It is desired to achieve a time-varying magnetic flux density in the air gap of the magnetic circuit of figure of the form Bg = B0 + B1 sin wt where B0 = 0.5 T and Bl = 0.25 T. The dc field B0 is to be created by a neodymium-iron-boron magnet, whereas the time-varying field is to be created by a time-varying current.

For Ag = 6 cm2, g = 0.4cm and N = 200 turns, find:

a. The magnet length d and the magnet area Am that will achieve the desired dc air-gap flux density and minimize the magnet volume.

b. The minimum and maximum values of the time-varying current required to achieve the desired time-varying air-gap flux density. Will this current vary sinusoidally intime?

Transcribed Image Text:

Area Am Alnico 5 Air gap area A N turns