What are the advantages of sendust cores?
When it comes to the selection of high-power inductor cores, the selection and comparison of magnetic cores, powder cores, sendust, and ferrite are questions that engineers often discuss. There are still many choices of cores for high-power inductors in the market. The available inductance materials are: sendust, iron powder core, sendust (silicon steel laminate), void ferrite, molybdenum and high magnetic Pass and so on. So what are their advantages?
Sendust and void ferrite
Sendust and void ferrite are commonly used raw materials for two ferrosilicon magnetic powder cores. In terms of softness and fullness, void ferrite must be planned in the safe zone of the descending curve. FeSi is planned to be in the range of the controlled descending curve, so that it can provide the fault tolerance characteristics, especially in high power hours.
In terms of magnetic flux comparison, set a specific 50% reduction planning point. The magnetic flux of sendust is more than twice that of void ferrite, which reduces the size of the magnetic core by 35%. The size of the magnetic core can be reduced during planning. 30% to 35% smaller.
The soft and full curve gives FeSi planning its own fault-tolerant ability, while the void ferrite does not.
The magnetic flux of ferrite can change with temperature, while FeSi remains relatively stable. Many ferrite suppliers or manufacturers may give the difference between the raw materials of the product in a different environment from 25% to 100%. Since the raw materials and results of sendust are different from void ferrite, there will not be many changes as the temperature changes.
In terms of marginal loss, ferrosilicon does not produce marginal loss, while interstitial ferrite has a large marginal loss. Some of the voids in the iron core will increase with the increase of temperature. Sendust also has gaps, but this is a uniform distributed gap. Because of this method, it will be very good in high-power applications.
Regarding the scale and energy storage, it can be seen from the comparison of the LI2 value of sendust and manganese-zinc ferrite that when the scales are all 55mm in size, 60μ is used for the test of sendust. In the condition of the size of sendust, The energy storage is about twice that of manganese-zinc-iron ferrite. When the energy storage is the same, the LI2 value is the same, and the sendust volume is reduced a lot. For planners, this effectively reduces the planning scale.
Void ferrite also has many advantages. Void ferrite can have a very high useful magnetic permeability μeff, ferrite can be above 500 and ferrite is now limited to μeff=125. The use of interstitial ferrite is more suitable for some low-power planning.
Sendust and iron powder core
In addition to accepting DC bias, switching regulator inductors also have certain AC current, usually 10kHz to 300kHz. This alternating current will generate a high-frequency magnetic field, causing core loss and causing the core to heat up. This situation will be reduced in sendust, so the inductance is more useful and the temperature is lower.
Sendust core loss is lower than that of iron powder core. Regarding the question of magnetoelasticity close to zero, sendust is very suitable for eliminating audio noise in filter inductors. Sendust is made without organic binders, so there is no doubt about thermal aging. All sendust cores can be operated successively at 200°C. In contrast, iron powder cores have magneto-elasticity.
Sendust and ferrosilicon
Special-grade ferrosilicon laminates are also used in large inductors, usually in the form of blocks or strips. The advantage of ferrosilicon is that the full magnetic flux density is higher. The iron-silicon shape (E, U, and I type cores) can also be used in large inductors with appropriate structures. Although ferrosilicon has a higher full magnetic flux density, ferrosilicon has more advantages, such as better soft fullness, low core loss, temperature stability and lower cost.
The ferrosilicon block has discrete voids, which are different from the distributed voids of sendust. Therefore, as the current increases, the fullness appears much faster. Sendust can take advantage of the full curve to design a smaller inductor.
Feature and application of sendust
Sendust is composed of aluminum-silicon-iron. It has a very high Bmax (1050tM). Its core loss is much lower than that of iron powder core and high magnetic flux. It has low magnetoelasticity (low noise) and is low The cost-effective energy storage material has no thermal aging and can be used to replace iron powder cores, and its function is very stable at high temperatures.
Sendust applications include power factor correction chokes, step-up/step-down regulators, DC output inductors and regression transformers.
Large sendust is used in high current (power) inductors, solar conversion, UPS uninterruptible power systems, hybrid cars, wind energy conversion and other high current applications.
There are two options for flat-type sendust, there are traditional square and round.
Relatively square, round has many advantages, such as reducing the volume of all inductors added due to winding, using the same number of turns to reduce the length of the winding wire, and minimizing DCR (direct current resistance). Copper loss reduces the cost of using copper wires and the cost of winding all inductors.
Sendust (flat plate type) has the characteristics of being used in high current planning, magnetic leakage is reduced to a very low level, better DC bias characteristics, outstanding heat dissipation and temperature stability, and high energy storage functions. Mounted on the PCB. Sendust (plate type) is used in DC/DC converters, high-current chokes, and central processing units in computers.
