Brush shift/S-charge AC motor

Discussion in 'Komori Printing Presses' started by Abhi, Oct 10, 2017.

  1. Abhi

    Abhi Member

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    Anyone having in-depth info about the main motor(with movable carbon brushes) of older komori models.

    More importantly is it possible to drive it via a variable frequency drive to improve efficiency?
     
  2. presselectronics

    presselectronics Senior Member

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    Sorry, unlike the wound rotor motors on older presses, you cannot easily adapt a freq drive to this motor.
     
  3. Abhi

    Abhi Member

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    Thanks for the reply.
    I have a very curious case.
    The press has forward and reverse inching and slow (continuous inching) functions being done through a VFD.
    The slow running mode bypasses the drive and the motor starts running.
    The fast running mode increases the speed and the drive remains bypassed.
    This control of using the drive or bypassing it is done using two external contactors,(relays).

    Currently, there is no speed control in this press and only 3 speeds are available-
    1) Slow, inch reverse through VFD
    2) slow running, bypassing VFD.
    3) Fast running, bypassing VFD.

    Any ideas why would someone do thist?
     
  4. presselectronics

    presselectronics Senior Member

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    My guess would be that the brush shifting motor's slowest speed is not slow enough.
    Sometimes the slowest speed was not slow enough to wash up easily by hand.
    Or the commutator brush shifting section was not set right, or damaged, etc.
    How slow is the freq drive at slower or inch speed?
     
    Abhi likes this.

  5. Abhi

    Abhi Member

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    Location:
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    Thanks for the input. Can be the reason. We always feel that the machine is a bit fast for washup.

    We have been successful in changing the VFD parameters to reduce the speed.
    The VFD currently runs at 16Hz Frequency on inching and slower speed.

    The slow running, bypassing VFD, is 3000sph.
    The fast running, bypassing VFD is around 8000sph.
    Speed increase decrease function doesn't work.

    Also, I feel that the brush moving motor doesn't work. I'm still wondering, is it possible by some other way by which the speed jumps from 3k to 8k without the brush shifting mechanism in place.
     

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