motor control questions

Discussion in 'The Projects Forum' started by mobydick, Nov 4, 2012.

  1. mobydick

    Thread Starter New Member

    Nov 19, 2010
    27
    1
    hello,i have purchased a cheap dc motor with controller (which is not working) from an old treadmill hoping to make my own controller.
    the motor is 3hp rated for 180V DC
    i tried to track the original controller to see how it worked.
    partially finished schematic included.
    i noticed that the controller used the rectified 220VAC directly to drive the motor(308v dc!!)
    my questions is :
    1-is it ok to drive 180V dc motor from 308V dc?
    2-what is the difference between pwm drive and scr based driver and which is suitable more in recent case?
    3-is it convenient to use adjustable buck converter to drive this motor?
     
  2. mobydick

    Thread Starter New Member

    Nov 19, 2010
    27
    1
    any suggestions?
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,036
    This is a mains-direct application and I believe this is not an allowed topic here, for safety reasons. Not sure if repair of a commercial device falls under this rule, though.
     
  4. mobydick

    Thread Starter New Member

    Nov 19, 2010
    27
    1
    no i donot want to repair it
    i just want to understand how 180v motor could run at 308v?
     
  5. mobydick

    Thread Starter New Member

    Nov 19, 2010
    27
    1
    do you mean in project forum?
    i have seen lots of project like that but not sure in project forum or another forum
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    The motor can "run at 308v" because the circuit uses PWM to apply power to the motor in short pulses, and since power is on/off for set a percentage of time it averages out to a lower voltage to the motor.

    The circuit used in the mains powered speed controller you have is quite dangerous (as Wayneh said!) and it is not advisiable for you to experiment with dangerous mains powered equipment when you don't have a good understanding of the equipment and the safety issues.

    Maybe you should post a new thread; "I have a 180v 3hp DC motor, how can I safely make my own controller?"
     
    mobydick likes this.
  7. mobydick

    Thread Starter New Member

    Nov 19, 2010
    27
    1
    thanks "the_RB"
    i'll post new thread
     
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