0195136047.pdf

474 MAGNETIC CIRCUITS AND TRANSFORMERS

B,T

H,At/m

0

−0.2

−0.4

−0.6

−0.8

−1.0

0.6

0.4

1.0

0.8

0.2

− 250 − 200 −1 00 − 50 50 100 150 200 250

Figure 11.1.3Typical hysteresis loop of a magnetic-core material.

Flux φ

Core

I

Figure 11.1.4Part of a laminated core.

magnetic material to the total (gross) volume of the core is known as thestacking factor.The

thinner the lamination thickness, the lower the stacking factor. This factor usually ranges between

0.5 and 0.95.

EXAMPLE 11.1.1

(a) Estimate the hysteresis loss at 60 Hz for a toroidal (doughnut-shaped) core of 300-mm

mean diameter and a square cross section of 50 mm by 50 mm. The symmetrical hysteresis

loop for the electric sheet steel (of which the torus is made) is given in Figure 11.1.3.

(b) Now suppose that all the linear dimensions of the core are doubled. How will the hysteresis

loss differ?