Contents
Relation between frequency dependence of eddy current loss and switching characteristics of square-loop core. Abstract: It is shown that the reversal time versus excess applied field curve of a square-loop core is equivalent to the relationship between eddy current loss per cycle and frequency at B m = B s .
How do you induce eddy current?
Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor.
How high frequency is heat eddy current?
Therefore eddy current heating can be restricted to any desired depth of the material to be heated by judicious selection of frequency of the heating current. The supply frequency is usually employed between 10 to 400 kHz.
What is difference between induced and eddy current?
The main difference between eddy current and induced current is that induced current refers to currents flowing in coils of wire in a closed circuit whereas eddy current refers to loops of currents flowing within pieces of larger conductors due to electromagnetic induction.
Why do eddy currents create heat?
An alternating current flowing through a coil (A) generates a magnetic field (B). Placing a workpiece (C) within the field induces eddy currents which will create heat, due to the resistance of the material. Heat is produced where—and only where—these eddy currents flow.
Why eddy current is called Eddy?
Eddy currents are named so because the current looks like eddies or whirlpools. When a conductor is placed in the changing magnetic field, the induced current in the conductor is termed as Eddy currents.
How are eddy currents induced by a magnetic field?
Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor.
Why do eddy current losses increase with increasing frequency?
The energy input is the same at both frequencies. But the eddy current losses actualy increase with a square of frequency. That means that at some point you could excede the 100 % efficiency. Why this doesn’t happen?
What are the undesirable effects of eddy currents?
Eddy currents can also have undesirable effects, for instance power loss in transformers. In this application, they are minimized with thin plates, by lamination of conductors or other details of conductor shape. Self-induced eddy currents are responsible for the skin effect in conductors.
Why are eddy currents bad for diffusion weighted imaging?
Eddy currents are particularly problematic in localized spectroscopy, where they cause broadened resonances and distorted line shapes, especially in short TE experiments. At times they may completely prevent the acquisition of localized MRS measurements. In diffusion-weighted imaging, eddy currents can result in spuriously high ADC values.