AC through DC solenoid

Discussion in 'General Electronics Chat' started by Rustifer, Dec 16, 2009.

  1. Rustifer

    Thread Starter New Member

    Dec 15, 2009
    Using a small pull solenoid, 24VDC, 30 ohms. Could I use 24VAC for this ?
    What is the difference between a DC coil and an AC coil of the same rating ?
    What is the result of using AC for a DC coil and vice versa ?
    Assuming 50% duty cycle.
  2. Duane P Wetick

    Senior Member

    Apr 23, 2009
    You probably will not be able to generate enough magnetizing force to pull in the plunger with AC. Now add a Full wave bridge rectifier and a 500 mf capacitor to + and - and see the difference. Also, the holding current is much less than the step pull-in current.

    Cheers, DPW [ Spent years making heaters out of op-amps.]
  3. k7elp60

    AAC Fanatic!

    Nov 4, 2008
    Ac coils for relays and soleniods have a shader ring(usually made of copper)on the top of the core. Because of the shader ring, the magnetism developed in part of the core lags somwhat the magnetism of the remainder of the core. That is, there is a slight phase displacement between the magnetism of the part of the core and the remainder of the core. Thus, as the unshaded-core magnetic energy decrease to zero every half-cycle, the magnetic energy still present in the shaded portion of the core holds the armature sealed. By the time the energy in the shaded portion decrease to zero, coil and unshaded-core magnetic energy have begun to increase once again as current increase in value.

    Applying AC to a dc coil will cause the coil to hum and if it is a relay it will chatter. The resistance of a DC coil is about 4 times the resistance for an AC coil for the same voltage.

    AC coils have inductive reactance in addition to the coil resistance that affects the coil current. The AC current for a 24V AC coil is about double the DC current for a 24V DC coil.

    Operating a 24V AC coil on 24V DC could cause the coil to fail as the current would be too great. The current would be very close to 4 times the current for 24V DC coil.
    cmartinez likes this.
  4. Rustifer

    Thread Starter New Member

    Dec 15, 2009
    Couldn't have asked for better explanations !
    Thank you both very much.
    I have a much better understanding now.
    Happy Holidays