Permalloy magnetic ring, amorphous, ultrafine crystal (nanocrystalline) iron core (marketing department of Shanghai HY Industry Co., Ltd)
1，Introduction of various permalloy magnetic ring, amorphous and ultrafine (nanocrystalline) iron cores
Performance characteristics: Permalloy metal core: Various Permalloy materials have their own differences, which are superior to silicon steel materials and ferrite in typical magnetic properties, and have higher temperature stability and aging stability. High initial magnetic permeability High rate permalloy material (1j79, 1j85, 1j86) iron cores are often used to make current transformers and small signal transformers; high rectangularity permalloy material (1J50, 1j51) iron cores are often used to make magnetic amplifiers and dual-stage pulse transformers ; Low remanence Permalloy material (1j67h) iron core is often used to make small and medium power unipolar pulse transformers. Amorphous core:
Iron-based amorphous iron core: It has a high saturation magnetic induction (1.45-1.56t) in almost all amorphous alloy iron cores, and has high magnetic permeability, low coercive force, low loss, low excitation current and Good temperature stability and aging stability. Mainly used to replace silicon steel sheets, as various forms, different power frequency distribution transformers, intermediate frequency transformers, working frequency from 50hz to 10khz; as a high-power switching power supply reactor core , the use frequency can reach 50khz.
Iron-nickel-based amorphous iron core: medium to low saturation magnetic induction (0.75t), high magnetic permeability, low coercive force, wear resistance and corrosion resistance, good stability. It is often used to replace permalloy iron core as leakage switch The zero-sequence current transformer core in.
Cobalt-based amorphous iron core: It has high magnetic permeability among all amorphous alloy iron cores, and has medium to low saturation magnetic induction (0.65t), low coercive force, low loss, and excellent durability Abrasion and corrosion resistance, good temperature stability and aging stability, shock and vibration resistance. Mainly used to replace permalloy iron core and ferrite iron core to make high-frequency transformers, filter inductors, magnetic amplifiers, pulse transformers, Pulse compressors and other applications in the field of high-quality high-frequency power supply equipment (especially military equipment)
Microcrystalline magnetic core: high saturation magnetic induction (1.1~1.2t), high magnetic permeability, low coercive force, low loss and good stability, wear resistance, corrosion resistance, and low price, Among all metal soft magnetic material cores, it has excellent cost performance, and the material used to make microcrystalline iron core is known as “green material”. It is widely used to replace silicon steel, permalloy and ferrite, as various forms High-frequency (20khz100khz) switching power supply for large, medium and small power main transformers, control transformers, wave inductors, energy storage inductors, reactors, magnetic amplifiers and saturable reactor cores, emc filter common inductance and differential mode inductor cores , idsn miniature isolation transformer core; also widely used in various transformer cores of similar precision.
Permalloy magnetic ring specification range:
Magnetic core maximum outer diameter: 750mm
Magnetic core minimum inner diameter: 6mm
The width of the smallest piece of magnetic core: 5mm
Maximum core width: 40mm (can be stacked to get wider)
Other specifications can be customized according to customer needs
Permalloy magnetic ring Reference instructions:
Electromagnetic properties of permalloy metal cores, amorphous and microcrystalline cores:
Transverse magnetic heat treatment, low br, has certain constant conduction characteristics, suitable for low-power unipolar pulse transformers, single-ended switching power supply transformers, filter inductors, reactors;
Conventional heat treatment, low pc, extremely low excitation current; suitable for medium frequency transformers;
Longitudinal magnetic heat treatment, high br, suitable for distribution transformers, intermediate frequency transformers, double-ended switching power supply transformers, high-power bipolar pulse transformers, saturable reactors and pulse compressors.
2,Application of Amorphous and Ultrafine Crystalline Materials
Magnetic material 120×60×40 magnetic core. according to
In the formula: bm——Working magnetic induction intensity, generally selected at bs/2
Appropriate, both bm choose 0.8t;
e——AC input voltage, v;
n – the number of primary turns;
f——AC input voltage frequency, hz;
sc – the effective cross-sectional area of the magnetic core, cm2.
And because sc=(1/2)×d×(r－r)×h(2)
In the formula: d – the duty factor of the magnetic core, generally 0.65;
r——diameter of the outer ring of the magnetic core, cm;
r——the diameter of the inner ring of the magnetic core, cm;
h – the height of the magnetic core, cm.
So sc=(1/2)×d×(r-r)×h =(1/2)×0.65×(12-6)×4 =7.8cm2
From formula (1) can get: n== =198 turns Considering the copper loss, n chooses 200 turns.
In order to verify whether the magnetic permeability μe is within the range of the core material parameters when n=200 turns, the formula (3) n=104×(3) can be used
In the formula: l——primary inductance, h;
lc—the average magnetic path length of the magnetic core, cm.
l is calculated as follows:
Before winding into a transformer, the primary inductance cannot be measured, but it can be deduced from formula (4). = (4)
That is, you can wind n1=10 turns first, and measure l1=13mh, so when n=200 turns, you can get l=l1×=13×=5.2h
From formula (3), it can be obtained that μe=×108=×108 =4×104
μe meets the requirement of μi=8×104. It shows that the design of primary turns of transformer is reasonable.
The number of secondary turns can be obtained from the transformation ratio of voltage and turns, which will not be repeated here.
After experiments, this theoretical calculation can carry a 1kw load, and the work is stable and reliable.
3) Points to pay attention to when designing
The value of bm cannot be selected too high. Due to the dispersion of the magnetic core parameters, the inductance under the same number of turns is different, and the difference is large. If the bm is too high, it is easy to saturate the magnetic core.
How to judge that the magnetic core has entered saturation?
In the shallow saturation state, the primary voltage is increased, the secondary voltage does not increase, and all the increased energy is lost by the magnetic core; after the load is increased, the output voltage drops rapidly, the load capacity decreases, and the energy is lost by the Permalloy magnetic ring magnetic core .
In the deep saturation state, the magnetic core will be very hot if the primary voltage is less than 220v, and the primary voltage will increase again, the secondary voltage will not change, and all the energy will be lost by the magnetic core.
3,Permalloy magnetic ring Magnetic cores for switching power supplies
3.1 Magnetic cores for single-ended converters
The single-ended converter mainly requires low residual magnetic induction of the magnetic core, that is, the br/bs is small.
The magnetic core is made of iron-based ultrafine crystal low remanence material (br/bs≤0.2), the saturation magnetic induction bm=1.2t, the remanence br<0.2t, the initial permeability μi>2×104, and the maximum permeability Rate μm=5×104, loss p0.35 (10khz) <18w/kg.
This is because the core of the single-ended converter works in the first quadrant of the hysteresis loop, and has a large δb (δb=bm-br) for the material, and the saturation magnetic induction bm of the iron-based ultrafine crystal material =1.2t, no matter what kind of magnetic field treatment it undergoes, it will not change, so to increase δb, only a low br core is used. Especially for the single-ended flyback main transformer, sufficient saturation magnetic induction bm and suitable magnetic permeability are required. Because the main transformer in the single-ended flyback circuit requires energy storage, the amount of coil energy storage depends on two factors: one is the working magnetic induction be or inductance l of the material; the other is the working magnetic field hm or working current i. Energy storage w=li2, under a certain current, the magnetic core cannot be saturated. The saturation magnetic induction bm is determined by the material, and the low br magnetic core is conducive to constant magnetic permeability, so that the magnetic core is not saturated under a certain current.
3.2 Magnetic cores for full-bridge, half-bridge, and push-pull converters
For this kind of double-ended converter, the saturation magnetic induction bm of the magnetic core is mainly required to be high.
Although the saturation magnetic induction intensity bm of iron-based amorphous materials is high, because the working frequency of iron-based amorphous materials is low (<15khz), when the frequency is high, the loss increases, so it is not suitable for inverter power supplies above hundreds of khz of. The magnetic core is made of remanence (br/bs≤0.6) material in iron-based ultrafine crystal. Saturation magnetic induction bm=1.2t, initial permeability μi>8×104, maximum permeability μm=45×104. Loss p0.3/(100khz)<300w/kg, high working frequency.
Because the transformers in the full bridge, half bridge, and push-pull converters work at both ends, the requirements for br are not very strict, and what it needs is 2bm. However, if a high br magnetic core is selected, saturation is likely to occur when the power supply is large. For this reason, for medium and high-power switching power supplies, medium-br magnetic cores can be used, which can also make the transformer have a certain inductance. Especially for a resonant power supply, a certain transformer inductance can act as a resonant inductance to make the full bridge, half bridge, and push-pull circuits resonate, and achieve the function of zvs or zcs soft switching.
However, for some high-power switching power supplies, in order to prevent bias magnetization, low remanence (low br) cores are also used.
4 Permalloy magnetic ring Magnetic cores for choke coils
The magnetic core for the choke coil requires a certain amount of energy storage, so materials with low remanence and transverse magnetic permeability should be used.
Using iron-based amorphous low remanence (low br) material core, saturation magnetic induction bm=1.5t, remanence br<0.1t, constant permeability 250~1200.
The choke coil is an inductive element that prevents AC components and only allows DC to pass through, so the magnetic characteristics when DC and AC currents are applied to the core, that is, the DC bias characteristics are very important. Specifically, the inductance should be such that the DC current does not easily saturate the core, but is large enough for the AC component. For this reason, high saturation magnetic flux density bm and constant magnetic permeability are required as material characteristics.
5 Amorphous saturable magnetic core
The saturated magnetic core mainly regards the magnetic core as a “magnetic switch”. When the magnetic core is not saturated, the inductance is large, which is equivalent to the magnetic switch being disconnected; when the magnetic core is fully saturated, the inductance is small, which is equivalent to the magnetic switch short circuit. .
Using cobalt-based amorphous alloy core, it has the characteristics of high magnetic permeability, low coercive force, high moment ratio (bs/br), low loss and so on. Saturation magnetic induction bm=0.5～0.8t, coercive force hc<2a/m.
1) Self-saturated reactor
The self-saturation reactor hopes that the magnetic core will be a switch with a fast response, and a little current will quickly saturate the magnetic core. Therefore, high remanence (high br) materials should be used, initial magnetic permeability μi>5×104, maximum magnetic permeability μm>25×104, loss p0.5 (20khz)<35w/kg. It is mainly used to eliminate the secondary parasitic oscillation of the switching power supply, eliminate the peak, etc.
2) Saturable reactor
The saturable reactor uses the huge difference between the unsaturated and saturated magnetic permeability of the magnetic core to delay the current to obtain a preset time. At this time, the pulse transmitted by the pulse transformer can be compressed, and the pulse width can be adjusted according to the magnitude of the current, so that the output voltage can be changed. Utilizing this feature of the saturable reactor, multi-channel regulation can be realized. Because the switching power supply with general pulse width adjustment can only adjust the pulse width of one group of outputs and change the output voltage, but cannot adjust the output voltage of several channels. Using saturable reactors, each channel can be controlled by potentiometers. The current of the output circuit is used to change the pulse width of each circuit, so as to realize multi-channel regulation. Now foreign countries have made circuits that can adjust more than a dozen outputs through potentiometers.
Therefore, the saturable reactor should select the magnetic core according to the size of the current and the compression of the output pulse width. For example, if a certain pulse compression is required under high current, a low remanence (low br) core should be used. In short, specific problems should be analyzed in detail.