Q3Electrical Materials
Question
Q.3. Show the total stored magnetic energy in a permanent magnet on its B-H loop.
Answer
The stored energy of a permanent magnet appears in the second (demagnetization) quadrant of its B-H loop; at any operating point the stored/available energy density corresponds to the B×H rectangle area, maximized at the (BH)max point.
The total stored magnetic energy of a permanent magnet is represented on its B-H loop in the second (demagnetization) quadrant — the portion of the loop between the remanence point Br on the +B axis and the coercivity point Hc on the −H axis, where a permanent magnet actually operates. At any operating point (H, B) on this curve, the energy density available to an external magnetic circuit corresponds to the area of the rectangle B×H drawn from the origin to that point; this product is zero at both Br and Hc and passes through a maximum, (BH)max, at an intermediate point — the maximum energy product that serves as the figure of merit of permanent-magnet materials.