What are the maintenance details for the powdered iron core circuit board magnetic components?
2022-11-09
Components related to "magnetism" in circuit boards, including Permalloy core inductors, transformers, electromagnetic relays, contactors, Hall sensors, etc. This article will explain the maintenance methods for magnetic components on circuit boards.
1. Inductors
An inductor is a coil of conductor wound around an insulating frame. The insulating frame can be hollow, iron core, or magnetic core. In industrial control circuit board applications, a common use is to filter or store energy in switching power supplies. Various appearances of inductors.
One type of inductor is used to absorb high-frequency (above 50MHz) interference, called a ferrite bead. Another type of common-mode inductor is called a common-mode inductor, also known as a common-mode choke. It is a four-terminal device derived from a Permalloy core wound with two identical windings. Each set of coils is connected in series in the circuit. If there is a differential mode signal, the magnetic fluxes generated by the two coils will cancel each other out, and the coils will not impede the differential mode signal. When there is a common-mode signal, the magnetic fluxes generated by the two coils are enhanced, and the blocking effect of the coils on the signal is enhanced.
During the maintenance of industrial circuit boards, inductors are not easily damaged. Occasionally, there will be open circuits due to corrosion, burnout due to excessive current, and inter-turn short circuits. Open circuit damage can be measured with a multimeter resistance measurement. Inductance can be measured with an inductance tester. It is recommended to use a digital bridge to test the inductance. Since most energy storage inductors in power supply circuits operate at higher frequencies, above 10kHz, the frequency used when testing with a bridge is 10kHz. In addition to focusing on inductance, the test also focuses on the D value. The normal D value should be less than 0.1. If the D value is greater than 0.2, it is determined that there is an inter-turn short circuit in the coil.
2. Transformers
A transformer is a device that uses the principle of electromagnetic induction to change voltage. Common transformers on industrial control circuit boards are power frequency transformers using iron cores and switching transformers using Permalloy cores.
The basic characteristic of an ideal transformer is that the ratio of the input and output AC voltages is the same as the ratio of the number of turns of the input and output coils, so theoretically, the AC voltage can be arbitrarily increased or decreased.
Silicon steel core transformers are generally used in 50~400HZ power frequency applications. The magnetic flux density of silicon steel sheet cores is relatively large. Although the stacked silicon steel sheets are insulated by insulating paint, there are still eddy current losses in individual silicon steel sheets. This type of core is not suitable for high-frequency applications.
Permalloy core The resistivity of is much higher than that of metallic and alloy magnetic materials, so the eddy current loss is very small. Transformers made of Permalloy cores are used in high-frequency applications, such as energy storage inductors and switching transformers in switching power supplies. In addition, there are various new transformer core materials, such as Permalloy and amorphous nanocrystalline materials, which can balance permeability and eddy current loss.
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