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IndustryArena Forum > CNC Electronics > Phase Converters > Controlling/adjusting spindle decel ramp speed Okuma LC20
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  1. #1
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    Sep 2020
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    1

    Controlling/adjusting spindle decel ramp speed Okuma LC20

    Hi All
    I have an Okuma LC20 being run off a rotary phase converter (8kw) with a large 30 hp idler motor in parallel. Being in country Australia the supply is 230v single phase with no 3 phase available. I have added the 30 hp idler as it supplies the extra grunt to accelerate the DC spindle without any loss of phase errors occurring. My problem is that I have overvoltage error anytime I stop/slow the spindle from a speed greater than 100 rpm. I am sure this is happening because the SDU600-w driver tries to feed the excess dc bus voltage back upstream into the phase converter. Normally a utility 3 phase supply grid would happily accept this charge but not in my situation.

    Is there anyone with knowledge of the machine/ SDU600-w driver who has modded to allow a slower decel rate ? I am aware that I could g code the problem away by creating a macro involving dwell to step reduce the ramp rate but I would prefer to do something off the driver board. Maybe bring in to play a switch/ resistors to dump the excess voltage as regenerative braking won’t suffice. Thanks Phil

  2. #2
    Member
    Join Date
    Jun 2010
    Posts
    4008

    Re: Controlling/adjusting spindle decel ramp speed Okuma LC20

    I THINK the problem is slowing down the 30 hp motor.
    Try running without it. If that means slowing down the accell a little, fair enough.

    Cheers
    Roger

  3. #3
    Member
    Join Date
    Jan 2005
    Posts
    11408

    Re: Controlling/adjusting spindle decel ramp speed Okuma LC20

    Quote Originally Posted by Tarakai View Post
    Hi All
    I have an Okuma LC20 being run off a rotary phase converter (8kw) with a large 30 hp idler motor in parallel. Being in country Australia the supply is 230v single phase with no 3 phase available. I have added the 30 hp idler as it supplies the extra grunt to accelerate the DC spindle without any loss of phase errors occurring. My problem is that I have overvoltage error anytime I stop/slow the spindle from a speed greater than 100 rpm. I am sure this is happening because the SDU600-w driver tries to feed the excess dc bus voltage back upstream into the phase converter. Normally a utility 3 phase supply grid would happily accept this charge but not in my situation.

    Is there anyone with knowledge of the machine/ SDU600-w driver who has modded to allow a slower decel rate ? I am aware that I could g code the problem away by creating a macro involving dwell to step reduce the ramp rate but I would prefer to do something off the driver board. Maybe bring in to play a switch/ resistors to dump the excess voltage as regenerative braking won’t suffice. Thanks Phil
    Sounds like you have a problem with the Braking Resistor or the lack of one this should take the load from the spindle motor stopping

    So see if it has one or if you can fit one this will solve you problem if you can
    Mactec54

  4. #4
    Member
    Join Date
    Jan 2005
    Posts
    11408

    Re: Controlling/adjusting spindle decel ramp speed Okuma LC20

    Quote Originally Posted by Tarakai View Post
    Hi All
    I have an Okuma LC20 being run off a rotary phase converter (8kw) with a large 30 hp idler motor in parallel. Being in country Australia the supply is 230v single phase with no 3 phase available. I have added the 30 hp idler as it supplies the extra grunt to accelerate the DC spindle without any loss of phase errors occurring. My problem is that I have overvoltage error anytime I stop/slow the spindle from a speed greater than 100 rpm. I am sure this is happening because the SDU600-w driver tries to feed the excess dc bus voltage back upstream into the phase converter. Normally a utility 3 phase supply grid would happily accept this charge but not in my situation.

    Is there anyone with knowledge of the machine/ SDU600-w driver who has modded to allow a slower decel rate ? I am aware that I could g code the problem away by creating a macro involving dwell to step reduce the ramp rate but I would prefer to do something off the driver board. Maybe bring in to play a switch/ resistors to dump the excess voltage as regenerative braking won’t suffice. Thanks Phil
    The Braking Resisters or Regen are bolted to the drive board in the Dc unit these are most likely burnt up they had a problem with these over heating with to many stop / starts
    Mactec54

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