Need Help , Motor Drive

Discussion in 'General Electronics Chat' started by yassser, Jul 25, 2011.

  1. yassser

    Thread Starter Member

    Jul 25, 2011
    91
    0
    Hi,

    I want to build a motor drive circuit for a 170V 30A motor to control its speed by a PWM signal from a microcontroller , I'm a student and I'm new to this , I was advised to use IR2110 with two n channel mosfets , this is the circuit available in the IR2110 application notes


    http://imageshack.us/photo/my-images/585/unled2is.jpg


    I'm actually a computer and systems student , Electronics isn't really my strength point . However , I understand the overall circuit idea.

    1st Question , Is this circuit the one I need?

    2nd Question , it is mentioned that this schematic is for a 100mH motor , I don't know if this is would work with my motor or will I have to change
    something.

    thanks in advance.
     
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    213
    1.) It looks like the circuit is for a synchronous AC motor. Is your motor an AC motor?

    2.) The capacitors may need to be changed to get optimal performance but otherwise it should be okay.
     
  3. yassser

    Thread Starter Member

    Jul 25, 2011
    91
    0
    thanks for your reply

    No it's a DC motor , I said I'm using PWM signal.

    would that be OK.
     
  4. tom66

    Senior Member

    May 9, 2009
    2,613
    213
    In which case I'd say it's unlikely that circuit will work.

    Capacitors block DC and pass AC. So they would allow for the motor to move for a bit but it would stop quickly. To make it work, the fets would need to be turned on and off rapidly, so the caps would pass AC, but then the motor would just move backwards and forwards a few degrees around a single position.

    Also, if it doesn't go without saying, be careful around 160-170V DC! That's more than enough to seriously injure or even kill someone.

    Do you need to be able to reverse your motor?
     
    Last edited: Jul 25, 2011
  5. yassser

    Thread Starter Member

    Jul 25, 2011
    91
    0
    -I thought those capacitors were just for filtering the noise , so what should I do to make it work on a DC motor , remove the capacitors?

    -Of course I will be very careful , thanks for your concern.

    -No I don't want to reverse the motor direction , I only want to control its speed .

    thanks again.
     
  6. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    In this case it's easy. Just connect one side of the motor to the middlepoint of the FETs the other side to + bus voltage. You actually don't even need the second FET (to the plus side, just a diode would be enough) but if you have two FETs you can use the second one for active braking.

    see the following excerpt from THIS site:

    "Half-Bridge DC Motor Drive

    [​IMG]
    A half-bridge is useful in applications that require unidirectional control with active braking. The half-bridge circuit may also be used to reduce the power losses for larger DC motors. The power losses in the upper power MOSFET may be much lower than using a Schottky diode. Half-bridge DC motor drives require Center-Aligned PWM with dead-time."
     
  7. yassser

    Thread Starter Member

    Jul 25, 2011
    91
    0
    thanks a lot , I'll give it a try.
     
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