ASTM A340-03a(2011)
(Terminology)Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
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Designation:A340 −03a(Reapproved 2011)
Standard Terminology of
Symbols and Definitions Relating to Magnetic Testing
This standard is issued under the fixed designation A340; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
In preparing this glossary of terms, an attempt has been made to avoid, where possible, vector
analysisanddifferentialequationssoastomakethedefinitionsmoreintelligibletotheaverageworker
in the field of magnetic testing. In some cases, rigorous treatment has been sacrificed to secure
simplicity, but it is believed that none of the definitions will prove to be misleading.
It is the intent of this glossary to be consistent in the use of symbols and units with those found in
ANSI/IEEE 260-1978 and USA Standard Y10.5-1968.
This terminology is under the jurisdiction of ASTM Committee A06 on
Magnetic Properties and is the direct responsibility of Subcommittee A06.92 on
Terminology and Definitions.
Current edition approved May 1, 2011. Published August 2011. Originally
approved in 1949. Last previous edition approved in 2003 as A340–03a. DOI:
10.1520/A0340-03AR11.
Part 1—Symbols Used in Magnetic Testing
Symbol Term ^ magnetomotive force
ff form factor
α cross-sectional area of B coil H magnetic field strength
A cross-sectional area of specimen ∆H excursion range of magnetic field strength
A' solid area H biasing magnetic field strength
b
B H coercive field strength
c
magnetic induction
H intrinsic coercive field strength
ci
H
magnetic flux density
H coercivity
cs
H demagnetizing field strength
d
∆B excursion range of induction H incremental magnetic field strength
∆
H air gap magnetic field strength
B · biased induction
b g
B remanent induction H ac magnetic field strength (from an assumed
d L
peak value of magnetizing current
B remanence
dm
H maximum magnetic field strength in a hyster-
B H energy product
d d m
(B H ) maximum energy product esis loop
d d m
H maximum magnetic field strength in a flux-
B incremental induction
∆ max
B intrinsic induction current loop
i
H ac magnetic field strength (from a measured
B maximum induction in a hysteresis loop
m p
B maximum induction in a flux current loop peak value of exciting current)
max
H instantaneous magnetic field strength (coinci-
B residual induction
r t
B retentivity dent with B )
max
rs
H ac magnetic field strength force (from an as-
B saturation induction
z
s
sumed peak value of exciting current)
cf crest factor
I ac exciting current (rms value)
CM cyclically magnetized condition
I ac core loss current (rms value)
d lamination thickness c
I constant current
D demagnetizing coefficient
dc
B
I ac magnetizing current (rms value)
df distortion factor m
D magnetic dissipation factor J magnetic polarization
m
k' coupling coefficient
E exciting voltage
E induced primary voltage ! flux path length
! effective flux path length
E induced secondary voltage
! gap length
E flux volts g
f
+ (also φ N ) flux linkage
f cyclic frequency in hertz
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A340−03a (2011)
+ mutual flux linkage ∆χ incremental tolerance
m
L self inductance β hysteretic angle
L core inductance γ loss angle
L incremental inductance cos γ magnetic power factor
∆
L intrinsic inductance γ proton gyromagnetic ratio
i p
L mutual inductance Γ magnetic constant
m m
L initial inductance δ density
L series inductance κ susceptibility
s
L winding inductance ac Permeabilities:
w
m magnetic moment µ ideal permeability
a
M magnetization µ inductance permeability
L
m total mass of a specimen µ L incremental inductance permeability
∆
m active mass of a specimen µ initial dynamic permeability
1 0d
N demagnetizing factor µ peak permeability
D p
N turns in a primary winding µ incremental peak permeability
1 ∆p
N turns in a secondary winding µ instantaneous permeability
2 i
N I/! ac excitation µ impedance permeability
1 1 z
p magnetic pole strength µ incremental impedance permeability
∆z
3 permeance dc Permeabilities:
P active (real) power µ normal permeability
P apparent power µ absolute permeability
a abs
P specific apparent power µ differential permeability
a (B;f) d
P total core loss µ incremental permeability
c ∆
P specific core loss µ effective circuit permeability
c (B;f) eff
P incremental core loss µ intrinsic permeability
c∆ i
P normal eddy current core loss µ incremental intrinsic permeability
e ∆i
P incremental eddy current core loss µ maximum permeability
∆e m
P normal hysteresis core loss µ initial permeability
h 0
P incremental hysteresis core loss µ relative permeability
∆h r
P reactive (quadrature) power µ (also Γ ) space permeability
q v m
P residual core loss µ reversible permeability
r rev
P winding loss (copper loss) µ'/cot γ figure of merit
w
P exciting power ν reluctivity
z
P specific exciting power π the numeric 3.1416
z (B;f)
Q magnetic storage factor ρ resistivity
m
5 reluctance φ magnetic flux
R core resistance φN flux linkage (see +)
R winding resistance χ mass susceptibility
w
S lamination factor (stacking factor) χ initial susceptibility
SCM symmetrically cyclically magnetized condition ω angular frequency in radians per second
T Curie temperature
c
w lamination width
W hysteresis loop loss
h
linear expansion, coefficient (average)
α
Part 2—Definition of Terms Used in Magnetic Testing
ac excitation, N I/ℓ —the ratio of the rms ampere-turns of air-gap magnetic field strength, H —the magnetic field
1 1 g
exciting current in the primary winding of an inductor to the strength required to produce the induction existing at some
effective flux path length of the inductor. point in a nonmagnetic gap in a magnetic circuit.
DISCUSSION—Inthecgs-emusystemofunits, H isnumericallyequal
g
active (real) power, P—theproductofthermscurrent, I,inan
to the induction existing at such a point and exceeds the magnetic field
electrical circuit, the rms voltage, E, across the circuit, and
strength in the magnetic material.
the cosine of the angular phase difference, θ between the
amorphous alloy—a semiprocessed alloy produced by a rapid
current and the voltage.
quenching, direct casting process resulting in metals with
P 5 EIcosθ
noncrystalline structure.
DISCUSSION—The portion of the active power that is expended in a
magnetic core is the total core loss, P .
c
ampere (turn), A—the unit of magnetomotive force in the SI
system of units. The symbolArepresents the unit of electric
aging coefficient—the percentage change in a specific mag-
current, ampere, in the SI system of units.
netic property resulting from a specific aging treatment.
DISCUSSION—The aging treatments usually specified are:
ampere per metre, A/m—theunitofmagneticfieldstrengthin
(a) 100 h at 150°C or
the SI system of units.
(b) 600 h at 100°C.
aging, magnetic—the change in the magnetic properties of a
anisotropic material—a material in which the magnetic prop-
material resulting from metallurgic change due to a normal erties differ in various directions.
or specified aging condition.
anisotropy of loss—theratioofthespecificcorelossmeasured
DISCUSSION—This term implies a deterioration of the magnetic
with flux parallel to the rolling direction to the specific core
properties of magnetic materials for electronic and electrical
applications, unless otherwise specified. loss with flux perpendicular to the rolling direction.
A340−03a (2011)
P cgs-emu system of units—the system for measuring physical
c B;f l
~ !
anisotropy of loss 5
quantities in which the base units are the centimetre, gram,
P
c ~B;f! t
and second, and the numerical value of the magnetic
where:
constant, Γ , is unity.
m
P = specific core loss value with flux parallel to the
c (B;f) l
coercive field strength, H —the (dc) magnetic field strength
c
rolling direction, W/lb [W/kg], and
required to restore the magnetic induction to zero after the
P = specific core loss value with flux perpendicular to
c (B;f) t
material has been symmetrically cyclically magnetized.
the rolling direction, W/lb [W/kg].
coercive field strength, intrinsic, H —the (dc) magnetic field
DISCUSSION—This definition of anisotropy normally applies to elec- ci
trical steels with measurements made in an Epstein frame at a flux strength required to restore the instrinsic magnetic induction
density of 15 kG [1.5 T] and a frequency of 60 Hz (see Test Method
to zero after the material has been symmetrically cyclically
A343).
magnetized.
anisotropy of permeability—the ratio of relative peak perme-
coercivity, H —the maximum value of coercive field strength
cs
ability measured with flux parallel to the rolling direction to
thatcanbeattainedwhenthemagneticmaterialissymmetri-
the relative peak permeability measured with flux perpen-
cally cyclically magnetized to saturation induction, B .
S
dicular to the rolling direction.
core, laminated—a magnetic component constructed by
µ
prl
stacking suitably thin pieces of magnetic material which are
anisotropy of permeability 5
µ
prt
stamped, sheared, or milled from sheet or strip material.
Individual pieces usually have an insulating surface coating
where:
to minimize eddy current losses in the assembled core.
µ = relative peak permeability value with flux parallel to
prl
the rolling direction, and
core, mated—two or more magnetic core segments assembled
µ = relative peak permeability value with flux perpendicu-
prt
with the magnetic flux path perpendicular to the mating
lar to the rolling direction.
surface.
DISCUSSION—This definition of anisotropy normally applies to elec-
core, powder (dust)—a magnetic core comprised of small
trical steels with measurements made in an Epstein frame at a flux
particles of electrically insulated metallic ferromagnetic
density of 15 kG [1.5 T] and a frequency of 60 Hz (see Test Method
material.Thesecoresarecharacterizedbylowhysteresisand
A343).
eddy current losses.
antiferromagnetic material—a feebly magnetic material in
core, tape-wound—a magnetic component constructed by the
which almost equal magnetic moments are lined up antipar-
spiral winding of strip material onto a suitable mandrel. The
allel to each other. Its susceptibility increases as the tem-
stripmaterialusuallyhasaninsulatingsurfacecoatingwhich
perature is raised until a critical (Neél) temperature is
reduces interlaminar eddy current losses in the finished core.
reached; above this temperature the material becomes para-
magnetic.
core loss, ac eddy current, incremental, P —the power loss
∆e
caused by eddy currents in a magnetic material that is
apparent power, P —the product (volt-amperes) of the rms
a
cyclically magnetized.
exciting current and the applied rms terminal voltage in an
electric circuit containing inductive impedance.The compo-
core loss, ac eddy current, normal, P —the power losses as
e
nents of this impedance as a result of the winding will be
a result of eddy currents in a magnetic material that is
linear, while the components as a result of the magnetic core
symetrically cyclically magnetized.
will be nonlinear. The unit of apparent power is the volt-
DISCUSSION—The voltage is generally assumed to be across the
ampere, VA.
parallel combination of core inductance, L , and core resistance, R .
1 1
apparent power, specific, P —the value of the apparent
core loss, ac, incremental, P —the core loss in a magnetic
a(B;f)
c∆
power divided by the active mass of the specimen, that is,
material when the material is subjected simultaneously to a
volt-amperes per unit mass. The values of voltage and
dc biasing magnetizing force and an alternating magnetizing
current are those developed at a maximum value of cycli- force.
cally varying induction B and specified frequency f.
core loss, residual, P —the portion of the core loss power, P ,
r c
area, A—thegeometriccross-sectionalareaofamagneticpath
which is not attributed to hysteresis or eddy current losses
which is perpendicular to the direction of the induction. from classical assumptions.
Bloch wall—a domain wall in which the magnetic moment at core loss, ac, specific, P —the active power (watts) ex-
c(B;f)
any point is substantially parallel to the wall surface. See pended per unit mass of magnetic material in which there is
also domain wall. acyclicallyvaryinginductionofaspecifiedmaximumvalue,
B, at a specified frequency, f.
Bohr magneton—a constant that is equal to the magnetic
moment of an electron because of its spin. The value of the core loss, ac, (total),P —theactivepower(watts)expendedin
c
−21
constant is (9 274 078 × 10 erg/gauss or a magnetic circuit in which there is a cyclically alternating
−24
9 274 078×10 J/T). induction.
A340−03a (2011)
DISCUSSION—Measurements of core loss are normally made with
demagnetization curve—the portion of a flux versus dc
sinusoidally alternating induction, or the results are corrected for
current plot (dc hysteresis loop) that lies in the second or
deviations from the sinusoidal condition.
fourthquadrant,thatis,betweentheresidualinductionpoint,
B , and the coercive force point, H . Points on this curve are
r c
core loss density—the active power (watts) expended in a
designated by the coordinates, B and H .
d d
magnetic core in which there is a cyclically varying induc-
tion of a specified maximum value, B, at a specified
demagnetizing coefficient, D —is defined by the equation:
B
frequency, f, divided by the effective volume of the core.
D 5 Γ H 2 H /B
@ ~ !#
B m a i
DISCUSSION—Thisparameterisnormallyusedonlyfornon-laminated
cores such as ferrite and powdered cores.
where:
H = applied magnetic field strength,
core plate—a generic term for any insulating material, formed
a
H = magnetic field strength actually existing in the mag-
metallurigically or applied externally as a thin surface
netic material,
coating, on sheet or strip stock used in the construction of
B = intrinsic induction, and
i
laminated and tape wound cores.
−7
Γ = 1 in the cgs system and 4π×10 , henry/metre in the
m
coupling coefficient, k'—the ratio of the mutual inductance SI system.
between two windings and the geometric mean of the
DISCUSSION—For a closed, uniform magnetic circuit, the demagne-
individual self-inductances of the windings.
tizing coefficient is zero.
crest factor, cf—the ratio of the maximum value of a periodi-
demagnetizing factor, N —defined as 4π times the demagne-
D
cally alternating quantity to its rms value.
tizing coefficient, D .
B
DISCUSSION—For a sinusoidal variation the crest factor is =2.
demagnetizing field strength, H —a magnetic field str
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