Why does undervoltage create heat in machinery?

Discussion in 'General Electronics Chat' started by foolios, Dec 6, 2009.

  1. foolios

    Thread Starter Active Member

    Feb 4, 2009
    160
    1
    I am reading that not having machinery run undervoltage creates heat and damage to machinery.

    Why does not having enough voltage create heat?

    What kind of damage occurs when machinery doesn't have enough voltage?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Power is the product of voltage and current. Less voltage means more current to produce that level of power. Conductors are generally sized for the designed level of current, so they overheat when asked to carry more.
     
  3. foolios

    Thread Starter Active Member

    Feb 4, 2009
    160
    1
    How does the machinery draw more current than the voltage is pushing?
     
  4. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    When operating at the proper voltage and current, the right amount of torque is produced and proper speed is maintained. When voltage is reduced, torque is reduced and therefore the amount of slip in the motor is increased resulting in lower speed. Since the speed is reduced, back EMF is also reduced causing higher current than normal. It is like trying to run a 4 cyl gasoline engine on 3 cyls. It is just harder on the engine.
     
  5. darenw5

    Active Member

    Feb 2, 2008
    45
    0
    According to what I've heard, at least for certain kinds of machines, the lower voltage results in the slower speed, and that means less cooling by air of moving coils, which can then overheat.
     
  6. foolios

    Thread Starter Active Member

    Feb 4, 2009
    160
    1
    Thanks a lot for the explanations. Fascinating stuff!
     
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