Vector motors

Discussion in 'The Projects Forum' started by aggieracer, Dec 5, 2013.

  1. aggieracer

    Thread Starter New Member

    Dec 5, 2013
    2
    0
    I am working on a project where we want to run at a large range of speeds.
    .03ft/min to 600ft/min. The motor I have runs a 12.5" dia drive drum.

    Right now I am able to run the 600ft/min at 62Hz but the low range is where I am running into problems. I am using a 1000:1 vector motor and allen bradley 755 drive. In order to run the .03ft/min with my 10:1 gear reduction I need a output frequency of .003Hz. Is this even possible with a drive?
    Has anyone ever run this large of range without secondary gearing?
    Here are my motor specs.
    Specifications: ZDVSM3661T
    SPEC. NUMBER:
    06H928X181Z1
    CATALOG NUMBER:
    ZDVSM3661T
    FL AMPS:
    8.2/4.1
    BEARING-DRIVE-END:
    6206
    BEARING-OPP-DRIVE-END:
    6206
    BLOWER-AMPS:
    --
    BLOWER-HERTZ:
    --
    BLOWER-PHASE:
    --
    BLOWER-VOLTS:
    --
    DESIGN CODE:
    B
    DOE-CODE:
    010A
    FL EFFICIENCY:
    89.5
    FRAME:
    182TC
    HERTZ:
    60
    INSULATION-CLASS:
    F
    MAGNETIZING-CURRENT:
    4.2/2.1
    MAXIMUM-RPM:
    5400
    SPEED [rpm]:
    1755
    OUTPUT [hp]:
    3 TE
    PHASE:
    3
    RATING:
    40C AMB-CONT
    ROTOR-INERTIA:
    0.3
    SERIAL-NUMBER:
    --
    SERVICE FACTOR:
    1.00
    SLIP-HERTZ:
    1.5
    VOLTAGE:
    230/460

    What does slip-hertz mean? Does this mean the motor will slip under 1.5Hz? This is below the 1000:1 ratio. Should I not get full torque at .06Hz?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,510
    2,369
    I haven't looked at all the issues, motor and VFD details, but .003hz is asking too much from a VFD, particularly without feedback, slip herz is slip frequency, the difference between the applied frequency and the actual rpm, an induction motor can never run at synchronism, a slip frequency is going to occur in order for induction to occur.
    Max.
     
    strantor likes this.
  3. aggieracer

    Thread Starter New Member

    Dec 5, 2013
    2
    0
    Thanks max. I am running with encoder. 1024ppr.
    Is it a good idea to never run below the slip frequency for motor startup?
     
  4. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    .003Hz is one electrical cycle every 5.6 minutes. Even if your VFD were capable of this, I doubt there would be any resultant motor movement. I think you will need quite a few multi-speed gearboxes to achieve such a wide range of speeds.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,510
    2,369
    The slip or frequency difference is going to vary with load etc, e.g. a 60 hz induction motor, no VFD, at start up the slip freq. is naturally 60hz, and will decrease as the rotor catches up with the rotating field, with a VFD you have the option of programming the acceleration (maintain a lower slip freq).
    As you may have found out, if you try to accell too fast (high slip freq), the VFD will trip the over current.
    Max.
     
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