What is the theoretical energy product limit for permanent magnet materials?
Maximum energy product is found by multiplying the values of Bd and Hd at points along the 2nd quadrant BH curve; BHmax is the highest value reached. The unit is mega-gauss-oersteds [MGOe], so you move the decimal point 6 places to the left in the answer. As you move along the second quadrant curve, the value of Bd increases while the value of Hd decreases, and visa versa. Because the curve for rare earth materials is close to a straight line, the maximum energy product (BHmax) will be found close to the middle of the curve, where the values of Bd and Hd are almost the same, i.e., where Bd = Br/2 and Hd = Hc/2. A line drawn from this point on the BH curve to where B and H are zero represents the optimum load line (PC) slope for the material. The value of the slope of this load line, or permeance coefficient, is close to 1.0, but it is usually more cost efficient to cause the magnet to work at a higher PC in its final magnetic circuit. Now, the value of Hc can mathematically never be gr
