The three-pin inductor is an electronic component applied to the circuit using surface mount technology. Its appearance structure usually consists of three parts: magnetic core, coil, and pin. Two of the coils are located on the same magnetic core, while the third wire is independent of the other two coils.
This structure enables the three-pin inductor to achieve electrical isolation of the signal and ensure the stability of the signal transmission quality.
The three-pin inductor, also known as the autotransformer, is a transformer with only one winding. When it is used as a step-down transformer, a part of the turns are extracted from the winding as the secondary winding; when it is used as a step-up transformer, the external voltage is only applied to a part of the turns of the winding. A notable feature of this transformer is that the part of the winding that belongs to both the primary and secondary is called the common winding, and the rest is called the series winding.
Compared with ordinary transformers, autotransformers of the same capacity are not only small in size, but also highly efficient. The larger the transformer capacity, the higher the voltage.
In addition, autotransformers also have significant advantages such as large capacity, low loss, and low cost. Therefore, with the development of power systems, the increase in voltage levels and the increase in transmission capacity, they have been widely used.
Compared with ordinary double-winding transformers, autotransformers have the following main features:
(1) Since the calculated capacity of the autotransformer is less than the rated capacity. So under the same rated capacity, the main dimensions of the autotransformer are smaller, and the effective materials (silicon steel sheets, wires) and structural materials (steel) are also reduced accordingly, thereby reducing the cost. The reduction of effective materials also reduces copper loss and iron loss accordingly, so the efficiency of the autotransformer is higher. At the same time, due to the reduction of the main dimensions and weight, a single transformer with a larger capacity can be manufactured under acceptable transportation conditions. But generally in autotransformers, the above advantages are only obvious when k≤2.
(2) Since the short-circuit impedance of the autotransformer is smaller than that of the two-winding transformer, the voltage change rate is smaller, but the short-circuit current is larger.
(3) Since there is a direct electrical connection between the primary and secondary windings of the autotransformer, when an overvoltage occurs on the high voltage side, it will cause a serious overvoltage on the low voltage side. Lightning arresters must be installed on both the primary and secondary windings. Do not assume that the primary and secondary windings are connected in series. To avoid this danger, the primary winding has been installed and the secondary winding can be omitted.
(4) In general transformers, the on-load voltage regulator is often connected to the grounded neutral point, so that the voltage level of the voltage regulator can be lower than that of the line-end voltage regulator. However, the neutral point voltage regulation side of the autotransformer will bring about the so-called related voltage regulation problem. Therefore, when the autotransformer is required to perform on-load voltage regulation, only the line-end voltage regulation method can be used.
Working principle of three-pin inductor：
1. Transformer method
The input voltage and output voltage are changed by the winding ratio of the three-pin inductor to achieve the effect of voltage transformation and isolation.
2. Filtering method
The three-pin inductor can play a certain filtering role in the circuit, so that the signal is isolated and weakened when passing through.
3. Weak current signal processing
The three-pin inductor has a good performance in some weak current signal processing circuits, which can play the role of isolation, amplification, and voltage stabilization, making the signal transmission more stable.
Application of three-pin inductor: used in lamps and automotive products. High efficiency, low temperature rise, alarm boost, LED lighting, smoke alarm, doorbell, welcome sensor, anti-lost device, smart lock alarm inductor, atomizer, aromatherapy machine, humidifier, etc.
In short, the three-pin inductor is an electronic component widely used in electronic circuits, and plays an important role in various fields.
