CS1027 datasheet(40/42 Pages) ETC

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Magnetic Powder Cores :::

77 ::: Chang Sung Corporation

AL Value (nH/N2)

The inductance (nanohenries) of a core for 1 turn winding. It is measured

at peak AC flux density of 10 gauss and frequency of 10kHz. 1nH/N2 =

1mH/(1000turns)2

Ambient Temperature

Temperature surrounding the devices or circuits. The ambient temperature

is measured at 0.5inch(1.27cm) away from the devices or circuits.

Attenuation

The ratio of output parameter (voltage, current, power, etc.) to input

parameter. Unit is [dB]. In the case of power, dB is10log (output power /

input power). In the case of current and voltage, dB is 20log (output

current /input current), 20log (output voltage / input voltage)

respectively.

Coercive Force (Hc) Refer to Hysteresis Curve.

Common-Mode Noise

Electrical interference that is common to both lines in relation to the

ground.

Copper Loss [watts]

The power loss (I2R) or heat generated by current (I) flowing in a winding

with resistance (R).

Core loss [watts]

Core loss is composed of eddy current loss, hysteresis loss and residual

loss. Refer to Magnetic Design Formulae.

Cross Sectional Area (A)

The effective cross sectional area of a core available for magnetic flux.

The cross sectional area listed for toroidal cores is based on bare core

dimensions.

Curie Temperature, Tc [ ]

The transition temperature above which a core loses its

ferromagnetic properties. Usually defined as the temperature at which

falls to 10% of its room temperature value.

DC Resistance [ ]

Resistance of winding when AC current is not applied.

Differential Mode Noise

Electrical interference that is not common to both lines but is

present between both lines. This is also known as normal mode noise.

Disaccommodation

The proportional change of permeability after a disturbance of a

magnetic material. It is measured at a constant temperature over a given

time interval.

Distributed Capacitance

In an inductor, each winding behaves as a capacitor having the

distributed capacitance. Distributed capacitance is parallel with

inductance in the circuit and causes self-resonance at a certain

frequency. An inductor which has a smaller distributed capacitance

extends a much higher self resonant freguency. So the inductor should

be wound to have as small a distributed capacitance as possible.

Eddy Current

When a varying electric or magnetic field

passes through the conducting material,

current which opposes the change of field

is induced in it. This current is called eddy

current. Because a conducting material

has electric resistance, the eddy current

results in heat loss. This is referred to as

the eddy current loss.

Effective Permeability (μe) Refer to Permeability.

EMI

The acronym for Electromagnetic Interference is EMI.

Generally, EMI refers to unnecessary electrical energies such as noise.

EMC Electromagnetic Compatibility

Hysteresis Curve (B-H Loop)

When the magnetic material is taken through a complete cycle of

magnetization and demagnetization, the magnetic flux density in that

material behaves irreversibly according to the change of the magnetizing

force.

The results are as shown in Figure 2. As H is increased in the neutral

magnetic material, flux density B increases along the dashed line (initial

magnetization curve) to the saturation point, Bs.

Figure 1. Eddy Current in Powder Cores

Figure 2. B-H Loop

When H is now decreased, the B-H loop transverses a path to Br

(remanent flux density), where H is zero and the core is still magnetized.

The magnetizing force H is now reversed to give a negative value. The

magnetizing force required to reduce the flux Br to zero is called the

coercive force (Hc). Along the initial magnetization curve, B increases

from the origin nonlinearly with H until the material saturates. In

practice, the magnetization of a core in an excited inductor never follows

this curve because the core is never in a totally demagnetized state

when the magnetizing force is first applied.

Flux Density, Magnetic Induction, B [Gauss ; Tesla]

The corresponding parameter for the induced magnetic field in an area

perpendicular to the flux path. Flux density is determined by the field

strength and permeability of the medium in which it is measured.

1T=104 Gauss

Incremental Permeability(

μ)

Refer to Permeability.

nductor

A passive device that prevents a variance of the current. Magnetic flux is

induced in the inductor when current flows through the inductor, and

the voltage induced by magnetic flux prevents the change of current.

Induced voltage

= L di/dt.

Initial Permeability(μi)

Refer to Permeability.

Leakage Flux

Leakage flux is the small fraction of the total magnetic flux in a

transformer or common mode choke that does not contribute to the

magnetic coupling of the windings of the device. The presence of

leakage flux in a transformer or common mode choke is

modeled as a small "leakage" inductance in series with each

winding. In a multi-winding choke or transformer, leakage

inductance is the inductance measured at one winding with all other

windings short circuited.

Litz Wire

A wire made by twisting and bundling some insulated wire.

It can decrease the copper loss at high frequency by reducing

the skin effect.

Magnetic Hysteresis

Refer to Hysteresis Loop.

Magnetizing Force, H [Oe ; A/m]

The magnetic field strength which produces magnetic flux. The mmf per

unit length. H can be considered to be a measure of the strength or

effort that the magnetomotive force applies to magnetic circuit to

establish a magnetic field. H may be expressed as H=NI/ , where

the mean length of the magnetic circuit in meters.

1 oersted=79.58A/m

Mean Magnetic Path Length( )

The effective magnetic path length of a core structure (cm).

Refer to Magnetic Design Formulae.

Normal Mode Noise

Refer to Differential Mode Noise.

Noise

Unnecessary electrical energy that rises in a circuit.

Operating Temperature Range

The temperature at which a device can be operated normally. Above this

temperature, the characteristics of the device can become inferior or the

device may operate abnormally. In the case of the inductor, this

temperature refers to the temperature rise by the copper loss or core

loss. Refer to temperature rise.

Permeability(μ)

In magnetics, permeability is

the ability of a material to

conduct flux. The magnitude

of the permeability at a given

induction is a measure of the

ease with which a core

material can be magnetized to

that induction. It is defined as

the ratio of the flux density B

to the magnetizing force H.

Permeability : μ = B/H [Gauss/Oersted]

The slope of the initial magnetization curve at any given point gives the

permeability at that point. Permeability can be plotted against a typical B-

H curve as shown in Figure 3 Permeability is not constant, therefore its

value can be stated only at a given value of B or H. There are many

different kinds of permeability.

Absolute Permeability(μo)

Permeability in a vacuum

Initial Permeability(μi)

Slope of the initial

magnetization curve at the

origin, that is, the value of

permeability at a peak AC flux

density of 10 gauss

(1 millitesla).

μ= B/H (Figure 4)

Incremental Permeability( μ)

The slope of the magnetization curve for finite values of peak-to-peak

flux density with superimposed DC magnetization (Figure 5). Initial

permeability can be thought of as incremental permeability with 0 DC

magnetization at small inductions. The incremental permeability is

expressed as the slope of the B-H characteristic at around the given

operating point.

Figure 3. Variation of

along

the Magnetization Curve

Figure 4. Initial Permeability

Terminology

Metal Powder

Ceramic Layers

Eddy Current

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