constant torque

Discussion in 'General Electronics Chat' started by wes, Jan 5, 2008.

  1. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    are there any motors that are able to maintain a constant torque no matter the rpm . so say it runs at 5000 rpm no load and 5000 rpms under load because the torque doesnt decrease with speed increase or decrease and pulls the same amount of power
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Read up on pulse width modulation. That is the technique used to maintain nearly constant torque over the whole range of DC motor speed.

    AC motors can be controlled over a range of speeds with nearly constant torque using a variable frequency drive to essentially make a simulated AC waveform.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    Power output is defined as torque times rotational speed. Since input power is proportional to output power, then at fixed RPM, the input power will change as the load changes.
     
  4. h.d

    Active Member

    Oct 22, 2007
    150
    0
    you ask about motor with constant torque at variable speed or constant speed at variable torque?
    if you mean constant speed (5000rpm at noload and 5000 rpm at loaded)
    you should use syncronous motor which is AC-motor
     
  5. shankbond

    Active Member

    Nov 4, 2007
    53
    0
    my friend i believe that ,if there is load on synchronous motor then it draws more power,which is not desired .:rolleyes:
     
  6. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    I'm confused... Do you expect mechanical power for free? Of course the electrical power demand will increase! Synchronous AC motors do run at a fixed speed by design and will try its best to maintain it under load,.

    Steve
     
  7. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    alright thx for all the input
     
  8. Papabravo

    Expert

    Feb 24, 2006
    10,137
    1,786
    Every set of DC motor performance curves shows the torque going to zero at some speed. This is entirely different from the minimal torque required to keep a motor going at a constant speed within its range.
     
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