Nanocrystalline, also known as nano-amorphous, is a new type of magnetic material. Nanocrystalline cores are favored by people for their high magnetic permeability, high squareness ratio, low core loss and high temperature stability.
The Nanocrystalline core has high saturation magnetic induction (1.l~1.2T), high magnetic permeability, low coercivity, low loss and good stability, wear resistance and corrosion resistance. The low price has the best price/performance ratio among all metal soft magnetic material cores. The material used to make the Nanocrystalline core is known as the “green material” and is widely used to replace silicon steel, permalloy and ferrite as large, medium and small in various forms of high frequency (20-100 kHz) switching power supplies. Power main transformer, control transformer, wave inductor, energy storage inductor, reactor, magnetic amplifier, saturated reactor core, EMC filter common mode inductor and differential mode inductor core. IDSN miniature isolation transformer core is also widely used in various types of transformer cores of the same precision.
1 main features of Nanocrystalline core
The VITROPERM 500F iron-based Nanocrystalline core has the following features:
1) Very high initial permeability, μ = 30 000 ~ 80 000, and the magnetic permeability varies very little with the flux density and temperature;
2) The core loss is extremely low and does not change with temperature in the range of 40 to +120 °C;
3) Very high saturation flux density (Bs = 1.2T), allowing a lower switching frequency to be selected, which can reduce the cost of switching power supplies and EMI filters;
4) The magnetic core is encapsulated by epoxy resin, which has high mechanical strength, no hysteresis and stretching, and can withstand strong vibration;
5) It can replace the traditional ferrite core to reduce the volume of the switching power supply. Improve reliable parts.
2, the application of Nanocrystalline magnetic core in switching power supply
2.1 Application of Nanocrystalline core material in high frequency transformer
At present, high frequency transformers generally use ferrite cores. Comparing the performance of the VITROPERM 5OOF iron-based ultra-micronized magnetic core with the N67 series ferrite core produced by two German subsidiaries, the magnetic permeability of the Nanocrystalline core changes much less with temperature than the ferrite core. It can improve the stability and reliability of the switching power supply. When the temperature changes, the loss of the Nanocrystalline core is much lower than that of the ferrite core.
In addition, the ferrite core has a low Curie point temperature and is easily demagnetized at high temperatures. If a super microcrystalline core is used to make a transformer, the amount of change in magnetic induction during operation can be changed from O. 4T increased to 1. OT, the operating frequency of the power switch tube is reduced to below 100 kHz.
2.2. Application of Nanocrystalline core in common mode inductor
When a common mode inductor (also known as a common mode choke) is fabricated using an ultrafine crystal core, a large amount of inductance can be obtained by winding a small number of turns, thereby reducing copper loss and saving wire and reducing The volume of the common mode inductor is small. Common mode inductors made with Nanocrystalline cores have high common-mode insertion loss and suppress common-mode interference over a wide frequency range, eliminating the need for complex filter circuits. A common mode inductor is fabricated by using a ferrite core and an Nanocrystalline core, respectively.
2.3. Application of Nanocrystalline core in EMI filter
The cobalt-based Nanocrystalline core VIT-ROVAC 6025Z produced by VAC can be widely used in the EM1 filter of switching power supply, which can effectively suppress the spike voltage generated by the rapid change of current. A spike suppressor can be fabricated by winding one or several turns of copper wire on the Nanocrystalline core. The structure is very simple and the suppression of noise interference is very good. The VITROVAC 6025Z Nanocrystalline core has a very low core loss and a high squareness ratio. When the current suddenly changes to zero, it exhibits a large inductance, which can hinder the reverse current of the rectifier.
When the current is turned on, the core is in a saturated state and has a very low inductance. When the current reaches the operating point (remanence point)
when the current is turned off, the current continues in the negative direction due to the reverse recovery time of the rectifier. Reduced, but the Nanocrystalline core has a very high magnetic permeability, which will present a large amount of inductance, so it does not go through the theoretical operating point (should correspond to the moment when the reverse peak current IR occurs). It is directly to the working point (ie, the reverse remanent point), and then magnetized to start another cycle. This characteristic of suppressing the peak current of the rectifier is called “soft recovery.”
With the development and maturity of power electronics technology, people gradually realize that magnetic components are not only functional components in power supplies, but also their volume, weight and loss account for a considerable proportion in the whole machine. According to statistics, the weight of the magnetic component is generally 30% to 40% of the total weight of the converter, and the volume accounts for 20% to 30% of the total volume. For the high-frequency power supply of modular design, the proportion of the volume and weight of the magnetic component It will be even higher. In addition, magnetic components are an important factor affecting the dynamic performance of the power supply output and output ripple. Therefore, in order to improve the power density, efficiency, and output quality of the power supply, in-depth research should be conducted to reduce the volume, weight, and loss of the magnetic component to meet the needs of power development. We have reason to believe that Nanocrystalline cores will have a very broad application prospect in switching power supplies.