Handbook for Sound Engineers

264 Chapter 10

Ceramic has a low thermal coefficient of expansion
allowing high inductance stability over a high operating
temperature range.

10.3.1.5 Epoxy-Coated Inductor

Epoxy-coated inductors usually have a smooth surface
and edges. The coating provides insulation.

10.3.1.6 Ferrite Core

Ferrite cores can be easily magnetized. The core
consists of a mixture of oxide of iron and other elements

such as manganese and zinc (MnZn) or nickel and zinc

(NiZn). The general composition is xxFe 2 O 4 where xx

is one of the other elements.

10.3.1.7 Laminated Cores

Laminated cores are made by stacking insulated lamina-

tions on top of each other. Some laminations have the

grains oriented to minimize core losses, giving higher

permeability. Laminated cores are more common in

transformers.

10.3.1.8 Molded Inductor

A molded inductor has its case formed via a molding

process, creating a smooth, well-defined body with

sharp edges.

10.3.1.9 MPP Core

MPP, or moly perm alloy powder, is a magnetic material

with a inherent distributed air gap, allowing it to store

higher levels of magnetic flux compared to other mate-

rials. This allows more dc to flow through the inductor

before the core saturates.

The core consists of 80% nickel, 2–3% molyb-

denum, and the remaining percentage iron.

10.3.1.10 Multilayer Inductor

A multilayer inductor consists of layers of coil between

layers of core material. The coil is usually bare metal

and is sometimes referred to as nonwirewound.

10.3.1.11 Phenolic Core

Phenolic cores are often called air cores and are often

used in high frequency applications where low induc-

tance values, low core losses, and high Q values are

required.

Phenolic has no magnetic properties so there is no

increase in permeability due to the core material.

Phenolic cores provide high strength, high flamma-

bility ratings, and high temperature characteristics.

10.3.1.12 Powdered Iron Core

Powdered iron is a magnetic material with an inherent

distributed air gap that allows the core to have high

Figure 10-24. Various inductor core types.

A. Axial leaded inductor.

Axial leaded

Radial leaded Leadless

B. Bobbins.

C. Radial inductors.

Non-leaded

Leaded

D. Slug cores.

E. Toroidal core.