Fig. 1 shows the core of a simple DC motor. The magnetization curve for the metal in this core is given by Fig.2(a) and (b) Assume that the cross-sectional area of each air gap is 18 cm2 and that the width of each air gap is 0.05 cm. The effective diameter of the rotor core is 4 cm.

a. It is desired to build a machine with as great a flux density as possible while avoiding excessive saturation in the core. What would be a reasonable maximum flux density for this core?
b. What would be the total flux in the core at the flux density part (a)?
c. The maximum possible field current for this machine is 1 A. Select a reasonable number of turns of wire to provide the desired flux density while not exceeding the maximum available current.

N=? = 48 cm - N turns 4 cm 4 cm Depth = 4 cm 1,=4 cm lg = 0.05 cm 4 cm Fig. 1 Primitive DC motor structure