Electromagnet Question

[gyulasun]

How much power is required to break the attraction of the perminant magnet to the electromagnet core?  How is the power of the electromagnet related to the strength/size of the perminant magnet? 

Hi Mondrasek,

Would you answer this:  Do you wish to utilize the natural attraction of your permanent magnet to the core of the electromagnet before you want to switch the electromagnet on or it is not needed for you?

Thanks,  Gyula

[mondrasek]

@mscoffman  Wow, great answer!  A lot for me to digest in that.  I look forward to your future posts.

@Gyula  I don't believe there is a need for the attraction.  I believe it could possibly help to an extent, but also the perminant and electromagnet will never actually come into contact.

The idea here is to use pulsed electromagnets as the stators in the patent design.  If the electromagnet stators can be pulsed and fire the mass switch magnets instead of perminant magnet stators there would be no approach wall that creates a negative torque.  If the BEMF can be captured when the electromagnet is turned off (ala Bendini) then the only power needed to fire the mass switch (minus losses) is that of energizing the electromagnetic field.

I am trying to understand if the mass switch perminant magnet will fire to it's maximum height due to the energy of the electromagnet current AND the perminant magnet's force.  If the resulting PE of the raised magnet is equal or less than the energy used to energize the electromagnet this is also a loss.  If the PE is greater (due to the perminant magnet field) then we have captured that energy.

Thanks again for the great input.

M.

[0c]

@mscoffman,

using electromagnets instead of permanent magnets would be really convenient for prototyping and testing. However, sometimes it can be much more difficult to actually construct a device. I challenge you to design an electromagnetic WhipMag. I'm sure we could learn a lot from it.

OC

[Xaverius]

Thanks guys.  Good info.

So, say one is to take a cylindrical electromagnet with opposite pole configuration.  Set it with the North pole facing up and uncharged.  Place a perminant magnet on top so that it's North pole is down and it is in contact with and in attraction to the ferous core of the electromagnet.  When you apply an electric source to the electromagnet it should repel the perminant magnet.

How much power is required to break the attraction of the perminant magnet to the electromagnet core?  How is the power of the electromagnet related to the strength/size of the perminant magnet? 

If two perminant magnets are forced together in a vertical arrangment so as to repel, and then the top magnet is released, it will accelerate upwards to a height much greater than where it will eventually settle and hover over the bottom magnet.  Can the electromagnet/perminant magnet arrangement be made to act the same?  What is the relationship of the power consumed by the electromagnet to the strength/size of the perminant magnet to create this equal opposing force?  Does the fact that we must first break the attraction require more power to the electromagnet than if there was not the attraction?  Does the acceleration of the perminant magnet away require more power to the electromagnet due to the fact that the perminant magnet is moving through the electromagnet field?  Or will the electromagnet field generate outwords from the center of it's core and drive the perminant magnet away so that the two fields never overlap?

Thanks again for your input.

M.

Hi, ceramic permanent magnets have a magnetic flux density of  approximately .5 Tesla, neodymium magnets have a magnetic flux density of 1 Tesla and more.  Assuming your using neodymium(the overunity builders material of choice) then your solenoid/inductor/electromagnet would need the same magnetic flux density, 1 Tesla.  Anything less and the solenoid/permanent magnet may attract even when opposite poles are together.

Ordinary unpurified iron such as found in fasteners(nails, screws, and bolts)  has a relative permeabilty of at least 50.  The formula for magnetic flux density is

Ampere-Turns/length of the core material X ur

Turns=number of turns of wire
length=measured in meters
u=permeabilty of free space/air/vacuum  4pi x 10^-7
r=relative permeability

If you are using a nail or bolt that is .1 meters long for your core material (about 4 inches) with diameter of .01 meters(about .4 inches), the cross-sectional area of the bolt/nail would be .00007854.

For iron, r=50.  r X u =.00006283.  1 Tesla divided by .00006283 is approximately 16000 Ampere-Turns/meter.  16000 X .1 meters(length of the core) is 1600 Ampere-Turns. If the coil resistance is 10 ohms and you wish to use 1 Amperes then you'll need 10 Volts.  With 1 amperes you'll need 1600 turns of wire.(1 Amperes X 1600 Turns = 1600 Ampere-Turns).

The power consumption for the coil would be 10 Volts X 1 Ampere = 10 Watts.
At repulsion when the electromagnet is energized, force is calculated like this:

F=B^2A/2u

B=Total Tesla which in this case is 1(electromagnet) + 1(permanent magnet) =2
A=in this case .00007854
u=4pi X 10^-7

F=2^2(4) X .00007854/2 X 4pi X 10^-7=125 Newtons

Something else you have to consider is the pulse rate of your electromagnet, the faster it is switched off and on the higher the Reactance which is a form of electrical resistance.  So the higher the Reactance then the more Voltage needed to produce the necessary Coil power.  One way around this is to wind multiple coils around the core and wire them in parallel.  For example if you are using 100 feet of wire for your coil, you can divide it up in to 10 foot lengths. Wind each ten foot section individually one on top of the other and attach the ends of the wires together at each end.  This will reduce the Reactance and keep the required voltage from rising.  Hope this helps.

[mondrasek]

@ Xaverius.

Excellent.  That fills in a lot of the gaps in my knowledge. 

Very kind and generous of you to spell it all out.  I realy appreciate it.

Thanks again,

M.