T.O. 33B-1-1
4-1
CHAPTER 4
SECTION I
INTRODUCTION TO EDDY CURRENT INSPECTION
4
EDDY CURRENT INSPECTION.
4.1
INTRODUCTION.
This method is used detect discontinuities in parts that are conductors of electricity. An eddy current is the circulating
electrical current induced in a conductor by an alternating magnetic field. When eddy currents encounter an obstacle,
such as a crack, the surrounding currents become distorted. This change is detected on a meter or other type of display.
4.1.1
Definition of Eddy Currents.
Eddy currents are electrical currents induced in a conductor by a changing magnetic field. The eddy currents are
circular in nature, and their paths are oriented perpendicular to the direction of the magnetic field. Eddy current
nondestructive inspection can determine some properties of materials, locate discontinuities, and measure dimensions.
The eddy currents are usually generated by the flow of alternating or otherwise varying electric currents in coils placed
near an electrically conductive part. Figure 4-1 illustrates eddy currents flowing in various configurations.
Figure 4-1. Generation of Eddy Currents in Various Part Configurations.
