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Trying to increase the magnetic flux density

  1. Jun 22, 2012 #1
    Hello all, long time follower, first time poster.

    (Also feel free to move this if it's not in the right section.)

    Basically I have this mechanism pictured here:

    You can imagine that the drawing is of a top view of a section cut of the total mechanism. This is the radius view, the full diameter would just be a mirrored image across the y-axis. Rough design is to use magnetorheological fluid as a frictional coupling device to open/close a gap located right on the other side of the disk. (Bottom view not pictured.)

    A recent problem is that when modeled to see what the magnetic flux density looks like, we get a lot of the field propagating around our mechanism instead of traveling through the mechanism. This is a very small, scaled design. For example, the total diameter of the rotating disk is about 30 mm. The MR fluid gap is around .8 mm. Pictured below is the current travel of the magnetic path. We can generate around 1.6 teslas through the mechanism which may be enough but we are trying to increase the density through the mechanism. Any tips or tricks are greatly appreciated.


    If any further information/clarity is needed, just let me know.


  2. jcsd
  3. Jun 23, 2012 #2
    I'm not sure exactly what you are trying to do, however here are some general comments:
    Magnets wound with tubing and water cooled can usually produce stronger magnetic fields than magnets wound with solid wire.
    The strongest magnets fields possible use coils that are wound with rectangular tubing, water cooled and have an air core. (These magnets are very power hungry)
    This question is probably not necessary, but have you checked the permeability and saturation flux density of the material you are using?
  4. Jun 24, 2012 #3
    Thanks for the reply man, and yeah I have checked the permeability of the material. The biggest problem is due to the mechanisms' thickness.

    The water cooling is a new concept to me, do you have a link to more information on the idea/how to make one?

    Thanks again.
  5. Jun 25, 2012 #4
    Have you checked saturation flux density?
    Saturation flux density is probably more important than permeabilty
    Google water cooled magnets.
    If you have other questions about water cooled magnets, post them here.
  6. Jun 25, 2012 #5
    What is the limiting factor when trying to go beyond 1.6 T ?

    Is it the current in the coil?
    Does the core saturate?

    Also the flux density through the disk is not uniform, is this of concerne?

    Calculate the reluctance in the core, air gap and disk to find what part limits the flux.
  7. Jun 25, 2012 #6
    We would like it to be more uniform SirAskalot throughout the entire radius of the disk.

    I will calculate some information and get back to you a little later, thanks.
  8. Jun 25, 2012 #7
    The biggest limiter to the flux is the air gap along with the actual encasement of the rotating disk. I need to optimize this.
  9. Jun 25, 2012 #8
    If the flux density keeps increasing as you increase the current, then there's not enough ampere turns. Increase the ampere turns by increasing the coil current or go to a water cooled coil. Or decrease the air gap.
    If the flux density stops increasing as you increase the current, then the magnetic material is saturating and you need to go to a material with high saturation flux density or a water cooled coil. A water cooled coil is bad news, requires lots of power.
  10. Jun 25, 2012 #9
    Okay, thanks for the input Carl, I will look towards acquiring different materials with higher saturation values.

    We want to keep power usage also at a low.
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