Reversible Motor Problem

Discussion in 'The Projects Forum' started by oilcan67, Jun 14, 2008.

  1. SgtWookie

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    Last edited: Nov 8, 2009
  2. SgtWookie

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    Here's the schematic for how to connect the 1st switch in my prior post.

    [​IMG]

    [eta]
    You mentioned a white wire instead of a red wire. That probably changes things.

    You need to find out the part number/model number of the motor and post it.
     
  3. CDRIVE

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    As a side note here: OSHA hates simple switches when used on shop type equipment. Sooner or later simple ON-OFF and FWD-OFF-REV switches will be persona none grata, metaphorically speaking. They will be replaced by Latching Contactors that are energized by momentary buttons. This way if the power takes a hit the machine stays off. ;)
     
  4. BMorse

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    You are quite right about OSHA.... It is best to run the motor through an acceptable motor contactor, you can pick these up at a local grainger or Standard Electric might be able to order it for you... Definately McMaster.com has motor contactors/Starters....

    On the other hand, to reverse the motor's direction it is quite acceptable to switch the wires with a relay that is capable of handling the motors current max ratings..... I have attached a simple schematic showing how to connect the motor in discussion to a reversing relay circuit utilizing the 8 pole relay configuration shown also in this thread, since the main objective is to swap 2 wires, there is no need for all these switches and 3 pole relays.....

    I have been following this thread just to see what people come up with and I am sorry if I step on any one's foot by barging in....

    Only 2 switches, and a DPDT relay will do (One heavy duty enough to handle max current draw of motor) (and to comply with OSHA standards a Motor contactor)...

    There has to be an "OPERATE" switch to turn the motor on and off with, (ideally this would be coming from an AC Motor Contactor output). The motor HAS TO BE FULLY STOPED :eek: before reversing it, the motor will keep spinning in the same direction it was originally spinning no matter what state the reversing relay is in if the motor is not completely at a dead stop (trust me on this one...).... Once the motor is stopped then the reversing relay can be activated, then the "Operate" switch can then be turned back on and the motor will spin in the opposite direction....

    Attached is a sketch of how the motor should be connected to the reversing relay and switch, and also, here is the setup I use in an "Industrial/Commercial" product I designed and built :D....

    I am also assuming here that the power is disconnected from the mains before any wiring or fidling around inside happens:)

    My .02
     
    Last edited: Nov 8, 2009
  5. meff00

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    Nov 7, 2009
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    Sarge,
    I had a moment of lucid thought and figured it out. I had correctly used the DPDT to switch my polarity but had not set my hot coming in to shut off. The capacitor was still recieving elec. and therefore could not "reset" to change directions. I solved this by simply installing a house light switch to the "hot" wire coming into the motor. Now i set the direction on the DPDT, and then use the light switch to send the power through. The red and black are my wires I switch to reverse direction. It works and I am very pleased to say your directions, plus a little help from the net, helped me solve the problem.


    I still do not know what a Split phase motor is though. Any help??
     
  6. meff00

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    Nov 7, 2009
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    I forgot to mention in my first post that there is one set of slide connect wires (red and Black) that are used to switch directionality. I realize the 3pdt switch is best but we are building a wheel driven bandsaw lumbermill on a budget and my dad is trying to keep the budget low. Eventually I will convince him to upgrade to a 3pdt (the most simple solution) but until then we will work with the light switch and the dpdt.

    He really wants some type of "paddle" switch but I have been unable to find what he wants. Any IDEAS?
     
  7. SgtWookie

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    Glad you figured it out, but pay attention to what CDRIVE and BMorse are saying. If you have a loss of power when the switch is on, and someone forgets that it's turned on, someone may very well wind up getting injured.

    A split-phase motor is a type of single-phase electric motor. A split-phase motor runs on a single phase and has no special relationship to a split-phase (3-wire) distribution system.
    More info on different types of motors here: http://en.wikipedia.org/wiki/Electric_motor
     
  8. SgtWookie

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    Like I said in the post before, pay attention to what CDRIVE and BMorse said about the pushbuttons and contactors, particularly if you're going to have employees working there.

    A drum switch: http://www.grainger.com/Grainger/items/2BW44?BaseItem=2BW46
    About $129.
    I'd linked to it before, but I guess you didn't see the link.
    Drum switches are what was used in "the good old days".
     
  9. CDRIVE

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    I'm not sure where the Split Phase question came into this thread but the fact that you have a split capacitor or two of them tells me that your motor is a Cap Start - Cap Run Induction motor. They are the most efficient in the induction motor class. The Start Stator and its Capacitor is in the circuit only at start and until it reaches n RPM. The Run Cap is connected at all times and is in series with the Run Stator. ;)
     
    Last edited: Nov 9, 2009
  10. CDRIVE

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    I just noticed that you stated that this is for a home brew lumber mill band saw. I must admit that I've never seen a band saw with a reverse capability. Why do you want this? If reversing the motor also reverses the feed direction then it's a very bad idea. Band Saws have side and rear guides. Reversing the feed will most probably pull the blade off the wheels because there will be nothing to stop it, as there are no front guides! :eek:
     
  11. SgtWookie

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    CDRIVE,
    This is from meff00's first post:
    As to exactly WHAT these Acme screws are driving/controlling, I have no clue. It could be for the side guides to keep lumber aligned/centered on the blade, table angle adjustments, or a myriad of other adjustments.
     
  12. CDRIVE

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    Damn, I keep missing very pertinent information....Kick!! Anyway, If he is driving Acme screws with this motor you can bet it's for feeding the stock into the blade. This would be useful and desirable when the blade is not in contact with the stock being cut. Otherwise the blade will be yanked off the wheels. On the other hand, the screws may be for lining (lateral movement) up for the next cut.
     
  13. SgtWookie

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    I think it's unlikely that they're using an Acme screw to feed lumber stock into the blade; particularly if they're starting off with logs. An Acme screw drive would have to be VERY long to be of much use (thus large in diameter and VERY expensive), and the constant speed of the feed would not likely utilize the saw at an optimal feed rate; it would nearly always be too fast or too slow, and the return stroke would almost always be too slow.

    OTOH, the lateral alignment of the lumber with the blade would be a practical application for an Acme screw. It might be a bit dicey getting the alignment just right. I think I'd opt for a universal motor with speed control and braking instead of a capacitor start fixed-speed motor; that would give much more precise control.
     
  14. CDRIVE

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    Yes, I should have put more thought into that bit of speculation. I think it's technically known as "Putting mouth in gear before engaging brain! :rolleyes:
    I can make a promise that it won't be my last time.:D
     
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