How eddy current is used as damping?

How eddy current is used as damping?

When a conductive material is subjected to a time-varying magnetic flux, eddy currents are generated in the conductor. As the eddy currents are dissipated, energy is removed from the system, thus producing a damp- ing effect.

What is damping eddy current damping?

Definition. When a magnetic field moves through a conductor the movement induces an eddy current in the conductor. Eddy currents induced in conductors are much stronger as temperatures approach cryogenic levels. This allows for critical damping for cryogenic applications and testing in the aerospace industry.

What is eddy current effect?

Eddy currents (also called Foucault’s currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday’s law of induction. This effect is employed in eddy current brakes which are used to stop rotating power tools quickly when they are turned off.

What are the applications of eddy current?

Typical applications for eddy current testing include:

  • Crack detection.
  • Tube and wire testing.
  • Condenser tube inspection.
  • Material sorting.
  • Weld testing.
  • Coating thickness measurement.

What is eddy current formula?

Next, the eddy current flowing in each ring is obtained by solving a complex matrix equation of the form [X] [I] = [V] where X is the impedance matrix, I is the eddy current matrix, and V is the induced voltage matrix.

How eddy current is produced?

They can be created when a conductor is moving through a magnetic field, or when the magnetic field surrounding a stationary conductor is varying i.e. anything which results in the conductor experiencing a change in the intensity or direction of a magnetic field can produce eddy currents.

Which damping is used in Pmmc?

eddy current damping
In PMMC instruments, the damping torque is provided by eddy current damping since the presence of a permanent magnet.

Why is eddy current bad?

Eddy current can result in the loss of electrical energy in the form of heat. There will be a magnetic flux leakage in induction coils due to eddy current.

What is the disadvantage of eddy current?

Disadvantages of Eddy Currents: There is a major heat loss during cycling eddy currents due to friction in the magnetic circuit, especially where the core is saturated. Thus there is the loss of useful electrical energy in the form of heat. There is magnetic flux leakage.

What is the advantage of eddy current?

The advantages of eddy current testing are: Sensitivity to surface defects. Able to detect defects of 0.5mm in length under favourable conditions. Can detect through several layers.

Is eddy current useful?

Eddy currents. An eddy current is a current set up in a conductor in response to a changing magnetic field. Because of the tendency of eddy currents to oppose, eddy currents cause a loss of energy. Eddy currents transform more useful forms of energy, such as kinetic energy, into heat, which isn’t generally useful.

What are the disadvantages of eddy current?


  • Method restricted to conductive materials.
  • Inspection of ferromagnetic materials can be impacted by magnetic permeability.
  • Depth of inspection (penetration) is limited.
  • Skill and training required is more extensive than other techniques.
  • Surface finish and roughness may interfere.

How are eddy currents and magnetic damping related?

Since eddy currents and magnetic damping occur only in conductors, recycling centers can use magnets to separate metals from other materials. Trash is dumped in batches down a ramp, beneath which lies a powerful magnet. Conductors in the trash are slowed by magnetic damping while nonmetals in the trash move on, separating from the metals.

How are eddy currents related to motional EMF?

As discussed in Motional Emf, motional emf is induced when a conductor moves in a magnetic field or when a magnetic field moves relative to a conductor. If motional emf can cause a current loop in the conductor, we refer to that current as an eddy current. Eddy currents can produce significant drag, called magnetic damping, on the motion involved.

How is the eddy current set up in the field?

As it enters from the left, flux increases, and so an eddy current is set up (Faraday’s law) in the counterclockwise direction (Lenz’s law), as shown. Only the right-hand side of the current loop is in the field, so that there is an unopposed force on it to the left (RHR-1).

How does a metal plate affect the eddy current?

When the metal plate is completely inside the field, there is no eddy current if the field is uniform, since the flux remains constant in this region. But when the plate leaves the field on the right, flux decreases, causing an eddy current in the clockwise direction that, again, experiences a force to the left, further slowing the motion.

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