What is the difference between an inductor and a magnetic bead?
2022.8.17
Articles
GOTREND Technology Co.,Ltd
GOTREND products, GBL series and GBD series are typical inductors and magnetic beads, which are very difficult to distinguish in the case of close appearance. Inductors and magnetic beads are similar in shape and function, and many people think that they are " Block AC , pass DC ", so that many people say that the two are confused. In fact, whether it is the principle or application, there is big difference between inductors and magnetic beads.
1、Differences between inductors and beads :
1.1 The magnetic materials of the inductor are open shield, and the magnetic field lines pass through the core and partly through the air; The magnetic material of the magnetic bead is closed, and almost all the magnetic field lines are enclosed in the magnetic ring, which is more "clean".
1.2 The unit of inductor is the inductance "Henry", and the unit of the bead is the impedance "ohm", which is generally the impedance value at 100MHz. One important thing is that even beads with the same parameters will vary greatly in filtering performance, because bead parameters mark the impedance of a particular frequency point, and even if the impedance of this frequency point is the same, the impedance at the frequency of other points will vary widely.
1.3 The impedance of the bead is the result of the joint action of the reactance "XL" and the resistance "RL", the low frequency "X" dominates, the high frequency "R" dominates, and the inductor is mostly used in the low frequency band (under 50MHZ), and the bead is mostly used in the high frequency filtering application, "R" will absorb noise and convert to heat, so the bead unit is "Ohm".
1.4 The filtering principle of inductor is to convert electrical energy into magnetic energy, and then re-convert magnetic energy into electrical energy (noise) or radiation (EMI), while magnetic beads convert electrical energy into thermal energy, and magnetic beads are more "clean" filter elements
1.5 The inductor is an energy storage element that may self-excitate with the capacitor during filtering, while the bead is the energy-consuming element "R" and doesn't self-excitate when working in conjunction with the capacitor.
1.6 Inductor and bead are both has rated current parameters, the difference is when the current exceeds the rated current, the effective inductance value of the inductance will decrease, and the bead may be directly burned.
1.7 From the level of EMC (electromagnetic compatibility), because the bead can convert high-frequency noise into thermal energy, it has a very good anti-radiation function, is a commonly used anti-EMI device, commonly used with the user interface signal filtering, power filtering, etc.
1.8 Both the bead and the inductor have a DC resistance, and the DC resistance of the bead is smaller than that of the inductor with the same filtering performance, so the voltage drop on the bead is smaller when used for power filtering.
2、 The common point with inductor and bead
2.1 Rated current.
When the inductor's rated current exceeds its rated current, the inductance value will decrease rapidly, but the inductor device may not be damaged; When the operating current of the bead exceeds its rated current, it will cause damage to the bead.
2.2 DC resistance.
When used in the power supply circuit, there is a certain current on it, and if the DC resistance of the inductor or the bead itself is large, a certain voltage drop will be generated. Therefore, in the selection, it is required to select a device with a small DC resistance.
2.3 Frequency characteristic curve.
Manufacturer profiles for inductors and beads are accompanied by a curve of the device's frequency characteristics. In the selection, these curves need to be carefully referenced to select the appropriate device. When applying, pay attention to its resonant frequency.
3、Conclusion
In conclusion, the inductor works in the frequency band where the impedance is much greater than the resistance, and the reactance is mainly the inductive reactance, and its unit is the inductance "H". Since the main component of the reactance component is very small, all inductors are mainly the role of energy storage. The bead mainly works in the frequency band where the resistance is greater than the reactance, and the resistance accounts for the main component, so the unit of the bead is ohms.
Due to the small amount of reactive characteristic, very little energy storage, all we say that the beads are mainly consumed by resistance heating, when selecting the beads, we must put the target in the high-frequency band, and selects the beads according to the impedance frequency curve of the beads and the target noise.
The above are some cases of inductor heating problems for reference only, because different cases are different and need to be analyzed specifically.
Related articles :
• APPLE MagSafe tangle dancing with Qi2 MPP
• What is copper loss? What is the skin effect ? The difference between Isat and Irms
• What is an inductor?
