BLDC Motor, voltage pumping due to braking or reversing

Discussion in 'Power Electronics' started by riscy00, Aug 22, 2016.

  1. riscy00

    Thread Starter New Member

    Jun 23, 2010
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    0
    I have 50W 4 pole BLDC Motor as used for servo acuator (or CNC) with screw.

    I have 3 phase generator and 6 rectifier diode with provide 48V under steady rpm.

    I wish to calculate sizing of the capacitor in case of motor slow down (reversing torque) or estabishing braking. Is there guideline to do that. The cap sizing is critual due to space constraints.

    I know that current pumping into generator is impossible due to rectifier diode which work only for forward current, so capacitor bank play important role to limits voltage from approaching breakdown area.
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Welcome to AAC!
    Which capacitor are you talking about?
    A schematic would help us to help you.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If CNC you should obviously have a suitable BLDC drive, what make of motor. drive and type of present DC supply?
    If you have a 3 phase rectified supply you should already have a large capacitor for the drive?
    Max.
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,142
    1,790
    I don't think you can make a successful servo drive with the listed components. A BLDC motor will not move just because you connect it in some fashion to a power source. Doing this without knowing what you are doing could have disastrous consequences including serious injury or death.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Also that is a very small motor for typical CNC purposes, the ripple on a 48v full wave rectified supply is <5%, so a smoothing capacitor size would be relatively trivial.
    The drive should take care of the concerns you have in the OP.
    Max.
     
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