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Eddy Current

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Last updated date: 19th Jul 2024
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An Introduction to Eddy Current

Prior to obtaining a clear scenario on Eddy now, let us begin to know its set of experiences, how it was created, and what are its improvements. 

The initial researcher to investigate the idea of Eddy Current was Arago in the year 1786 - 1853. Though in the time frame between 1819 – 1868, Foucault acquired credits in the disclosure of Eddy Current. 

Furthermore, the principal use of Eddy Current happens for a non-damaging investigation that occurred in the year 1879 when Hughes carried out the ideas of leading metallurgical ordering tests. 

Presently, this page gives a reasonable clarification of the eddy current generator, eddy current principle, and the use of eddy current.

Eddy Current Principle 

An eddy current is also called the Foucault current. Eddy currents are swirls of electric currents induced within conductors by a changing magnetic field within the conductor (self-inductance).  Eddy current works on the principle of Faraday’s law of induction. 

The Eddy Current Principle works as the Self-inductance. 

One must note that Eddy currents can be induced within nearby static conductors by a time-varying magnetic field created by an AC electromagnet or transformer. For instance, by relative motion between a magnet and a conductor (Eddy Current Aluminium).

On this page, you will learn about the Eddy current and the use of Eddy current in detail.  

Eddy Current Flow

Eddy current flows in a closed loop within the conductors only and always acts in a plane perpendicular to the magnetic field. 

The magnitude of the current in a given circle is relative to the strength of the magnetic field, the area of the circle, the pace of magnetic flux, and conversely corresponding to the resistivity of the material. 

At the point when charted/graphed, these roundabout flows inside a piece of metal look enigmatically like Eddies or whirlpools in a fluid. 

Eddy Current Magnetic Field 

Eddy currents are likewise called Foucault's currents and flow where these streams around the conductors pivot in whirls in streams. These are simulated by fluctuating the magnetic fields and development in closed rings, which are in a vertical situation to the magnetic field's plane (Eddy Current Magnet). 

Eddy current flow can be created when there is a conductor movement across the magnetic field or when there is variety in the magnetic field that encases the fixed channel.

This implies that anything that results in the conductor faces a changeover either in the direction of the magnetic field or intensity and this conveys these circling current flows. The magnitude of this current has the direct extent to the magnetic field magnitude, circle cross-sectional region, and measure of flux in the transition and has a converse relative rate to the conductor's resistivity. This is the fundamental Eddy Current Principle.

By Lenz's law, a swirling or an Eddy current makes a magnetic field that goes against the change in the magnetic field that made it, and accordingly, Eddy Current (whirlpool flows) reacts back on the source of the magnetic field. 

For instance, a close-by conductive surface will apply a drag power on a moving magnet that goes against its movement, because of eddy current induced in the surface by the moving magnetic field.

Use of Eddy Current

This impact is utilized in Eddy current brakes which are utilized to quit pivoting power apparatuses immediately when they are stopped. The current coursing through the opposition of the conductor additionally scatters energy as warmth in the material.

Eddy Current Generator

A magnet actuates roundabout electric flows in a metal sheet travelling through its attractive field. See the graph at right. It shows a metal sheet (C) moving to one side under a fixed magnet. The attractive field (B, green bolts) of the magnet's north pole N goes down through the sheet. 

Eddy Current Aluminium

Since the metal (aluminum/copper) is moving, the flux through a given territory of the sheet is evolving. In the piece of the sheet moving under the main edge of the magnet (left-side) the magnetic field through a given point on the sheet is expanding as it gets closer to the magnet, {dB/dt > 0}. 

From Faraday's law of enlistment, this makes a looping electric field in the sheet a counterclockwise way around the magnetic field lines. This field initiates a counterclockwise progression of electric flow (I, red), in the sheet. This is the Eddy current.


Use of Eddy Current

Eddy currents are used to heat objects in induction heating furnaces and equipment, and to distinguish breaks and defects in metal parts utilizing Eddy current testing instruments.

Eddy Current Separator

An Eddy current separator utilizes an incredibly magnetic field to isolate non-ferrous metals from wastage after all ferrous metals have been taken out already by some previous arrangement of magnets.           

The device utilizes Eddy’s current flow to impact the separation. The Eddy current separator is not intended to sort ferrous metals which become hot inside the swirl current field, as this can prompt harm to the separator unit belt.

Benefits of Eddy Current

  • This method is particularly effective in the analysis process

  • This is a non-impact analysis process that does not show an impact on the work

  • The analysis is completely fast and gives accurate results

  • The cover is easily analyzed which is used in many products

  • It is even used on a speedometer device and in the process of an indoor furnace.

Disadvantages of Eddy Current

  • As a result of this process, there will be a leak of magnetic flux

  • Severe heat loss occurs due to cyclic currents due to the collision of the magnetic circuit. With this electric current, it wastes as a form of heat

Eddy Current Applications

  • It is done on trains with eddy current brakes

  • It is used to provide decent torque to PMMC devices

  • It is used in electrical devices as an input power meter

  • These are used to determine the damage to the metal sections

Eddy Currents Properties

  • These are made only within the operating equipment.

  • These are distorted by faults such as cracks, rust, edges, etc.

  • Eddy currents diminish in-depth with the larger forces present above.

These structures lead to the widespread use of eddy currents in energy, aerospace, and petrochemical industries to detect cracking and metal damage.

Causes of Eddy Currents

When the conductor moves in a magnetic field or when the magnetic field surrounding a vertical conductor changes, eddy currents are produced. Eddy currents can therefore be made whenever the strength or direction of the magnetic field changes in the conductor.

We know from Lenz Law that the direction of induced current, like eddy current, will be such that the magnetic field created by it opposes the changes in the magnetic field that it caused. The electrons in the conductor rotate in a plane that relies on a magnetic field for this to happen. The size of the eddy current is:

  • Depending on the size of the magnetic field

  • Equivalent to the loop area

  • In proportion to the degree of fluctuations of the magnetic fluctuations in reverse

  • In line with the resistance of the conductor

Eddy currents often fight off changes in the magnetic field they produce, resulting in a loss of power to the conductor. These convert heat into heat, such as kinetic or electrical energy. In order to stabilize rotating power tools and rollercoasters, we use resistance caused by opposing backgrounds to produce eddy currents.

FAQs on Eddy Current

1. What is the Formula For the Eddy Current Loss?

Eddy currents are created when a conductor goes through changing magnetic fields.

Since Eddy currents are ideal and not utilitarian, these force a loss in the magnetic substance and are known as Eddy Current Losses. Similarly, as hysteresis losses, Eddy currents likewise improve the magnetic substance temperature. These losses are aggregately named magnetic/core/iron losses.

Let us suppose that Eddy current flow occurs in the following transformer:

The magnetic flow in the inward segment of the transformer's center animates emf in the center dependent on Lenz and Faraday's laws which permit the progression of current into the center. The Eddy Current Loss formula is given by:

=  kef2Bm2T2


ke = a constant value that depends on the magnitude and has an inverse relationship with the conductor’s resistivity.

f = excitation material’s frequency range

Bm = maximum value of the magnetic field

T = thickness of a material

2. How to Minimize Eddy Current Losses?

Eddy currents are a reason for energy loss in exchanging flow (AC) inductors, transformers, electric engines and generators, and other AC hardware, requiring uncommon construction, for example, laminated magnetic cores or ferrite cores to limit them. To limit these current losses, the center segment in the transformer is created by amassing thin sheets named laminated and each individual plate is protected or cleaned. With this staining, the Eddy current development is confined to an insignificant level of the cross-section area of each individual plate and protected from different plates. Along these lines, the stream direction of the current arrives at a little value.

3. What are the uses of Eddy currents?

Eddy currents are currents that form on the conductor surface due to magnetic fluctuations. They are useful for heat transfer, gravity, magnetic field, and electric braking. It can be reduced by adding spaces in the conductor & laminating area. They flow through closed loops in an airplane that relies on a magnetic field. By Lenz law, current swirls in such a way as to create a magnetic field that resists change; in order for this to happen to the conductor, electrons fly in a plane toward the magnetic field.

4. What are the applications of eddy currents on the rail brakes?

Due to the tendency of the eddy currents, the eddy currents cause energy loss. Eddy currents convert very useful energy sources, such as kinetic energy, into heat, which are not commonly used. During braking, the brakes put metal wheels in place on the magnetic field that produces eddy currents on the wheels. Magnetic interaction between the field used and the eddy currents used to lower the wheels. When the wheels run faster, the effect becomes stronger, which means that as the train decreases the braking force decreases, producing more stable movement.

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