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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > Please help - X2 mill reversing DC motor mystery
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  1. #1
    Join Date
    Mar 2006
    Posts
    6

    Please help - X2 mill reversing DC motor mystery

    I decided to add simple reversing switch. I have seen similar mods on the net,
    so I thought that it is going to be an hour job. At most. Apparently I was wrong.

    Motor:
    Type: 95D-1
    350W DC Motor 230V
    Class E Reverse

    I have added switch DPDT - FWD/REV. When switch is in FWD position ir works
    without any problem as before. When it is in REV position - it does not work.
    There is no any indication on the motor that power is applied - no sound, no
    movement. When trying to move spindle by hand it just turns freely without
    any resistance.

    How did I tested it so far:

    1. Connected multimeter in parallel to the motor. Strange thing here - in the FWD
    mode, when power is connected (but switch on the pot is in the OFF position) -
    it immediately indicates +90V. Also, when you grab the spindle you can feel that
    it gives more resistance in turning the motor in one direction. When turn the pot
    to the right, passed the switch - voltage gradually changes from 90V to -90V and
    RPM increases as expected.

    When power is applied when the switch is in the REV mode - multimeter shows
    +30V. When turning pot to the right voltage gradually changes from +30V to +204V
    and motor does not work at all

    2. I have disconnected motor from the controller, and connected to 12V DC
    power supply. There was no any reaction from motor in both FWD and REV
    modes.

    3. I have connected motor to 4A bridge rectifier - again, no any reaction in both
    FWD and REV switch positions.

    4. When connected back to the controller - it works just fine, but in FWD direction
    only.

    Why it does not work as expected ? Are there any other tests possible to find
    out what causes this problem ?

    Any helpful answers will be much appeciated.

  2. #2
    Join Date
    Nov 2009
    Posts
    4415

    Re: Please help - X2 mill reversing DC motor mystery

    Why would expect movement from a DC motor requiring 90-130v on a 12v power supply?

    Can you take a photo of the wiring on the DPDT switch and how it goes to the motor? Is the motor connected to center contacts of the DPDT? The way I have seen other motors reverse is by wiring an X on the 4 outer contacts, with power coming in from 1 sides contacts (of those 4). The X reverses the polarity.
    A lazy man does it twice.

  3. #3
    Join Date
    Aug 2006
    Posts
    2758

    Re: Please help - X2 mill reversing DC motor mystery

    Hello;

    Are the brushes on the motor exactly at 180 degrees? If they are offset it might be a uni-directional motor, sometimes employed on the treadmills, etc.

    kreutz

  4. #4
    Join Date
    Feb 2006
    Posts
    7063

    Re: Please help - X2 mill reversing DC motor mystery

    Quote Originally Posted by Fastest1 View Post
    Why would expect movement from a DC motor requiring 90-130v on a 12v power supply?
    Any decent 90V DC will WILL spin on 12V. In fact, it should spin on much less than 12V. For any brush DC motor, voltage controls RPM, current controls torque. Reduced voltage simply means reduced RPM, down to the point where there is not sufficient torque to over-come the internal friction of the motor.

    His switch IS wired incorrectly, but since he hasn't provided any information on how he wired it, not much anyone here can do to help.....

    Regards,
    Ray L.

  5. #5
    Join Date
    Dec 2003
    Posts
    24216

    Re: Please help - X2 mill reversing DC motor mystery

    The reversing switch wired on the KB versions of drive might help, see last page.
    http://www.kbelectronics.com/manuals/kbmd_240d.pdf
    A relay would be wired exactly as the switch and have a centre off position, this ensures you do not go directly from FWD to REV in one motion, notice the switch also connects the drive disable I1 & I2 so that the drive is reset and the accel takes place rather than going from full rpm in one direction to the other.
    I would also expect a 240v motor to move on 12vdc, off load.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  6. #6
    Join Date
    Mar 2006
    Posts
    6

    Re: Please help - X2 mill reversing DC motor mystery

    Please see attached photo of the switch wiring.

    Attachment 261134

    @ Fastest1 - I have tested treadmill DC motor with 12V and 200V (after rectifier) - it was spinning just fine.

    @ kreutz - yes it seems to be regular 180 deg arrangement.

    @ SCzEngrgGroup - I am curious to learn how did you come to conclusion that switch is wired incorrectly

    @ Al_The_Man - thank you for the link. It seems that I have wired the switch just the same way, less the brake resistor.

    What makes me really lost is the fact that motor runs just fine from the controller,
    but refuse to spin in any direction when powered _directly_ either from 12V or from
    200 volt DC. Did anyone experienced anything similar ?

    Second, why in the world I can see on the voltmeter that controller supplies 90V at
    the lowest speed when motor start spinning, and then when turning pot clockwise
    increasing RPM voltage goes from 90V to 0V (at about 50% speed), and then goes
    to -90V at the maximum speed ?

  7. #7
    Join Date
    Feb 2006
    Posts
    7063

    Re: Please help - X2 mill reversing DC motor mystery

    First, go back to basics. Hard-wire the motor to the controller, and confirm that it operates properly, including speed control. Then, reverse only the two motor connections, and confirm that it operates properly in the reverse direction, including speed control. Once done, you have confirmed both motor and controller are working properly, and the switch should be doing precisely what you did by reversing the motor connections in the above test. If it doesn't, then the problem HAS to be the switch itself, or the switch wiring.

    As for the voltage readings, unless you're using an analog voltmeter, you're not likely to get meaningful readings across the motor. The controller is driving the motor with a PWM signal, which is, from the meters point of view, neither AC nor DC, but has characteristics of both that will confuse the electronics in the meter. Once you've run the above tests, and confirmed the motor and controller are both working properly, voltage readings are really not necessary, or helpful, anyway. Resistance readings can confirm that the wiring, and switch, work as expected.

    Regards,
    Ray L.

  8. #8
    Join Date
    Dec 2003
    Posts
    24216

    Re: Please help - X2 mill reversing DC motor mystery

    I noticed on another forum a member with the same motor declared it ran OK in both directions, he also mentioned a uni-direction on the motor plate?
    Out of interest, if you have a meter, measure the resistance on the motor leads on both directions, use the Ohm scale, not the Diode test scale.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9
    Join Date
    Nov 2009
    Posts
    4415

    Re: Please help - X2 mill reversing DC motor mystery

    Judging from your picture of the switch. It appears to me your motor and controller connections are reversed. The motor should be tied to the center taps of the switch in the examples I have seen. It could work exactly the same on your switch as it is.
    A lazy man does it twice.

  10. #10
    Join Date
    Aug 2006
    Posts
    2758

    Re: Please help - X2 mill reversing DC motor mystery

    I second AL_The_Man test. Did you check/clean the motor brushes?

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