Nanocrystalline Soft Magnetic Material FINEMET®
FINEMET® Common mode chokes with high permeability, low Q-factor and stable temperature chracteristics, that realize effective noise suppression and contribute to size and weight reduction for your applications.

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EMC/EMI components
Comon Mode Choke

EMC/EMI components
Comon Mode Choke

EMC/EMI components
Comon Mode Choke

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  • Note: Standard product sample for automotive applications and special applications is only for initial evaluation purposes.
  • Inquiries for automotive applications, special applications, and customization, please contact us by the inquiry form below.

Soft Magnetic Materials and Components (for FINEMET® Applied Product and Ribbon)

What is FM (FINEMET®)?

Conventionally, it was thought that "the larger the crystal grain size of a crystalline soft magnetic material, the better the soft magnetic properties, and the smaller the crystal grain size, the worse the soft magnetic properties." We have discovered that reducing the crystal grain size to the nanometer order dramatically improves the soft magnetic properties.
The nanocrystalline soft magnetic material "FINEMET®" is a material that overturns conventional wisdom and achieves high soft magnetic properties.

What is the raw material of FM (FINEMET®)?

The main ingredient is Fe, Si (silicon), B (boron), and trace amount of Cu (copper) and Nb (niobium).

Can I purchase FM (FINEMET®) material?

FINEMET® is sold both as ribbons and as applied products (cores, coils, and sheet products) after processing.

The material of FINEMET® is called FINEMET® ribbon.
FINEMET® ribbon is in an amorphous state, so in order to obtain the magnetic properties listed in the catalog, it is necessary to do heat treatment for crystallization.
Does the performance of FM-CMC (FINEMET®-Common Mode Choke Coil) change depending on the operating temperature environment?

FINEMET®'s magnetic permeability is characterized by a little change due to temperature changes.
Stable performance over a wider temperature range than CMC using ferrite.

What is the usable temperature range for FM-CMC (FINEMET®-Common Mode Choke Coil)?

The general recommended operating temperature ranges is from -40 degrees to 130 degrees.

What is CMC (common mode choke coil)?

A common mode choke coil has the same winding ratio on the primary and secondary sides (𝐿1=𝐿2) , and the winding polarity (winding direction) is the same. A coil used to reduce common mode noise in electrical circuits.

What are the main usage of FM-CMC (FINEMET®-Common Mode Choke Coil)?

Used as power sources for air conditioners, pumps, general-purpose inverters, various inverter devices, communications equipment, medical equipment, etc.
In recent years, it has been widely used in xEV in-vehicle inverters, in-vehicle power supplies, alternative energy power conditioners, etc.

In what frequency range is FM-CMC (FINEMET®-Common Mode Choke Coil) effective?

FINEMET®-Common Mode Choke Coils are designed for effective noise reduction over a wide range of frequencies. It is effective in the range of several tens of kilohertz (kHz) to several tens of megahertz (MHz).

What are the advantages of FM-CMC (FINEMET®-Common Mode Choke Coil) compared to CMC made of other materials?
  1. 1It is effective over a wide frequency range from tens of kilohertz (kHz) to tens of megahertz (MHz).
  2. 2It can be designed in a relatively small size while still being highly effective. This allows it to be incorporated into circuits and equipment with space constraints.
  3. 3It exhibits excellent noise reduction effects even in environments as low as -40℃ and as high as 130℃.
What kind of product is a choke coil?

An element used in electrical circuits, also called an inductor or reactor. It is an electrical circuit component that passes current with a frequency lower than the target frequency and blocks current higher than the target frequency.

There are two types of choke coils which are common mode chokes and normal mode (differential) chokes. They are used to counter common mode noise and normal mode noise, respectively.
What is common mode noise?

Common mode noise is noise that occurs between the power line and ground. Noise current occurs in the same direction on the + side and - side of the power line, causes a ground fault through the capacitance component of the wire, and returns via the ground. Since it is a noise generated between the line and the ground, it cannot be expected to be attenuated by resistance and has the property of affecting far away.

What is normal mode noise?

Normal mode noise is noise that occurs between power lines. Noise currents occur in different directions on the + and - sides of the power line. It will be easier to understand that it is going out from the + side line and coming back through the - side line.

What are the conditions when selecting a CMC (common mode choke coil)?
  1. 1Rated Current: Must have an appropriate current rating (usually the maximum allowable current).
    Select the coil current rating considering the maximum current expected in the circuit.
    The temperature of a common mode choke coil is generally determined by the relationship between the coil's heat capacity, DC resistance, and current loss.
  2. 2Impedance: Choose a coil with high impedance in the frequency range of the noise you want to counteract.
    The relationship is “impedance (Ω) = inductance (H) x frequency (Hz) x 2 x π”.
    As a performance index, it is sometimes explained using impedance and sometimes using inductance, but there is no problem in thinking that they are talking about the same thing.
  3. 3Rated temperature: Coil insulation is maintained by insulating resin and electric wire.
    Each coil in the catalog has the rated temperature and temperature rise at rated current (reference value) according to the materials used, such as insulated resin, electric wire, etc, so please select a coil within the range of “operating environment temperature + temperature rise < rated temperature”.
    The temperature rise at rated current (reference value) is the value in a specific test environment, so be sure to check the temperature rise in the mounting environment.
  4. 4Size constraints: The size and shape of the coil must be selected appropriately.
What phenomenon does CMC (common mode choke coil) cause magnetic saturation?

CMC has a structure in which a winding (coil) is attached to a core made of soft magnetic material, and when current attempts to flow through the coil, magnetic flux is generated within the core, which functions to suppress changes in the current. The amount of magnetic flux that can be induced in the coil (total magnetic flux) is determined in proportion to the magnetic property called saturation magnetic flux density (Bs), the cross-sectional area of the core, and the turns of the coil. Magnetic saturation of CMC means that the magnetic flux density within the core reaches the saturation magnetic flux density. When magnetic saturation occurs, it is no longer possible to induce magnetic flux, so it is no longer possible to suppress noise current.

There are various causes of magnetic saturation, but the following are generally considered.
  • 1)  Unbalanced magnetization due to unbalanced current: In principle, the current flowing in the + side and - side wires are the same, but when a difference occurs in the current for some reason.
  • 2)  Pulse noise, etc.: The noise level is too high and magnetic saturation occurs.
What is the effect of CMC (common mode choke coil)?
  1. 1Removal of common mode noise: CMC plays the role of preventing common mode noise from flowing into the power line.
  2. 2Reduction of EMI (Electromagnetic Interference): CMC also has the effect of reducing electromagnetic interference (EMI) generated within the circuit. EMI is a phenomenon in which electromagnetic waves emitted by electronic devices affect other devices.
What principle does FM-CMC (FINEMET®-Common Mode Choke Coil) use to remove noise?

CMC has a structure in which a winding (coil) is attached to a core made of soft magnetic material, and when current attempts to flow through the coil, magnetic flux is generated within the core, which functions to suppress changes in the current.
In a CMC using a ferrite core, the impedance R component is low, so noise energy is stored in the CMC and then emitted in a different frequency band, but in a CMC using an FM core, the impedance R component is large. Since the noise energy is consumed in the coil, it has a great noise attenuation effect.

What are the design considerations to maximize the effectiveness of FM-CMC (FINEMET®- Common Mode Choke Coil)?
  1. 1Selection of impedance: The impedance of the coil has a great effect on noise removal. It is necessary to understand the frequency range of common mode noise and select a coil with high impedance at that frequency.
  2. 2Installation position and wiring: Noise can be effectively removed by placing the coil close to the noise source.


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