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A permanent magnet motor is a type of electric motor that uses permanent magnets for the field excitation and a wound armature. The permanent magnets can either be stationary or rotating; interior or exterior to the armature for a radial flux machine or layered with the armature for an axial flux topology.
The net magnetic moment of the magnet m therefore is =, where the triple integral denotes integration over the volume of the magnet. For uniform magnetization (where both the magnitude and the direction of M is the same for the entire magnet (such as a straight bar magnet) the last equation simplifies to: m = M V , {\displaystyle \mathbf {m ...
Depending on requirements, the orientation of the magnetic field may need to be changed 90 degrees to inspect for indications that cannot be detected from steps 3 to 5. The most common way to change magnetic field orientation is to use a "coil shot". In Fig 1 a 36-inch coil can be seen then steps 4, 5, and 6 are repeated.