Characteristics of chip ferrite inductors
SMD ferrite inductance is a kind of chip inductor, and the parameters of ferrite inductance are also different from ordinary wirewound inductors, ordinary wirewound inductors are based on the size of the inductance to evaluate the inductance of the inductance on the AC signal, and the ferrite inductance is evaluated by how much the high-frequency signal is absorbed after passing through the ferrite inductor, or a specified frequency signal after passing through the ferrite inductor, the suppression of the signal is equivalent to how much equivalent resistance is connected in series in the loop. Therefore, the evaluation of the inductance performance of ferrite is not the amount of inductance, but the resistance at a certain frequency, which is measured in ohms.
SMD ferrite inductors.
Different grades of SMD ferrite inductors have different resistance values at the same frequency, and the same grade of ferrite also has different resistance values at different frequencies. These can generally be found in product specifications. In practice, we also select the ferrite inductor based on the operating frequency range in the circuit and the size of the frequency signal we want to suppress.
The inductance is determined, but what about the package sizeTaking the ferrite magnetic ring inductor as an example, the selection of the package size of the ferrite magnetic ring inductor: when the material is determined, the larger the volume of the ferrite, the better the suppression effect;When the volume is constant, the impedance of the long and thin shape is greater than that of the short and thick shape, and the suppression effect is betterThe larger the cross-sectional area of the ferrite, the less saturated it is, and the greater the bias current it can withstandThe smaller the inner meridian of the ferrite, the better the inhibition effect.
Characteristics of chip ferrite inductors
1. Small size;
2. Small magnetic flux leakage, no coupling, high reliability;
3. No lead, no tracking, suitable for high-density surface mounting;
4. Excellent solderability and thermal shock resistance, suitable for wave soldering and reflow soldering
Generally, there is no problem with the quality of the newly purchased transformer, and it can be used directly without testing, but the maintenance of the transformer should be well understood. Of course, there are many types of transformer failures, but it is essential to understand these three types of faults:
1. Transformer insulation breakdown.
The main causes of transformer insulation breakdown come from three sources: moisture, foreign objects, and lightning strikes. When there is water in the transformer bushing, oil conservator and explosion-proof cylinder, the breakdown strength of the transformer insulation is reduced, and then a local short circuit occursWhen foreign substances such as conductors, dust, and impurities remain in the transformer, discharge or wear will occur under normal voltage, which will cause the insulator to break downWhen the transformer is suddenly attacked by lightning, the high current will cause the weak parts of the transformer insulation to break down, resulting in a short circuit.
2. Transformer overheating fault.
Transformer overheating is usually caused by abnormal currents. As a rule of thumb, eddy currents, circulating currents, increased resistance, and heat dissipation obstruction can cause transformer overheating. If the overheating is not effectively treated, it will affect the normal operation and performance of the transformer. Sustainable development will lead to grid safety issues, accompanied by transformer fires.
3. Transformer short circuit accident.
The transformer is affected by factors such as aging, vibration and environmental drastic changes in operation, and single-phase grounding, two-phase short circuit, two-phase short circuit and three-phase short circuit accidents will occur, and the first port short circuit is the most serious short circuit accident, which seriously affects the safe operation of the transformer.