Question on PMSM motor driver

Discussion in 'General Electronics Chat' started by daug, Mar 30, 2009.

  1. daug

    Thread Starter New Member

    Mar 30, 2009
    3
    0
    When a sine wave of current is applied to a PMSM motor, I do not much understand how the current flow. Picture1 is the schematic(page 19). Picture 2 shows the sample voltage on the shunt resistor(R5),channel 1 . We can see the positive and nagetive half wave.

    My question is , when the lower MOS swtich is on, there is positive voltage on the shunt resistor, but how the negative wave comes? By the freewheeling current flow through the built-in diode in the MOSFET?
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    I ripped out the schematic images. I don't understand your question.

    Are you wondering how the negative part of the cycle is driven? On the right half of the top schematic are Three Half H-Bridge Drivers, one for each phase.

    Power Circuit:
    [​IMG]

    Control Circuit:
    [​IMG]
     
  3. daug

    Thread Starter New Member

    Mar 30, 2009
    3
    0
    I have got it! The control signal PWM , there is a momemt the lower MOS is on and 3 higher MOS are off, there are freewheeling current. I attach the waveforms. I am a rookie, hope any one here who is interested in PMSM control can discuss with me in future.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
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    You might want to add a second very fast recovery diode across the MOSFET assist in killing those spikes. The body diode doesn't seem to be speedy enough.

    P.S. Nice scopes! The one on the right looks familiar, except the language, of course. :)
     
  5. yscheok

    New Member

    Jun 13, 2009
    1
    0
    Hi all,

    currently i try to setup hardware of motor drive for the PMSM. but i facing problem to drive the motor. attachment is my connection circuit.

    1.When dc link is on, i switch on the S1 & S4, the rest switch is off. there is no voltage at the R1, itz because of the too low resistance and act as short circuit? (it causing my IGBT module burned) :(

    2.But when i remove the motor and put a resistance load, when switch on the S1 and S4, there is a voltage drop on the resistance when measure with multimeter. that mean my switching is no problem.

    where is my mistake to when operating the PMSM motor? :confused: can you all give me some advise?
     
  6. cachapo

    Member

    Aug 24, 2009
    12
    0
    Hi everybody,

    I´ve got a PMSM running, and I´ve noticed something strange...

    The current that I´m reading in one of the phases of the motor is much higher than the current that I read in the power supply. Does anybody know why?

    Thanks.
     
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