The demagnetization curve is the second quadrant of hysteresis loop, and we can get the main magnetics properties of magnet via demagnetization curve. The magnetization behavior of magnet can be shown by first quadrant of hysteresis loop. Different types of magnet have its own hysteresis loop and demagnetization curve.
H: The values of the eternal magnetic field strength H.
B: The values of the magnetic flux density B in the magnet and magnetic polarization J.
J curve: Show the contribution of magnetic material to the magnetic flux density, and depending on externally applied magnetic field strength.
B curve: Show the magnetic flux density B in the magnet, depending on externally applied magnetic field strength.
Initial magnetization curve: An initial curve shows the magnetic flux density, as a function of the externally applied magnetic field strength, for the initial magnetization of a magnet.
Br: Br it the remaining magnetization in a magnetic material when field strength H = 0 kA/m, after it has been magnetized to saturation in closed circuit.
Hcb: The coercivity is the magnetic field strength required to bring magnetic flux density back to 0 in ferromagnetic material which has been magnetized to saturation.
Hcj: The intrinsic coercivity is the magnetic field strength required to bring the polarization back to 0 in a ferromagnetic material which has been magnetized to saturation.
(BH)max: Energy Product, The total energy stored in a magnet (Br x Hc).
Hd: Hd is that value of H corresponding to the remanent induction Bd.
Operating load line: The operating load line describes the properties of the magnetic loop. Its angle depends on the magnet geometry and the magnetically soft pole pieces used. If a permanent magnet has no surrounding iron, the angle of the operating load line depends only on the magnet geometry. In systems with magnetically soft pole pieces, the angle of the operating load line depends on the relationship of the air gap to the magnet’s length. When an external magnetic field (H ≠ 0) is applied, the new operating load line is displaced parallel to the former one.
Operating point: The operating point is defined as the intersection of the operating load line and the B curve. It is the point on the demagnetization curve whose coordinates are the magnet’s magnetic flux density and the magnetic field strength in an operating state. The operating point of a permanent magnet must always be in the linear region of the demagnetization curve, taking the effects of temperature (temperature coefficients of Br and Hcj) and external opposing fields into account. If the operating point comes into the nonlinear region near the knee, the magnet will become partially demagnetized (irreversible losses).
Pc value: There are auxiliary lines for determining the operating load line of a disc magnet without surrounding iron. To construct the operating load line, connect the origin of the graph with the factor H/D. The factor H/D describes the ratio of the height to the diameter of the magnet. Note that the angle of the operating load line varies within a magnet; our figures show average values. For a very small H/D ratio (< 0.3) one should take into account that the operating point in the center of the magnet is much lower than the average value.
June 19, 2017
Are you into overunity permanent-magnet motor research?
June 26, 2017
Hi Simon, not overunity permanent magnet motor research.
June 20, 2017
H: The values of the eternal magnetic field strength H.
Eternal??? I guess external
June 26, 2017
Hello Adrian,
Yes, you’re right. It’s external. Typing mistake. Thank you!
This is Martin. I think I contacted you before when you worked for MAGTEC.
March 25, 2020
Olá Adrian, Rapaz, voce indicaria algum material para eu entender melhor a diferença entre as curvas de densidade de fluxo B e a curva J?
Sou mestrando de engenharia elétrica e vou desenvolver minha nesta área.
Obrigado e parabéns pelas publicações.
October 21, 2020
Dear Administrator
“H: The values of the eternal magnetic field strength H.”
There H is the value of the INTERNAL magnetic field. It real because a magnetic has been magnetized in closed magnet circuit. In this case the applied field is internal.
“B: The values of the magnetic flux density B in the magnet and magnetic polarization J.”
B is a magnet INDUCTION, not flux density. Flux density F=B*S.
“(BH)max: Energy Product, The total energy stored in a magnet (Br x Hc).”
It is true that (BH)max=Br*Hc/4
“Operating load line: The operating load line describes the properties of the magnetic loop.”
Operating load line das not describes ….
Initial Magnetization curve cannot have such kind, as shown in figure.
February 18, 2022
Анатолий. 1)Индукция это и есть плотность магнитного потока(не сам поток, который величина интегральная). 2)Здесь происходит машинный перевод с китайского. В китайском и японском “постоянный” пишется и имеет тот же смысл что и “вечный”. Просто машине такие детали не известны. А внутренние и внешние кривые построены на одном графике, их легко отличить по наклону.
February 18, 2022
3)линия нагрузки в замкнутой цепи примерно равна отношению источника поля к зазору. А для свободного магнита примерно равна отношению его длины к диаметру.
4)начальная кривая определяется кристаллической структурой. Она может быть очень разная. Хотя и есть определенные методы ее предсказания, или обратного синтеза гистерезиса через микромагнытный динамический анализ УЛЛ.