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In the past, slightly mechanical stress will make the NbCuFeSiB nanocrystalline cores
break, which will lead to the significant enhancement of coercivity Hc and the reduction of
permeability of the cores, thus show the bad mechanical stress magnetic stability……
But nowadays, with advanced surface coating technique made of epoxy resin, we
can produce nanocrystalline cores with excellent mechanical stress magnetic stability.
The nanocrystalline cores weighed 50g are dropped down the ground from1 meter
high level the cores will not break, and also the coercivity and permeability of the
cores remain unchanged.
Because of the excellent comprehensive soft magnetic properties,
it is absolutely possible for NbCuFeSiB nanocrystalline cores to find wide use
in the fields of current(voltage)transformers, voltage independent RCCBs, switched
mode power supplies, common mode chokes, IGBT inverter electric welder to substitute for
cores made from permalloy alloy、silicon steel、ferrite……
*Higher initial permeability(μi=150-260k) and high permeabilits(μm =450-800k): For 30-100mA type AC voltage independent RCCBs.
*High initial permeability and low remerance Br (μi=110-150k,Br=200-400mT):
For 100mA type AC voltage independent RCCBs.
*High initial permeability μi and lower remerance Br(μi=60-130k. Br≤150mT):
For type A 10-100mA,300mA,500mA , type AC 300-500mA voltage independent RCCBs I
and IGBT inverter electric welding mechine.
*High initial permeability μi and high μi/μm (μi=85k-130k, μi/μm≥0.7).
For common mode chokes
*High initial permeability μi and low remerance Br(μi=130-170k. Br≤300mT)
For current transformers and electronic watt-hour meters.
*Temperature magnetic stability:After aging at -25℃ for 100 hours and 120℃ for 100 hours,the
irreversible loss for permeability is less than 2% and less than 3%.
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| Nanocrystalline
soft magnetic cores |
NbCuFeSiB nanocrystalline soft magnetic material is produced by the process of
producing amorphous ribbon(Rapid solidification of molten metal at cooling rate of about
a million degrees per second).During the step, the metal is rapidly quenched as amorphous
ribbon whose thickness is about 30 μm, forming a microstructure of 20
nanometers a –Fe(si) microcrystalline phase, after heat treatment, this kind of material exhibits
excellent soft magnetic properties and is named nanocrystalline alloy.
Before the nanocrystalline soft magnetic material is developed, the widely used soft magnetic
materials were silicon steel、permalloy、ferrite and amorphous, which play a important
role in switched mode power supplies, electric power system equipment, electric meter
and electric apparatus. But soft magnetic properties for the mentioned material are
not perfect, the magnetic properties of all these soft magnetic materials have
disadvantages. The silicon steel has high saturation flux density, but the permeability is very
low particularly in high operating frequency; the ferrite exhibits good high frequency
properties, but the saturation flux density and permeability is low; permalloy shows high
permeability and low coercivity(Hc), but the Bs is low and can not be used in high
operating frequency; the Co-based amorphous presents high permeability and low loss
in wide operating frequency, but the Bs is low and the raw material is expensive;the
Fe-based amorphous has a advantage of high Bs and low price raw material, but the
permeability is relatively low. With high permeability(μi>100000),high saturation flux
density(Bs>1.0T) and low loss(P0.2/50kHz=15w/kg),the nanocrystalline alloy exhibits
excellent soft magnetic properties. The nanocrystalline cores have bright future in the
fields of switched mode power supplies、common mode chokes、current transformers、
voltage independent RCCBs、IGBT inverter electric welder.
Another factor effecting the mechanical stress magnetic stability of nanocrystalline alloy is that
this kind of alloy is very fragile, slightly mechanical stress will make the material break,
which leads to the significant enhancement of coercivity and the reduction of permeability.
This is a magnificent difficult to hinder nanocrystalline alloy to find wide application in industry.
By means of special heat treatment process, we can produce nanocrystalline cores with
low coercivity of 0.2-0.6A/m,high initial permeability of μi equaling to 160-260k.All cores are
surface treated and aged at 120℃ for 3 hour to eliminate the irreversible loss, consequently the
cores show special properties as following:
①.With advanced surface coating technique made of epoxy resin, we can produce
nanocrystalline cores with excellent mechanical stress magnetic stability. Cores
weighed 50g are dropped down the ground from 1 meter high level, the cores will not
break and the permeability and coercivity remain unchanged.
②.Impulse current withstand: when the cores are tested in voltage independent RCCBs with
3000A impulse current, their irreversible loss for permeability is less than 3%.
③.Because of the excellent mechanical stress magnetic stability for the cores, the
use of cores in transformers for IGBT inverter electric welder will greatly reduce the
operating noise and can serve more than 20 years.
④Temperature magnetic stability: after aging at -25℃ for 100 hours and 120℃ for 100 hours,
the irreversible loss for permeability is less than 2% and less than 3%.
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