The key difference between Hysteresis and Eddy current loss is that hysteresis current loss occurs due to the reversal of magnetism, whereas eddy current loss occurs due to relative motion between a conductor and the magnetic field.
In a transformer, there can be four types of current losses known as resistive loss, eddy current loss, flux loss, and hysteresis current loss. These power losses can eventually end up as heat that needs to be removed from the transformer.
CONTENTS
1. Overview and Key Difference
2. What is Hysteresis Current Loss
3. What is Eddy Current Loss
4. Hysteresis vs Eddy Current Loss in Tabular Form
5. Summary – Hysteresis vs Eddy Current Loss
What is Hysteresis Current Loss?
Hysteresis current loss occurs in transformers due to the magnetization saturation in their core. In this process, magnetic materials in the core eventually become magnetically saturated when the materials are placed in a strong magnetic field, such as a magnetic field that is generated by an AC current.
We can describe hysteresis current loss as a type of energy in electrical machines that occurs due to the repeated magnetization and demagnetization of the iron core. The flow of the alternating current causes the iron core to get magnetized and demagnetized in each cycle. During each of these cycles of magnetization, some of the energy is lost.
To reduce this type of power loss, we can use materials that have less area for the hysteresis loop. Therefore, silica steel or CRGO steel is useful in designing the core within a transformer since it has an extremely small area of the hysteresis loop.
What is Eddy Current Loss?
Eddy current loss can be described as current loops formed over conductor surfaces due to the changing magnetic flux. This type of current loss is important in induction heating, levitating, electromagnetic damping, and electromagnetic braking. We can minimize this type of current loss by adding slots to the conductor surface and laminating.
Figure 01: Laminated Core Eddy Current
An eddy current loss takes place when the changing flux links with the core itself. This induced emf is the core that can set up the circulating current known as the Eddy current. This current can produce a loss known as eddy current loss or I2R loss. Here, it is the value of the current and the R (resistance) of the current path.
Moreover, the magnitude of eddy current can be given when an eddy current “I” is flowing through a core path of resistance “r,” where it can dissipate energy in the form of heat, which can be given in the power equation, power = I2R. This represents the energy that is being expended for no useful purpose, where it is considered as an eddy current loss or iron loss.
What is the Difference Between Hysteresis and Eddy Current Loss?
The key difference between Hysteresis and Eddy current loss is that hysteresis current loss occurs due to the reversal of magnetism, whereas eddy current loss occurs due to the relative motion between the conductor and the magnetic field. Moreover, Hysteresis current loss occurs due to molecular friction in a ferromagnetic material under an alternating magnetic field while eddy current loss occurs due to the induction of eddy current in the core and conductors held in the magnetic field.
The below infographic presents the differences between Hysteresis and Eddy current loss in tabular form for side-by-side comparison.
Summary – Hysteresis vs Eddy Current Loss
Hysteresis current loss is the energy loss that occurs in a transformer due to the magnetization saturation in the core of the transformer, while eddy current loss is current loops formed over conductor surfaces because of the changing magnetic flux. The key difference between Hysteresis and Eddy current loss is that hysteresis current loss occurs due to the reversal of magnetism, whereas eddy current loss occurs due to the relative motion between the conductor and the magnetic field.
Reference:
1. “Hysteresis Loss in a Transformer and How It Affects AC Circuits.” Cadence Design Systems, Inc., 17 Mar. 2022.
Image Courtesy:
1. “Laminated core eddy currents” By Chetvorno – Own work (CC0) via Commons Wikimedia