10x more plug reversals
    per hour than the lathe.

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    I'm going to bet that where you're at, it's illegal for the operator controls to be more than 120 VAC. That's why you don't see foot switches and palm buttons rated for 3 phase. Got to go through a motor starter.

    Tapping head is still a better choice.
    JR

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    Do it right,buy a double acting forward and reverse foot switch that is spring loaded and is always off unless you step on it.I mounted mine on a piece of half inch cold rolled and wired it through a double pole double throw relay this saves the micro switch on the foot switch.Tapping heads are nice,but they are not very convenient when you need to tap one or two holes real quick. I have used tapping heads many times.People have been tapping by reversing 3 phase motors for 60 years with Bridgeports a drillpreses.It is my opinion,that EVERY drillpres MUST have a foot switch .I consider it a convenience and a safety issue. Edwin Dirnbeck


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by edwin dirnbeck View Post
    It is my opinion,that EVERY drillpres MUST have a foot switch .I consider it a convenient an a safety issue. Edwin Dirnbeck


    Sent from my iPhone using Tapatalk
    That is a safety issue for sure.

    No toe guard to keep you from accidentally stepping on it.

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    Quote Originally Posted by JRIowa View Post
    I'm going to bet that where you're at, it's illegal for the operator controls to be more than 120 VAC. That's why you don't see foot switches and palm buttons rated for 3 phase. Got to go through a motor starter.
    Yup, came across a lighting breaker panel that is legal for the occupants to switch
    the lights on/off with. I see them everywhere, perfectly fine as you are switching
    120 vac.

    Until they started switching the 480 3 phase stuff too.
    And then the handle broke off, and they started jamming a large screwdriver
    into the breaker to switch it every day.....

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    Quote Originally Posted by digger doug View Post
    Are you doing it with a foot switch rated for 1/2 hp ?

    "Plug reversing" is acceptable, however how many times per hour you do it is
    a factor in this.

    A D.P. with a rigid tap holder would probably see 10x more plug reversals
    per hour than the lathe.
    i use it whenever i stop the chuck.

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    There is a right way, a wrong way and a duck tape way of doing things. The unprotected foot switch is a wrong (illegal) way, the foot switch directly controlling a 2 HP motor is a duck tape way and illegal if used for more than 120 VAC. Either get a reversing motor controller or a tapping head.

    The most convenient way would be a covered foot switch controlling a reversing motor starter and with a selector switch for either foot switch or manual control. You should also have an adapter between the tap (square head) and the drill chuck (3 jaw).

    Tom

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    Ignorance of proper use of a foot switch is no excuse, however I was attempting to do what I thought was acceptable. Thanks for the replies so far.
    I would still like to make the press and motor function as described. Do all reversing motor starters have an option for a foot switch? Any suggestions on which controller would be appropriate? I believe three phase , 208v and two hp motor are all the specs required for suggestions.
    I have three phase direct so I did not immediately go the route of VFD with footswitch. Seems harder to find a three phase input VFD than most hobby guys looking to power three phase things in their garage off of a single phase dryer outlet.
    Will I be smarter and cheaper going VFD route even though I don’t necessarily need the speed control and phase conversion?
    I don’t think I care about immediate reverse and dynamic braking etc. I can deal with a few seconds wind down and reverse.

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    Also, did I post incorrectly? I saw the thread was moved and can’t seem to see which section it was moved to. Let me know.

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    The thread was moved to the transformer section. As far as reversing, it is only necessary to interchange two of the three wires going to the motor. The foot switch selectively operates the coil to two interlocked contactors/starters with a center position of off. One contactor is wired straight through, the other has two of the three phases swapped.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    The thread was moved to the transformer section. As far as reversing, it is only necessary to interchange two of the three wires going to the motor. The foot switch selectively operates the coil to two interlocked contactors/starters with a center position of off. One contactor is wired straight through, the other has two of the three phases swapped.

    Tom
    ....and they are mechanically interlocked....


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