Magnetisation

Question 1

Why does Hysteresis Occur

Answer 1

Hysteresis occurs because work must be done every time the magnetic domains within the steel laminations are reversed.

Question 2

Why do eddy currents occur

Answer 2

Alternating magnetic fields cause alternating electric fields,
An electric field in the presence of a conductor will cause current to flow, which in turn causes power losses in the form of unwanted heat

Question 3

Characteristics of Pm materials

Answer 3

When the applied field is removed from a soft magnetic material the flux density reverts to zero.
For a PM material, this does not happen, and the flux density reduces to a level known as the remanent flux density
If a magnetic field is then applied in the opposite direction in order to reduce the PM flux density to zero, the required field is Hc , known as the coercive field intensity.
PM operate in 2nd qudrant
BHmax is a measure of how hard magnet is working to deliver magnetic stored energy to external magnetic circuit
The greater it is the greater the ability to deliver magnetic energy to external magnetic circuit

Question 4

What are iron losses

Answer 4

Power losses due to laminations of electical machines, owing to two main mechanisms

Eddy currents
Hysterisis