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  1. #16
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    Hi Steve,

    That looks pretty straight forward, the M1 M2 contactors are reversing the polarity to the start winding connections on motor terminals 5 and 6, but that's not your motor.

    Are the motor contactors still in the electrical enclosure? Any chance of a picture of how they are connected?

    Regards
    Ray

  2. #17
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    Quote Originally Posted by RayG View Post
    Hi Steve,

    That looks pretty straight forward, the M1 M2 contactors are reversing the polarity to the start winding connections on motor terminals 5 and 6, but that's not your motor.

    Are the motor contactors still in the electrical enclosure? Any chance of a picture of how they are connected?

    Regards
    Ray

    Hi Ray,
    There are NO contactors. Its a 240V plug top, a terminal strip, a rotary switch ( with parts missing ) and the Motor.
    IMG_0004 (Medium).JPG

    It looks simple....lol

  3. #18
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    Quote Originally Posted by Stustoys View Post
    Hi Steve,
    If you do much thread cutting you'll want reverse sooner or later.

    Hi Ray,
    Assuming Steve's diagram is correct except M6 is indeed a center tap of the run winding.
    Lets say
    V=active
    U=neutral
    M6=neutral
    What if we swap to V=neutral and U=active, leaving M6=neutral.
    Havent we reversed things?
    I really have no idea and am just having a stab. Dont try this at home

    Stuart

    I just went a explored this theory and it looks like this is indeed the case. ( neglected to measure ohms from both cap wires to either end of the run winding. I get ~3.5 ohms from one of the cap wires to each end of the run winding.
    So it looks like the run winding has a centre tap to the state winding and cap! ( I've never seen/heard of this before....)
    It also looks to me that a U/V swap might reverse the motor, as Stuart speculated.
    It also looks as if a simple 3 pole, 3 position switch will do the job as well.
    When I get a new cap I will test it out.
    IMG_0003 (Small).JPG

    What do you guys think?


    Steve

  4. #19
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    Quote Originally Posted by Sterob View Post

    What do you guys think?


    Steve
    If it were mine I'd give it a go, you can't hurt anything to try.

    Regards
    Ray

  5. #20
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    Default How to reverse a Cap start motor with only 3 wires a terminal box?

    Steve,
    Are you sure there is no centrifugal start switch?


    Edit: it probably doesn't make any difference to the circuit you posted anyway.
    Chris

  6. #21
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    Hi Ray,
    I think it is kicking the other way....... but I wouldn't bet much money on it lol

    Hi Steve,
    That's along the same lines as the drawing I came up with. Though I have no idea if its strictly correct (or even loosely correct) .

    Does your lathe have the shaft for On/Off/Rev on the carriage as per the one in the picture? Mines like that and has a third contactor so the lathe wont restart until the lever is returned to "Off"

    Stuart
    Attached Images Attached Images

  7. #22
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    Quote Originally Posted by jack620 View Post
    Steve,
    Are you sure there is no centrifugal start switch?


    Edit: it probably doesn't make any difference to the circuit you posted anyway.

    Have not pulled the motor down to check yet...no time....
    I'm not sure it matters either....It might pay for me to do that before I go any further.

  8. #23
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    Quote Originally Posted by Stustoys View Post

    Does your lathe have the shaft for On/Off/Rev on the carriage as per the one in the picture?
    No, it just has a single rotary switch and no contactors at all.

  9. #24
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    Quote Originally Posted by Sterob View Post
    I just went a explored this theory and it looks like this is indeed the case. ( neglected to measure ohms from both cap wires to either end of the run winding. I get ~3.5 ohms from one of the cap wires to each end of the run winding.
    So it looks like the run winding has a centre tap to the state winding and cap! ( I've never seen/heard of this before....)
    It also looks to me that a U/V swap might reverse the motor, as Stuart speculated.
    It also looks as if a simple 3 pole, 3 position switch will do the job as well.
    When I get a new cap I will test it out.
    IMG_0003 (Small).JPG

    What do you guys think?


    Steve
    That wiring diagram makes sense and I agree it would simplify forward/reverse switching. I've never seen that kind of arrangement before either.

  10. #25
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    Quote Originally Posted by BaronJ View Post
    That wiring diagram makes sense and I agree it would simplify forward/reverse switching. I've never seen that kind of arrangement before either.

    That makes me a little nervous that no-one has seen this arrangement before.....but it seems to make sense.
    Also weird( and NOT helpful ) that the manual shows a 4 wire motor I actually have a 3 wire motor......

    Thanks for all your input guys. Sorry I made assumptions about things that make it harder to help. ( I should have known better...one of my pet hates....lol )

    These things happen when you take on 'love jobs'..lol.

    The new cap should be here early next week, so I can try the smoke test.

    Steve

  11. #26
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    Steve,
    this doc might help. There are various single-phase motor configurations shown on page 8.

    Also on p8 is the following:

    Most single phase motors can be reversed by swapping the connections to the start winding with respect to the run winding. However not all motors have sufficient connections brought out to allow this to be done, in some cases they can be found by opening up the motor but in others the connections are permanently made inside the windings and will need expert attention to reverse them.

    Chris
    Attached Files Attached Files

  12. #27
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    Quote Originally Posted by jack620 View Post
    Steve,
    this doc might help. There are various single-phase motor configurations shown on page 8.

    Also on p8 is the following:

    Most single phase motors can be reversed by swapping the connections to the start winding with respect to the run winding. However not all motors have sufficient connections brought out to allow this to be done, in some cases they can be found by opening up the motor but in others the connections are permanently made inside the windings and will need expert attention to reverse them.

    Chris

    Thanks Jack, thats a handy pdf.
    I might have to buy a copy of Rosenberg. Have been threatening to for ages....It always been the 'bible' for me.

  13. #28
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    I've found some rotary switches on Ebay ( on/0ff/0n and 5 pole, I think ) so when they get here, I'll try the smoke test.

    I've also just bought a copy of Rosenberg. I can't get my money's worth out of it if I don't own a copy, can I?....lol
    At $200 it not cheap, but I hope its worth it....

    I'll post with success/failure...info....

    Steve

    Rotary Switch.jpg

  14. #29
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    Looking at the circuit in the original post, I have been told that the split run winding is utilised by the manufacturer to make the one motor work on 110 or 220 volts, for the two world markets.
    The capacitor only needs to be rated 125 volts for either situation.
    The motor specification label may not mention dual voltage ability.
    This type of motor is very commonly used on economy drill presses etc.
    My 1984 Taiwanese "Rexon" drill press has this very same wiring concept.

    To enable a motor reverse, you normally have to take the motor down and find the internal connection point on the run winding, so as to completely separate out the start and run windings.
    Then it is normally an easy matter to bring all winding connections out to your motor control switch.
    Be aware that some types of centrifugal switches, if used, favour one motor direction only.

    In my drill press, I have broken all the rules by replacing the start capacitor with a 8 mfd 250 V AC rated polyester type instead of an electrolytic type.
    It was originally used as PF correction in an old fluoro light fitting.
    Yes, eight mfd.
    The drill press has a nice soft start, and the motor doesnt get too hot.


    cheerio, mike

  15. #30
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    Default Motor Test

    I received the new Caps today and wired it up as my diagram modified by Stu in post #10.
    I'm happy to say that that diagram is correct. There IS a centrifugal switch on the start winding circuit.
    Swapping the U and V connections does give opposite rotation.

    The only thing of concern is the current draw is little high at 9.2A with no load.
    The name plate says its a 240V ,1 HP motor and FLC is 7 amps.

    The 400uF Cap would not fit under the housing, so I used a 240V , 200uF Cap. There was no difference to the way the motor started and the NLC was still 9.2A.

    The motor is either REALLY a 220V motor ( the incorrect 1 phase wiring diagram mentions 220v ), there is an error on the name plate, or the motor is beginning to fail. I don't have a Megga the winding resistance to earth although my RCD's in the shed have not tripped.

    I don't have a reason to suspect its failing ( besides the higher than expected current draw) as the original fault was the control switch 'fell apart'.

    This journey is almost over.....

    Steve

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