How eddy current is used as damping?
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. If the bob is metal, there is significant drag on the bob as it enters and leaves the field, quickly damping the motion.
How do we reduce the eddy currents?
Eddy current magnitude can be reduced by designing the core as a set of thin sheets or laminations, in parallel to the magnetic field. Each sheet must be insulated from its neighbours with a thin coating of varnish or oxide film. By laminating the core, the area of each section and hence the induced EMF is reduced.
In which instrument eddy current damping is used?
Points to remember:
| Type of damping | Instruments used |
|---|---|
| Air friction damping | Moving iron (MI) and EDM (Electro dynamometer) instruments |
| Fluid friction damping | Electro-static voltmeter (ESV) and Induction type instruments |
| Eddy current damping | PMMC and induction type (which are used permanent magnet) |
| Electromagnet damping | Flux meter |
What affects magnetic damping?
The amount of energy transferred to the conductor in the form of heat is equal to the change in kinetic energy lost by the magnet – the greater the loss of kinetic energy of a magnet (a product of its mass and speed), the greater the heat buildup in the conductor and the more forceful the damping effect.
How many ways can the damping be provided in an indicating instrument?
There are four different ways of producing damping torque, these include air friction damping, fluid friction damping, eddy current damping, and electromagnetic damping.
How do eddy currents produce heat?
(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.) In the area where the eddy currents are flowing, the phenomenon of resistance then generates heat.
Why eddy current damping is not used in MI instruments?
Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument.
Why is eddy current damping in Pmmc?
When a current flow through the coil, it generates a magnetic field proportional to the current in an ammeter. Damping is caused by the eddy current set up in the aluminium coil, which prevents the oscillation of the coil.
What are eddy current and electromagnetic damping?
Electromagnetic damping is one of the most interesting damping techniques, which uses electromagnetically induced currents to slow down the motion of a moving object without any physical contact with the moving object. Thus the eddy currents swirl in a plane perpendicular to the magnetic field.
How do you determine eddy current?
The direction of eddy current flow can be deduced by the “ right hand rule” and by the requirement that the reaction magnetic flux produced by the eddy currents must flow in the opposite direction to the flow of excitation flux.
What are different methods of damping?
There are four different ways of producing damping torque, these include air friction damping, fluid friction damping, eddy current damping, and electromagnetic damping. Air friction damping is created by a piston oscillating in and out of an air chamber.
How is eddy current produced?
Eddy currents are produced in metals when the metal is subjected to a magnetic field. Note that there is no electric source in this case and the currents are formed because of the magnetic field itself.
What is an eddy current drive?
An eddy current drive (sometimes called a Dynamatic drive, after one of the most common brand names) consists of a fixed speed motor (generally an induction motor) and an eddy current clutch.
What is electromagnetic damping?
Definition of electromagnetic damping. Commonly found in seismometers of the induction type. It may be used in mechanical seismographs by employing a copper plate moving between two permanent magnets. Induction seismometers depend upon voltage generated by motion of coil in the magnetic field. Ref: AGI.