Hysteresis Loop Definition, Meaning, Types, Loss, BH Curve
Table of Contents
In a system that uses a magnetic field, hysteresis happens (Hysteresis Loop). Inherent in ferromagnetic materials is the phenomenon of hysteresis. Generally speaking, the hysteresis effect is what occurs when the magnetization of ferromagnetic materials lags behind the magnetic field.
What Is Hysteresis?
“Lagging” is what hysteresis means. Magnetic flux density (B) lags behind magnetic field strength (H) and is the defining feature of hysteresis. Hysteresis is a phenomenon that is present in all ferromagnetic materials. We will use the example of a ferromagnetic material being placed inside a current-carrying coil to help you better understand the idea. The substance becomes magnetized as a result of the magnetic field that is present. Hysteresis is the process of demagnetizing a substance when the direction of the current is reversed.
Hysteretic systems are typically nonlinear systems. Therefore, some hysteretic models, like the Preisach model and the Bouc-Wen model, may find this to be mathematically difficult. In addition, there are models for particular phenomena, such as the Jiles-Atherton model for ferromagnetism, that are phenomenological in nature.
Types of Hysteresis
There are two types of hysteresis.
- Rate-dependent hysteresis: In this type of hysteresis, there is a lag between input and output. We can take the example of a sinusoidal input X(t) resulting in a sinusoidal output Y(t), there is a phase lag φ
X(t)= X0Sin (wt)
Y(t)= Y0Sin (wt – φ)
- Rate-independent hysteresis: The hysteresis that is present in systems has a lingering memory of the past that endures even after the transients have vanished.
Hysteresis Loop (BH Curve)
The relationship between the magnetic flux density and the magnetizing field strength can be seen in the hysteresis loop. The loop is created by monitoring the ferromagnetic material’s magnetic flux while adjusting the external magnetizing field.
If B is calculated for different values of H and the results are plotted graphically, the graph will display a hysteresis loop.
- When the magnetic field strength (H) is increased from zero, the magnetic flux density (B) increases.
- The value of magnetism increases with an increase in the magnetic field until it finally reaches point A, also known as the saturation point where B is constant.
- The value of magnetism decreases when the strength of the magnetic field does as well. Retentivity, or residual magnetism, is the term for the amount of magnetism that a substance or material retains when B and H are equal to zero.
- Magnetism also decreases as the magnetic field moves from the positive to the negative. The material is completely demagnetized at point C.
- Coercive force (C) is the amount of force needed to make a material less retentive.
- Where the saturation point is D, the retentivity point is E, and the coercive force is F, the cycle continues in the opposite direction.
- The cycle is finished as a result of the forward and opposite direction processes, and this cycle is known as the hysteresis loop.
Advantages of the Hysteresis Loop
Less hysteresis loss is indicated by a smaller area of the hysteresis loop.
Hysteresis loop provides a substance with the importance of retentivity and coercivity. Therefore, the heart of machines makes it easier to choose the proper material to create a permanent magnet.
The BH Curve makes it easy to calculate residual magnetism, making material selection for electromagnets straightforward.
Retentivity and Coercivity
When a ferromagnetic material is magnetized by the application of an external magnetizing field, the material does not relax back to its zero magnetization position when the external magnetizing field is removed after magnetization.
Retentivity is the amount of magnetization that remains after the removal of the external magnetizing field.
- It refers to a material’s capacity to hold onto some magnetic properties even in the absence of an external magnetizing field.
- the value of B at the hysteresis loop’s point b.
The coercivity of a substance is the amount of reverse (-ve H) external magnetizing field necessary to completely demagnetize it.
The most common fields where hysteresis occurs are chemistry, physics, engineering, economics, and biology. Others include mechanical hysteresis, optical hysteresis, electron beam hysteresis, adsorption hysteresis, economic hysteresis, ferroelectric hysteresis, superconducting hysteresis, and so on. In any case, we’ll examine a few of the crucial applications of hysteresis.
- In ferromagnets, hysteresis is used in a variety of ways. Hard disks, magnetic tape, and credit cards are a few examples of how it is primarily used to store memory.
- In many artificial systems, including thermostats and Schmitt triggers, hysteresis is used to prevent unintentional frequent or unintentional rapid switching.
- Computer algorithms occasionally include a hysteresis on purpose.
- When a wing’s angle of attack is lowered after stalling, hysteresis can be seen in both the lift and drag coefficients.
- In interfacial rheology experiments involving bubbles, the presence of the bubble shape hysteresis has significant ramifications.
- Cell biology and genetics, immunology, neuroscience, respiratory physiology, voice and speech physiology, ecology, and epidemiology are all areas of biology where it can be found.
In essence, hysteresis occurs frequently and has a wide range of applications in science.
Energy Loss Due to Hysteresis
- Since energy is needed for both magnetization and demagnetization, a transformer is the best object to study energy loss due to hysteresis.
- Energy is expended during the cycle of magnetization and demagnetization of magnetic materials, and this expended energy manifests as heat. Hysteresis loss is the term for this heat loss.
- The area of the hysteresis curve equals the amount of energy lost by the substance per unit volume.
- Energy is continuously lost as heat in transformers as a result of the magnetization and demagnetization process, which reduces the efficiency of the transformer’s energy loss.
- A soft iron core is used in transformers to prevent this energy loss because soft iron has a much lower energy loss or hysteresis loss than other materials.