Repost: UV Amplifier (it's about 3-phase BLDC motor, not ultra violet)

Discussion in 'General Electronics Chat' started by wxf, Jan 13, 2014.

  1. wxf

    Thread Starter New Member

    Jan 13, 2014
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    0
    Hi,

    I'm building a motor stage for university project. It took me a while to realize that what I needed is a what's called UV amplifier.

    I Googled on this but were only able to find some very limited info:
    ideas/concepts:
    http://www.electromate.com/db_suppor...Amplifiers.pdf
    product:
    http://www.motioncontrol.com/node/7125

    Basically I have a motion control card with a pair of A/B phase output. It is already with commutation but I will need to lead them towards the amplifier to output 3 phase current to drive a BLDC motor.

    I'd like to build it myself, but it looks like even if I want to buy there isn't much available on the market. It could be that I have not looked hard enough, but the one listed above is a PWM output stage. I'm looking for a linear stage.

    So in summary, I'd like someone to get me started on this project. The requirement is 1) an amplifier that takes a pair of phase input with commutation; 2) output to drive a 3-phase BLDC motor; 3) the amplifier has to be analog, not PWM.

    Thanks in advance,

    Jay
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,507
    2,367
    You did not say if you want open or closed loop control?
    BLDC or AC sinusoidal?
    The AC type with sinusoidal control is the simplest drive you can get but, but harder to control.
    The sinusoidal drive usually has the U V phase fed as control with the third W phase extrapolated from the UV pair.
    If you want analogue control of a BLDC motor there are many A-M-C drives with ±10vdc analogue input available surplus.
    BTW, although AC sinusoidal motor and BLDC are practically identical in design, they are dissimilar in how the stator is fed, AC sinusoidal is 3ph AC and with BLDC, only two windings are fed at any one time.
    You need to confirm the motor you have, the difference is in the commutation feedback device or method.
    Max.
     
  3. wxf

    Thread Starter New Member

    Jan 13, 2014
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    0
    It should be just a straight amplifier. The closed loop will go through the controller via an installed encoder.

    It is BLDC. And thanks for explaining the difference between AC & BLDC. I'd like to figure out a circuit that can extrapolate the W phase as you wrote. I just looked up the AMC web page. (thanks) The problem with the AMC is that, the one with the analog output only works with a minimum voltage of 20Vdc. I'm hoping the circuit should be straightforward to understand and tune. But for now, I can't find any reference on it and don't know how to search it. There seem to be quite a bit of mfg that makes 3-phase drive ICs. Don't know if they might help.

    Thanks,

    Jay
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,507
    2,367
    Still not sure of your requirements and what you already have in the way of motor and/or drive/controller?
    When we talk driving signal there is the nature of the drive input signal and motor output power signal.
    If using a BLDC motor, it can be controlled with a 3phase sinusoidal signal instead of typical 2ph BLDC to the motor, but if you intend using a UV input command signal, these have to be 120° apart and the phase angle must correspond to the position of the rotor, detected by a feedback element of some kind.
    Also the drive output is generally a 3ph varying frequency for rpm and PWM sine wave modulation for current.
    By analogue, do you mean pure 3ph variable frequency AC sine wave with varying amplitude?
    Max.
     
  5. wxf

    Thread Starter New Member

    Jan 13, 2014
    8
    0
    Max,

    "Still not sure of your requirements"

    I'd like to figure out a circuit that can extrapolate the W phase. That is, how I get from the UV input signal, the signal for U, V, & W.

    "and what you already have in the way of motor and/or drive/controller?"

    I have a BLDC motor that takes the UVW 3 phase current. It has a rotary encoder. I also have a controller that reads the encoder, performs the commutation, and outputs U&V signal.

    So hope this is clear enough for you to help me. :)

    "but if you intend using a UV input command signal, these have to be 120° apart"

    As I explained, this is performed by the controller.

    "By analogue, do you mean pure 3ph variable frequency AC sine wave with varying amplitude?"

    Yes, as opposed to PWM output.

    Thanks,

    Jay
     
  6. wxf

    Thread Starter New Member

    Jan 13, 2014
    8
    0
    I know this is a bit uncommon subject. So any help will be greatly appreciated.

    Jay
     
  7. wxf

    Thread Starter New Member

    Jan 13, 2014
    8
    0
    This thread is sinking very fast to the bottom. :( Last attempt to ask for help!
     
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