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Characteristics of amorphous common mode inductors

by:Catech      2023-04-13

Both the common mode inductor and the spike suppressor are in the small signal working state, and the larger the inductance is required, the better. The inductance L is proportional to the effective magnetic permeability μe, and the iron core of the same specification, the higher the μe, the larger the L. Therefore, the use of ultra-microcrystalline alloy materials to make common-mode inductor cores can greatly reduce the size of the core, especially for common-mode inductor cores under high-current and high-power conditions. It has good cost performance and replaces ferrite cores. . Generally, the effective magnetic permeability of this type of ferrite is about 10,000, while the effective magnetic permeability μe of ultramicrocrystalline alloy can be 80,000 to 100,000. Under the same requirement of inductance, the size of the latter magnetic core is only 1/8 to 1 of the former. /10, the unit price difference between the two is about 4 to 5 times, obviously ultrafine-crystalline alloys are more competitive. For example, in a certain three-phase switching power supply with a working current of 100A, one Φ130×Φ90×Φ30 mm ultramicrocrystalline alloy core replaces four Φ130×Φ70×Φ50 high-performance ferrite cores.

Spike suppressor is a common anti-noise component in switching power supply. The inductor in this device is small in size and large inductance, so the magnetic core material is required to have high magnetic permeability. In the past, it was made of Co-based amorphous alloy. Due to high Co content, high price and difficult application of this kind of small inductance devices, ultramicrocrystalline strips are now used instead of Co-based amorphous alloys to make such small inductance series iron cores, which greatly reduces the cost.

Advantages of amorphous inductors compared to ferrite inductors:

(1) Due to the low power consumption of the iron-based nanocrystalline alloy, the allowable working magnetic density is higher than 200mT. The cross section and volume of the iron core are reduced, the number of coil turns is reduced, the amount of copper and iron used in the medium and high frequency electronic transformer will be reduced, and the overall cost will be reduced.

(2) The use temperature of iron-based nanocrystalline alloy is high, and the electromagnetic wire with high temperature index can be used for medium and high frequency electronic transformers. The volume of the transformer and the amount of copper and iron used can be further reduced.

(3) For high-power medium-frequency electronic transformers above 1kW, soft magnetic ferrite has low magnetic density and large core volume. Under the existing production process conditions, it is difficult to manufacture large-scale iron cores, the yield is low, and the cost is not lower than that of Iron-based nanocrystalline alloys are low.

(4) For low-power medium and high-frequency electronic transformers below 20W, the weight and volume of the iron core itself are not large, and the increased cost of using iron-based nanocrystalline alloys accounts for a small proportion of the overall cost of the iron core.


1. Made of cobalt-based amorphous alloy or iron-based nanocrystalline strip

2. High magnetic permeability and low coercive force—increase the insertion loss of the device, improve the efficiency, and enhance the common mode noise suppression effect

3. Good frequency characteristics - good suppression of common mode noise in a wide frequency range

4. Good temperature stability - can work for a long time at -55~130°C

Magnetic Properties of Ultramicrocrystalline Alloy Common Mode Inductor

1: Specific application of amorphous ultramicrocrystalline common mode inductors:

Common-mode inductors made of ultrafine-crystalline alloys are widely used in DC-DC converters, filter resonance suppressors, communication power filters, etc.;

Amorphous common-mode inductor: It can achieve constant inductance characteristics and anti-superimposed DC bias capability through two methods: no air gap and open air gap, and the loss is small. Anti-DC filter widely used in car audio

2: Electrical characteristics of amorphous ultramicrocrystalline common mode inductors:

High magnetic permeability, high saturation magnetic flux density, low eddy current loss, good broadband characteristics and temperature characteristics, etc. These excellent properties reduce the number of coil turns, small size, high inductance, thus reducing copper loss and winding capacity, so nanometer The crystal series EMC common mode filter has the characteristics of no resonance insertion loss in a wide frequency range, and can be used as a common mode filter inductor for communication sources, common mode filter for frequency conversion air conditioners, etc.

【Amorphous Magnetic Ring】Typical application:

(1) Used for AC filtering and common mode interference suppression inductance core in switching power supply

(2) Used as DC high-frequency carrier filter inductor in car audio

(3) Used for frequency conversion air conditioner power factor correction inductor PFC core, anti-EMC circuit common mode inductor magnetic ring, differential mode inductor core

(4) Leakage protection coils for personal electric shock protection for water heaters, zero-sequence current transformer cores

(5) It is used to measure the magnetic core of current transformer for various instruments and meters, and precisely detect the magnetic core of zero-sequence current transformer

Most people who see a in operation for the first time are amazed at how well the coilcraft common mode choke is managed.
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