using only 3 phase AC source device, explain how to control the speed of dc motor

Replies

• 

  narayana murthy

  by changing phases you can control about direction well coming to speed control it can done by voltage control method or any other
• 

  lal

  By using different combination of phases, different voltages can be obtained. Like any phase and neutral, any two phases. But still the possibility of voltage variation is limited to certain specific values. Its not a wide range!
  And, the DC motor will be running on DC supply, right? So wont there be a AC to DC converter?
• 

  everett.pattison

  What are some more details on your project? Are you allowed to rectify the AC to a DC voltage?
• 

  PraveenKumar Purushothaman

  A DC Motor won't run in an AC Source. It is better to use Bridge Rectifier, which is used to rectify both the polarities, thereby dynamically changing the polarity will make the DC Motor run in both directions. 😀
• 

  praba230890

  Don't make this so hard. It's so easy we have SCR's which always give it's presence when we looking for speed control of any motor. Just pick the control method that is suitable for the load(motor) may be voltage control or frequency control or any other control. Now put the Rectifier which acts as converter then the converted D.C is given to the load through SCR unit which is called as power conditioning circuit. By properly triggering the SCR'S in the conditioning ckt using feedback control you can fine tune the speed now.
• 

  PraveenKumar Purushothaman

  BR is better than SCR as it provides both the polarities and a polarity change right?
• 

  freak16

  3 phase Bridge rectifier can use both diodes and SCR.
  There can be no comparison between BR and SCR.
  As SCR is a power electronic device and BR is the place where we use it.
• 

  praba230890

  I wanna make it clear again we got to use both BR and SCR here BR acts as converter and SCR acts as power conditioner(which changes the input voltage or frequency to control the speed) as i said in my previous post...
• 

  Arp

  method listed above are used only for load torque in positive direction and braking only with reverse speed.
  to control the speed from 0 to rated in both direction and allowing it to support load torque also so that motor can run in any direction we should have four quad operation possible.
  first if it is a separately excited machine then u can use three phase bridge rectifier having scr in armature circuit and a dc source in field ckt with reverse switch (cheap i suppose). or for shunt motor(generally used) ypu can use reversible switch across armature terminals also.
  or you can use dual converter or first rectifier then its output to four quadrant chopper(type-e).
• 

  praba230890

  Yeah you are right Arp....if we want four quadrant operation then we need to use 3 phase dual converter drives to drive the motor. In this method we need to connect two scr units are to be connected with the armature but in opposite directions.
  
  

  Arp

  method listed above are used only for load torque in positive direction and braking only with reverse speed.
  to control the speed from 0 to rated in both direction and allowing it to support load torque also so that motor can run in any direction we should have four quad operation possible.
  first if it is a separately excited machine then u can use three phase bridge rectifier having scr in armature circuit and a dc source in field ckt with reverse switch (cheap i suppose). or for shunt motor(generally used) ypu can use reversible switch across armature terminals also.
  or you can use dual converter or first rectifier then its output to four quadrant chopper(type-e).