## Magnetic Flux

## Magnetic Flux

(OP)

I have drawings of magnets with physical dimensions, materials, tolerances, etc. How do I add a Magnetic Flux requirement (weber, volt second) so I can measure the magnet when is arrives and be sure that it is fully magnetized? I know how to add this to the drawing literally however where do I get the characteristics and tolerance for this? Should the magnet supplier give this information? Is there a way to calculate this value based on the material data sheet that is typically used with BH curves and other characteristics (see attached file)?

I have a Helmholtz coil and flux meter and I would like to make sure that the magnets are fully magnetized and are the right material.

I have a Helmholtz coil and flux meter and I would like to make sure that the magnets are fully magnetized and are the right material.

Clyde Hancock

Design & analysis of electric motors and generators

www.motorconsultants.com

## RE: Magnetic Flux

The units for magnetic moment are Volt-Second-Meter, Weber-Meter or Ampere-Meter²

Most magnetic modeling software packages have the capability of directly calculating the value for you. The equation for it is pretty simple though:

If your magnet dimensions are inches:

(Volume)*(2.54³)*(Br)*((Permeance coefficient + 1)/(Permeance coefficient + Recoil permeability))/100,000

If your magnet dimensions are millimeters:

(Volume)*(0.1³)*(Br)*((Permeance coefficient + 1)/(Permeance coefficient + Recoil permeability))/100,000

Br (remanence) should be Gauss.

The calculated value for both equations will have units of milliWeber-centimeter (mWbcm)

When I need to calculate Min/Max limits for a particular magnet part:

For minimum value: Model the part at minimum material condition and minimum Br

For maximum value: Model the part at maximum material condition and maximum Br

To be honest, most of the time I just need to calculate the minimum value.

## RE: Magnetic Flux

Thanks!

Clyde Hancock

Design & analysis of electric motors and generators

www.motorconsultants.com

## RE: Magnetic Flux

But then would test the first 50pcs or so in the HH coil and set the highest and lowest aside.

Then we would take a couple from each of these groups and actually run full testing on them.

This was to give us more confidence in setting a test min.

After all even if you 100% test there will be some that are out of range, it is all statistics.

Sometimes we would find undersaturation, but usually it spoke to a dimensional issue.

= = = = = = = = = = = = = = = = = = = =

P.E. Metallurgy, consulting work welcomed

## RE: Magnetic Flux

Clyde Hancock

Design & analysis of electric motors and generators

www.motorconsultants.com

## RE: Magnetic Flux

using HH coils, or a single search coil, you test moment for a fully open circuit, and so moment / volume = Bdi (intrinsic flux density). if recoil permeability = 1, e.g. Bd = Hd (in a perfect square loop), then Bdi = Br. In theory, Bdi<=Br.

## RE: Magnetic Flux