Solenoid operation

Discussion in 'General Electronics Chat' started by ECM, Jan 7, 2009.

  1. ECM

    Thread Starter New Member

    Jan 3, 2009
    Just wondering if you guys could give me some theory as to the operation of a solenoid.

    Dealing with 24Vac irrigation solenoids, and long runs of wire we deal with some different siturations.

    From what I understand. Voltage and current are proportional to each other when it comes to inductors. If voltage goes up so does current, and if voltage goes down so does current. Opposite from what ohms law states dealing with resistance.

    Now if you were to drop the voltage to some dangerously low level, you will no doubt lose electro-magnetic energy, but if the voltage is not low enough to keep the solenoid from closing, how would that affect the solenoid? Would it heat up even though there is less current? Or do something else?

    From my understand that if the solenoid plunger did not move and close the air gap the current would stay higher than if the plunger did move. Perhaps not as high as the initial inrush current would be, but higher than the holding current would have been. Is this true?

    Thanks for any help.
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    Not exactly.

    The magnetic field generated is proportional to the change in current, or more specifically the time rate of change.

    The magnetic field acts on the mechanical plunger to move it when the current changes rapidly. This occurs at switch on or off.

    The plunger usually acts against a mechanical return spring, although it is quite possible to construct a solenoid to fire in either direction.