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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > A stepper motor is a 2 phase AC synchronous motor?
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  1. #1
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    A stepper motor is a 2 phase AC synchronous motor?

    Hello,
    I have a movable equipment with a 4 leads AC synchronous motor (24V ac, 50/60Hz, 3 watts, 2rpm), I would like to control it easily as stepper in a school project, I've made the connections and indeed it works with full steps and micro steps (I'm still not 100% if there are errors like missed steps, or if it's harmful in some way to the synchronous motor).
    But before going forward, I must be able to explain this clearly.


    I've been doing some research, here are the best sources I have until now:

    «A stepper motor is a 2 phase AC synchronous motor»
    http://venus.ece.ndsu.nodak.edu/~glo...per_Motors.pdf

    «Basically it's a synchronous motor with the magnetic field electronically switched to rotate the armature magnet around.»
    http://minimaestro.as.arizona.edu/MA...es/step101.pdf

    «The AC Synchronous motors provided by Portescap are constructed in the same basic way as the permanent magnet motor except that each coil is supplied with AC voltage with a phase shifting capacitor across the coils.»
    http://www.cas.mcmaster.ca/~lawford/...ef/Stepper.pdf

    «The SLO-SYN motor is unique in that it has the capability of being operated as an AC synchronous, constant speed motor or as a phase switched DC stepper motor. In either case, it is classified as a permanent magnet inductor motor.»
    http://mcsupplyco.com/uploads/images.../SYNCGUIDE.pdf

    example of a synchronous motor datasheet:
    http://www.hurst-motors.com/document...m_Synch_DD.pdf



    I want more, so I would like to learn from other's experience/knowledge.
    I've been reading posts about steppers in this forum with excellent technical insights, can you give me a hand in this matter?

    Thank you

  2. #2
    Community Moderator Al_The_Man's Avatar
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    That is unusually low voltage for a AC stepper, usually they run on 110 or 220vac.
    Some of the advantages are that they run at a constant 72 RPM on 60Hz or 60RPM on 50Hz (synchronous motor).
    The will not burn out when stalled, and have instant stop start.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  3. #3
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    The specs are really uncommon.

    Here are some pictures of the motor:

    Attachment 195298 Attachment 195300 green - original gear reduction; brown - motor


    Further tests showed that this motor alone (without its gear reduction) has 24 full steps per revolution (when driven as stepper).
    From my sources in the previous posts, I interpreted that the expected rpm of this synchronous motor alone (without gear reduction) when driven by Vac @ 50Hz should be:
    (4*60*50)/24 = 500 RPM

    The explanation for the rating of 2 RPM could be that the brand already took its original gear reduction in consideration, that should be a reduction of 250:1.

    Doing this without datasheet is taking some time.

  4. #4
    a stepper motor have 2 phase, 3 phase, 4 phase, 5 phase.

  5. #5
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    Smile Re: A stepper motor is a 2 phase AC synchronous motor?

    I came accross a very interesting website with more info on this product: Synchronous motors, Synchronous engine - All industrial manufacturers - Videos

  6. #6
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    Re: A stepper motor is a 2 phase AC synchronous motor?

    i have a couple of slosyn dc stepper/ac synchronous motors, does anyone know how to wire them for ac synchronous operation? they have 6 wires, 2 are centre of coils and then 2 pairs are the ends of each phase winding, its 4.2v 1.9a 200 teps per rev i think this is the dc spec, some things on nameplate left blank they are M062-FD04 model, great solid motors, like to see if they can be put to good use...

  7. #7
    Community Moderator Al_The_Man's Avatar
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    Re: A stepper motor is a 2 phase AC synchronous motor?

    The Slo-Syn version that were made for operation on the 120v or 240v service were bi-polar - 4 wire two coil motors.
    One pair across the mains power, the other used a resistor and capacitor in series with the second winding.
    CNC, Mechatronics Integration and Custom Machine Design

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

  8. #8
    Quote Originally Posted by elektr View Post
    The specs are really uncommon.

    Here are some pictures of the motor:

    Attachment 195298 Attachment 195300 green - original gear reduction; brown - motor


    Further tests showed that this motor alone (without its gear reduction) has 24 full steps per revolution (when driven as stepper).
    From my sources in the previous posts, I interpreted that the expected rpm of this synchronous motor alone (without gear reduction) when driven by Vac @ 50Hz should be:
    (4*60*50)/24 = 500 RPM

    The explanation for the ratingt of 2 RPM could be that the brand already took its original gear reduction in consideration, that should be a reduction of 250:1.

    Doing this without datasheet is taking some time.
    You said you drove it with a stepper driver? That would suggest it is two independent phase windings. An alternative for a four wire ac-synchronous motor is that it's a three phase with a center tap. Easy enough to just measure with an ohm-meter.

    If you have an oscilloscope and it can be back driven, measure each connected pair with the scope while you back drive at a more or less constant speed. Triggering on the zero crossing should let you capture the waveform nicely.

    I'll bet this is a two independent phase motor, stepper design. Steppers are synchronous motors.

  9. #9
    Community Moderator Al_The_Man's Avatar
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    Re: A stepper motor is a 2 phase AC synchronous motor?

    Quote Originally Posted by StrawberryBoi View Post
    I'll bet this is a two independent phase motor, stepper design. Steppers are synchronous motors.
    Are you confusing this with the original 2013/14 eight year old posts?
    These look like a different motor?
    CNC, Mechatronics Integration and Custom Machine Design

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

  10. #10
    Quote Originally Posted by Al_The_Man View Post
    Are you confusing this with the original 2013/14 eight year old posts?
    These look like a different motor?
    I was responding to the original topic...

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