Arnold - Glossary of Terms

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Glossary

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Impedance
The effective electrical "resistance" (ratio of voltage to current) that inductors, capacitors, and resistors present to current flow in a circuit.

Impedance Matching Transformers
Transformers that electrically isolate two circuits but are designed so energy transfer is optimized.

Induced Flux Density
The flux density generated in a core (or soft magnetic material) by the applied MMF.

Inductance
Inductance is the ratio of voltage to time rate of change of current. By definition, it has dimensions of volt-seconds per ampere. A volt-second per ampere is called a "Henry."

Inductance Bridge
An instrument used to measure the inductance of a device directly.

Inductance Factor (A_L)
Core constant used to calculate inductance based on the number of winding turns squared. Value is given in millihenries per 1000 turns squared, which is the same as nanohenries per turn squared.

Induction (B)
Magnetic induction, B, is the magnetic field induced by an applied field, H. It is measured as the flux per unit area normal to the direction of the magnetic path.

Induction Curve, Normal
A graph depicting the relation between normal induction and magnetizing force.

Inductor
A coil that has significant self inductance, typically many turns of wire and with a permeable core. It is a device that stores and releases electromagnetic energy. See Inductance.

Initial Permeability
The relative permeability of a magnetic material at a very low flux level.

Insulator, Insulation
Opposite of conductor, that is, does not conduct an electrical current. In soft magnetic cores, refers to electrical insulation between adjacent laminations, layers of thin gauge tape, or powder particles. Also associated with some of the finishes, which have dielectric capacity, applied to cores.

Intrinsic Coercivity
Same as Hci. Indicates a material's resistance to demagnetization. It is equal to the demagnetizing force which reduces the intrinsic induction, Bi, in the material to zero; measured in oersteds (or kA/m). As for coercivity, the maximum value of intrinsic coercivity is obtained after the material has been saturated (fully magnetized).

Intrinsic Demagnetization Curve
The hysteresis loop corresponding to B versus H where B is the magnetization resulting from only the magnetic material. For the Normal Curve, B corresponds to the sum of the externally applied field and the field of the magnetic material.

Inverter Transformer
A transformer driven in such a manner that an applied DC power is converted to AC power (approximately square wave). Quite often the core is driven into saturation to accomplish this function better.

Irreversible Losses
Defined as partial demagnetization of the magnet, caused by exposure to high or low temperatures, external demagnetizing fields or other factors. These losses can be recovered by re-magnetization. Magnets can be stabilized against irreversible losses by partial demagnetization induced by temperature cycles or by external magnetic fields. Stabilization results in the "loss" prior to placing the magnet in the application and the application is designed around the output of the stabilized magnet.

Isotropic
Having magnetic properties which are independent of the magnet orientation. Most magnetic materials are anisotropic as cast or powdered: each crystallite has a preferred direction of magnetic orientation. If the particles are not physically oriented during manufacture of the magnet, this results in a random arrangement of the particles and magnetic domains and produces isotropic magnet properties. Conversely, orienting the material during processing results in an anisotropic magnet.