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Amorphous Magnetic Cores For High Frequency Electronics

Amorphous magnetic cores allow smaller, lighter and more energy efficient designs in many high frequency applications for Invertors, UPS, ASD(Adjustable speed drives), and Power supplies (SMPS). Amorphous metals are produced in using a rapid solidification technology where molten metal is cast into thin solid ribbons by cooling at a rate of one million�C/second. Amorphous magnetic metal has high permeability due to no crystalline magnetic anisotropy.

Amorphous magnetic cores have superior magnetic characteristics, such as lower core loss, when compared with conventional crystalline magnetic materials. These cores can offer superior design alternative when uses as the core material in the following components:

AC Reactor | DC Reactor | PFC boost inductor: Under 6kW (Mircolite 100µ)Over 6kW
Common mode chokes | MagAmp | Differential mode chokes / SMPS output inductor
Spike absorbing cores

Technical advantage

Where typical ferrite cores can only operate up to a flux saturation level (Bsat) of 0.49 Tesla, amorphous metal cores can be operated at 1.56 Tesla. Combined with operating at permeability similar to high-end ferrites and the flexibility of manufacturing large cores sizes these cores can be an ideal solution for many of these components.

Nanocrystalline amorphous metal offers size, core and labor savings for various EMC applications.


Microlite 100μ

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These cores are ideal candidates for PFC boost inductor applications in power supply ranges from 300 to 6kW (for higher power design see Powerlite).  Microlite 100 are tape wound amorphous toroidal cores with a small gap, which allows the core to achieve permeabilities less than 245. The material is stable over a wide temperature range and offers a design with fewer and smaller gaps than comparable E-core ferrites. The fewer gaps and smaller gap size greatly reduces EMC concerns from fringing flux and stray field. Most designs can be constructed with few turns and lower losses providing a smaller more cost effective design. In some cases these cores maybe a good alternative for differential input inductors, and SMPS output inductors.

MICROLITE 100 m Cores vs. The Competition  -  Properties



Iron Powder


Kool Mu




1.0 to 1.4









Gap Dependent

Power Loss (W/Kg)






% Permeability at 100 Oe





Gap Dependent

This comparison was done using 2500 perm ferrite and core loss comparison performed at 100 kHz and 1 kG BAC

To choose the best core for your design down load the PFC calculator:

Executable | Zip file

  • Data sheet for ordering: (link: Core Specifications for Ordering)
  • PFC Design benefits: (link: Product Overview (PDF)159k )
  • Technical data sheet: (link: Technical Bulletin (PDF) 104k)

Technical Charts


Temperature Dependence of Inductance


vs DC Bias


Bias Characteristics of Inductance


Core Loss vs. Magnetic Induction and Frequency

Powerlite C-cores
These amorphous cores wound in a C-core configuration, are ideal for AC Reactors and DC inductors from 10 to 1000+ amperes. The C-core also allows for single phase and three phase transformer designs.
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Three phase designs can be done with standard single-phase cores or a custom three-phase core can be constructed in a two-piece set as shown below:

Amorphous metal C-cores allow for operation at higher frequencies at the same flux level. Where traditional steel cores need to operate at increasingly lower flux densities as the frequency increases. In order to compensate for running at lower flux densities significantly more material is needed. Even with additional material higher temperatures still occur. Another contributor to lowering losses is the I2R of the winding. A physically smaller amorphous core reduces your mean length per turn, hence your I2R copper losses are lower and copper costs are lower.


Winding options

For higher current applications these cores open up the new options for the conductor winding process that is not easily achievable for toroidally constructed cores:

  • Copper foil
  • Large gauge square conductors
  • Edge or disc winding.

In each of the above options, the winding can be accomplished on a separate mandrel and assembled onto the C-core after the winding process. Litz is wire commonly used for high current/high frequency designs. However, terminating litz wire for these applications can be expensive. An alternative to consider is disc or edge winding. This involves winding a rectangular wire that has a relatively high aspect ratio on its edge The quasi-planar structure reduces the skin effect, but not as great as using litz wire although greater than can be realized with similar magnet wire or copper foil. Other advantages are: lower copper loss, reduced DCR, smaller size, improved heat dissipation.

Higher wattage switching devices allowing operating frequencies of 10 and 20kHz are now becoming cost effective for the high power designer. In the past traditional EI and UI laminated inductors using 3% Ni, silicon grain oriented steel could be used with little problem. 3 percent nickel, silicon grain oriented steel appears to be dead above 1kHz. Special design considerations that take into account the lower flux densities at these frequencies allow this material to be pushed beyond its normal intended application. This however can result higher temperatures and much larger core sizes than with a comparable amorphous core design. These are summarized in the below chart:


Amorphous cores for high frequency inductors verses competitive materials

Parameters Amorphous
6% Si
3% Si
1.0 to 1.4
2 to 75
Power Loss (W/Kg)

This design assumes 50% permeability with 50 Oe of bias, 2500 perm ferrite was used for comparison and core determined at 20 kHz and 2 kg BAC

When comparing Iron Powder to Amorphous core. The Amorphous core will tend to be less expensive, and have lower losses, smaller physical size, better heat dissipation, and are mechanically rugged



To choose the best core for your design, download following calculators:

DC Reactor Executable Zip file
AC Reactor Executable Zip file
  • Data sheet for ordering: (link: Core Specifications for Ordering)
  • PFC Design with C-cores (link: PFC Application Guide PDF Format 828k )
  • Technical data sheet:   (link: Technical Bulletin PDF Format 305k)

Technical Charts

1 Core Loss vs. Flux Density @ 25�C
2 Saturation Induction vs. Temperature
3 Permeability vs. Temperature
4 C-Cores - Mounting Methods
5 C-Cores - Bobbins



Magnetization curves:

For larger kilowatt power supplies,. High frequency transformers using these C-core offer higher saturation induction of 1.56 Tesla and lower losses allowing for:

  • higher efficiency
  • lower transformer weight
  • reduced transformer volume



Powerlite forms

We produce rectangular shapes of amorphous metal cores by stacking layers of laminations made from amorphous metal ribbon. An adhesive rated for a continuous operating temperature of 155°C holds the laminations together.

These forms offer a unique combination of high saturation induction (1.56 T), high permeability and low core loss and can be configured into various shapes, allowing for one large gap to be distubuted across several smaller gaps, reducing fringing flux, and core loss.

Possible configurations:
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Hybrids and be designed using c-core sections with corresponding bricks for unique shapes

Applications: Medium Frequency and High Power Inverters

  Technical data sheet:   (link: Technical Bulletin PDF Format 305k)

Toroidal Amorphous Cores
These are offered in various amorphous metals depending on your application  



Common mode chokes Nanocrystalline
Spike killers Nanocrystalline
Magnetic Amplifiers Cobalt Alloy
Differential mode chokes Partly crystallized iron alloy
Products Material  
Microlite Partly crystallized iron alloy Sizes to match industry standard 125 permeability material
Microlite XP Partly crystallized iron alloy Sizes to match application requirements.
Magnaperm Cobalt Alloy  
Finemet Nanocrystalline  

MicroLite® Toroidal Choke Cores from Metglas® are manufactured with iron-based Metglas® amorphous Alloy-SA1. They offer a unique combination of high saturation induction, high permabiliity and the lowest core loss available for high frequency choke cores allowing the use of significantly smaller sizes than possible with conventional materials.

dc Output Inductors; Flyback Transformers; Differential Mode in Chokes; PFC Boost Chokes - Continuous Mode.


Links and data sheets for down load

Core Loss vs. Flux Density @ 25�C
Percent Permeability vs. dc Bias
Temperature Dependence of Inductance
Temperature Dependence of Inductance and Permeability vs. Frequency
Core Specifications For Ordering
Technical Bulletin (333k)

MICROLITE XP products are made of amorphous alloys, which are non-crystalline in nature. Metglas� MICROLITE XP cores operate cooler and have lower core losses than cores made of conventional crystalline materials such as powdered iron, ferrite or sendust. MICROLITE XP's energy-efficient properties reduce the size of powder sources for demanding applications in the electronics industry

Differential Input Inductors, PFC Inductors, Flyback transformers, and VRM Inductors.


Links and data sheets for down load

Core Loss vs. Flux Density @ 25�C
Percent Permeability vs. dc Bias
Temperature Dependence of Inductance 
Temperature Dependence of Inductance
and Permeability vs. Frequency
Core Specifications For Ordering
Technical Bulletin (333k) 

MagnaPerm� High Permeability Cores are manufactured with cobalt-based Metglas amorphous alloy 2714AF for high frequency applications. Theses flat loop toroidalcores offer a unique combiation of ultra-high permeability, high saturation flux density and extremely low core loss for electronic component designers.

EMI Common Mode Filtering; Telecommunications and Data Communications Interface Transformers; High Accuracy Current and Pulse Transformer Ground Fault Protection Devices.


Links and data sheets for down load

Complex Parallel Permeability vs. Frequency
Complex Series Permeability vs. Frequency
Tan vs. Frequency 
Tan vs. Temperature
Percent Change of Permeability vs. Temperature
Amplitude Permeability vs. Flux Density
Incremental Permeability vs. dc Bias 
Core Loss vs. Temperature 
Core Loss vs. Flux Density 
Core Specifications For Ordering
Technical Bulletin (PDF)193k 

Metglas® Square Loop Cores manufactured with cobalt-based Metglas® amorphous Alloy 2714A allow the design of mag amps that can operate at higher frequencies than previously possible. Their combination of magnetic properties enable mag amps to provide unparalleled precision and efficiency in output regulation.

Saturable Reactors; Magnetic Amplifiers.



Links and data sheets for down load

Core Loss vs. Flux Density
BSAT, Br/BSAT vs. Temperature
Coercive Field vs. Frequency
Coercive Field vs. Temperature
Core Specifications for Ordering

Nanocrystalline common mode choke coils and cores
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Single-phase cores

These are toroidal shaped tape-wound cores made from nanocrystalline amorphous metal. Our products offer a superior technical solution for many EMC problems when compared to Mn-Zn ferrite choke.

File written by Adobe Photoshop� 4.0

Three-phase cores

These advantages are:

  • High permeability and low Q factor providing higher impedance over a wide frequency range. Hence, offering excellent performance in noise suppression over wide frequencies.
    For example when nanocrystalline chokes and Mn-Zn ferrite chokes have same inductance value at 100kHz, Nanocrystalline chokes show impedance two times higher than that of Mn-Zn ferrite chokes. Another advantage is that Nanocrystalline chokes require fewer windings to obtain the same inductance value as Mn-Zn ferrite chokes, creating lower stray capacitance and maintains high impedance at frequencies greater than 1 MHz
  • Temperature changes do not significantly affect the frequency characteristics of impedance. Resulting in high noise suppression performance over a wide temperature range

Download EMC brochure for information on common mode components:


Sizes offered

Standard wound common mode and choke cores are available as standard products for DC and single-phase AC power lines (rated current from 5A to 40A), and for three-phase AC power line (rated current from 3A to 600A).

Single-phase vertical mount Single-phase horizontal mount

Three-phase wound components

Custom designs are available upon request, for your application your can pick the standard product that most closely meets your needs, or fill out our request form for a recommendation.

Typical applications include various portions of the power supply / inverter such as input single and three phase noise filters, active harmonic filters, output noise filters, DC Power Lines or Signal Lines. 

Download EMC brochure for information on common mode components:  

Nanocrystalline Amorphous metal

Nanocrystalline amorphous metal is produced by rapid quenching a molten alloy to produce a amorphous metal and then heat treating this alloy at higher than its crystallization temperature The alloy forms Nanocrystalline grain size of approximately 10 nm in the amorphous metal.


Annealing changes BH loops

M type material is done with no magnetic field applied during annealing

We produce H and L type BH loops by annealing with magnetic fields oriented either parallel or perpendicular to the ribbons surface.

Advantages are:

  • High saturation magnetic flux density, more than 1 Tesla 
  • High permeability over 10,000u at 100kHz
  • Excellent temperature characteristics. Very high Curie temperature (570°C) resulting in small permeability variation (less than +/-10%) at a temperature range of -40°C to 150°C.
  • Less affected by mechanical stress.  Because of the low magnetostriction permeability and core loss changes have very small changes.
  • Very low audio noise emission. Lower magnetostriction significantly reduces audible noise emission when the voltage and current applied to the core at audible frequency range.
  General Informational Brochure

Surge Absorbers beads and cores
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Our NANO amorphous tape-wound cores are used in (SMPS) Switched-Mode Power Supplies, Frequency Inverters, ASD and UPS and other applications for effective noise suppression caused by rapid changes in current. The high pulse permeability of these cores allow excellent performance in the suppression of reverse recovery current from the diode and ringing or surge current from switching circuit. The Surge Absorber Cores are normally used as single-turn choke or with very few turns

The saturation magnetic flux density is twice as high as that of Co-based amorphous metal and three times higher than that of Ni-Zn ferrite. The pulse permeability and the core loss are comparable to Co-based amorphous metal. As a result, a small core made of this material offers higher performance in suppression of surge current and voltage.

  These cores also feature low core losses and a very high squareness of the BH hysteresis loop resulting in a high inductance when the current crosses zero. This high inductance effectively blocks reverse recovery currents created by diodes. The material saturates at relative small currents. Thus, spike blocking is not possible at DC currents.
Toroidal type bead core


There are two types of beads leaded and non-leaded cores. These are used for low power and excellent performance in suppression of various kinds of current or voltage surge, such as the surge from a switching diode

Horizontal and vertical mounted leaded cores

  Download EMC brochure for information on beads:

File written by Adobe Photoshop� 4.0

Are used for medium and large power and are toroidally wound cores which show excellent performance for the suppression of various kinds of current or voltage surge, such as a surge from a switching diode.

Core range in size from outside diameters of 11 to 38mm and inside diameters of 4 to 22mm.

File written by Adobe Photoshop� 4.0 Download EMC components brochure

How amorphous ribbon is made
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The casting process

Ribbon is cast in widths up to 8 inches in wide and then is slit to width required for winding. Special winding machines wind the ribbon in to various Toroidal, Oval and C-core shapes. Cores then are further process via cutting, coating, annealing according to standard offering and customer requests.

Scott drawing from Meeting showing why Metglas is good choose: low losses.



For several years now, electronic watt-hour meters have more and more replaced the electromechanical Ferraris counters in the industrial world. Since their advantages are self-evident, it is now foreseeable, that domestic counters will also be substituted by electronic versions within the next decade.

The key component of an electronic watt-hour meter is a high-precision current transformer (CT) which isolates the whole device from the mains potential and provides the signal to be counted. By making use of modern high permeability materials like crystalline 80% NiFe of permalloy type (VACOPERM), Fe-based nano-crystalline VITROPERM or Co-based amorphous alloys (VITROVAC), the CT meets the requirements of phase and amplitude-error and linearity according the international meter standards ( e.g. IEC 61036, ANSI C12.xx) with and without DC tolerance in a very easy and economic way. Design support can be given with recommendations for core material, core size, number of



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