Motors and Magnetic Attraction

As the permeance of shell of motor is very low, magnetisation of shell is very weak.

A motor's ferromagnetic shell's magnetic field is not normal to the surface of the shell for permanent magnet or wound field DC motors, but it is in one direction only. Hold a magnetic compass near the outer surface, and I think you'll find that the needle will align itself with the direction of magnetic flux.

For AC motors, it varies as the frequency of the current, and it is also not normal to the outside surface of the shell.

I had a 1,200 lb pull magnet sent to me. The seller sent it in a cardboard box. The magnet was in the center of a block of foam. Around the foam (and between the outside of the box and the foam) he placed 6 sheet steel plates - one covering each side of the box and top & bottom.

The steel plates were enough to make the magnet shippable through normal mail.

The Ferrous material used in the Casing acts as magnetic shield and directs the lines of force back to the source, that being the field coils.

Sapper

Thanks a lot.......!!!