Simple Basic Electronics question...I hope

Discussion in 'Bob & Don's Electronics Forum' started by Mike Stoner, Dec 3, 2015.

  1. Mike Stoner

    Mike Stoner New Member

    Joined:
    Dec 3, 2015
    Location:
    Rapid City, South Dakota
    Ok simple its not because Ive been searching for answers all over the internet. I have a valid piece of OOC equipment related to this but the question is basic electronics.
    The question is on an AC electromagnetic coil hooked to 120V AC if you supply power to one end and a neutral to the other you are in fact shorting that AC to neutral or ground in order to generate current flow. Is the inductance created by the flow of current through the coil enough resistance to prevent a direct short to ground or will this trip the breaker? Does there not need to be some kind of load in this crkt to prevent a direct short or is the coil enough of a load?

    With an AC electromagnet....in this case a magnetic coil that actuates a plunger that releases a brake so a motor can turn. It is a three phase 480 volt motor. I realize that to create magnetic force current must flow through a coil. If I have 4 terminals on this coil, and two wires coming from the motor (2 240 volt phase legs making the 480 volt power to the coil on the terminals 1 and 2 and terminals 3 and 4 are wire nutted together, How can this possibly work with no possible current flowing through it. I am thinking I need to ground the center two terminals to produce current flow however 480 to ground is a direct short unless the coil itself will limit current flow via inductance..... If you can shed any light on this I would be forever in your debt.
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    The coil has a reactance together with the resistance of the coil. Together they give an impedance -- like what resistance is to DC-- which limits the current flow when a voltage is placed across the coil.
    http://www.electronics-tutorials.ws/inductor/ac-inductors.html gets it at a moderate level.

    Without getting into your circuit specifically, I suspect that your 3-phase electromagnet assembly will work the same whether you hook the middle to a neutral or not. I have no experience with 3-phase electromagnets. However balanced (symetric) 3 phase loads normally would work the same whether the junction point of the Y is connected to anything or not.
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. Mike Stoner

    Mike Stoner New Member

    Joined:
    Dec 3, 2015
    Location:
    Rapid City, South Dakota
    [QUOTE="Without getting into your circuit specifically, I suspect that your 3-phase electromagnet assembly will work the same whether you hook the middle to a neutral or not. I have no experience with 3-phase electromagnets. However balanced (symetric) 3 phase loads normally would work the same whether the junction point of the Y is connected to anything or not.[/QUOTE]

    Technically it is not a 3 phase electromagnet. Its really two separate 240V AC electromagnetic coils wound around the same core. So the basic principles of AC current should apply. Terminals 1 and 3 are one wire and terminals 2 and 4 are the other. But to make matters more complicated the coil is open so even if there is a valid path for AC it still would not work, but I am replacing the coil and cant seem to figure out how it would work anyway
     
  5. Mike Stoner

    Mike Stoner New Member

    Joined:
    Dec 3, 2015
    Location:
    Rapid City, South Dakota

    Ok, That tutorial is pretty much what I was hopping but I could not remember. Technically the coil itself will limit flow to ground due to the inductance created by it, That should be enough of a load to prevent shorting to ground....I think my problem may lie in the fact that the terminal 3 and 4 need to be grounded in order to produce current flow through the coil
     
  6. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Ahh... Probably the two wire coils get connected in series or parallel-- depending on the voltage. It is important to get the phasing right. If you get the phasing wrong, you will probably produce smoke.

    I made a schematic. I understand that the coils are actually intermixed on the real solenoid. If the solenoid was 120/240 VAC, you would wire like the red wires for 240 and like the blue wires for 120. Label the 1, 2, 3 and 4 terminal numbers to match your needs. The black dots indicates the polarity of each coil.
     

    Attached Files:

    Last edited: Dec 3, 2015
  7. DonL

    DonL Jack of all trades Master of one

    Joined:
    Mar 30, 2011
    Occupation:
    Rocket Scientist
    Location:
    Houston, TX
    What is the "OOC equipment" that you have ?

    Sounds like you need to hook your coils up in series. If they only have one winding per core, phase does not mater.

    Good luck. Be safe, use a fuse and PPE.
     
  8. DonL

    DonL Jack of all trades Master of one

    Joined:
    Mar 30, 2011
    Occupation:
    Rocket Scientist
    Location:
    Houston, TX
    That would be nice.

    But I like guessing, and reading minds. :D
     

Share This Page