The birth of inductance
Time：2021.10.14
View：
It is difficult to trace the birth history of inductors. Even after consulting various experts such as Gu Ge, the answers are still vague. Who is the father of Inductor? Some historical data pointed out that in August 1830, Henry discovered the phenomenon of electromagnetic induction, one year earlier than Faraday. In 1832, Henry published the paper "Electrical Self-inductance in a Long Spiral Line", announcing the discovery of the phenomenon of electrical self-inductance. In addition, Henry invented relays, non-inductive windings, improved an original transformer, and invented an original electric motor like a seesaw. To commemorate this world-recognized electrician, the international unit of inductance is named after Henry. Therefore, it makes sense that your name is Henry.
What you see here is a battery, a light bulb, a coil around the (yellow) iron block, and a switch. The coil is the inductor. If you understand the working principle of an electromagnet, you will know that an inductor is an electromagnet.
Chip inductance
Plug-in inductor Toroidal inductor
The working principle of the inductor: a simple coil, a magical magnetic field.
The bulb is a resistor, and the resistance of the wire in the coil is much lower (it is just a wire), so when you turn on the switch, you will see the bulb emit dim light. Most of the current will pass through the loop via a low resistance path. What actually happens is that when you close the switch, the bulb is bright at first and then dim. When you turn on the switch, the light bulb becomes very bright and then quickly goes out.
It is the inductor that causes this strange phenomenon. When current starts to flow in the coil for the first time, the coil forms a magnetic field. In the process of forming a magnetic field, the coil prevents the flow of current. Once the magnetic field is formed, current can pass through the wire normally. When the switch is turned on, the magnetic field around the coil causes current to flow in the coil until the magnetic field disappears. This current can keep the light bulb illuminated for a period of time even when the switch is turned on. In other words, an inductor can store energy in its magnetic field and generally prevents any changes in the magnitude of the current flowing through it.
An intuitive way to understand the working principle of an inductor is to imagine a narrow water pipe with water flowing through it, and at the same time a heavy water wheel with paddles immersed in the water pipe. Imagine that the water in the pipe does not flow at first. Now you try to start to make the water flow. The water wheel will stop the flow of water until it rotates with the speed of the water flow. If you try to stop the flow of water in the water pipe, the rotating water wheel will keep the water moving until the speed of the water wheel slows down to the speed of the water flow. The working principle of the inductor is the same, that is, electrons flow in the wire-the inductor prevents the electron flow from changing.
Inductor's last name: Henry
The standard unit of inductance is Henry. The equation for calculating the Henry's number of inductors is as follows:
H=(4 * 3.14159 * number of turns * number of turns * coil area * mu)/(coil length * 10,000,000)
The unit of the area and length of the coil is meter. The symbol mu is used to indicate the magnetic permeability of the core. The permeability of air is 1, while the permeability of steel may be 2,000.
Ms. Inductor's various dresses
Classified by structure
Inductors can be divided into wire-wound inductors and non-wire-wound inductors (multilayer chip, printed inductors, etc.) according to their structure, and can also be divided into fixed inductors and adjustable inductors.
According to the mounting method: there are chip inductors and plug-in inductors. At the same time, the inductors with external shielding become shielded inductors, and those with exposed coils are generally called unshielded inductors.
Chip inductance
Plug-in inductor Toroidal inductor
Color ring inductance
Fixed inductors are divided into hollow electronic watch inductors, magnetic core inductors, iron core inductors, etc. According to their structure and shape and pin mode, they can also be divided into vertical co-directional pin inductors and horizontal axial pin inductors. Inductors, large and medium-sized inductors, small and exquisite inductors and chip inductors, etc.
Adjustable inductors are divided into magnetic core adjustable inductors, copper core adjustable inductors, sliding contact adjustable inductors, series mutual inductance adjustable inductors and multi-tap adjustable inductors.
Classified by working frequency
Inductance can be divided into high frequency inductors, intermediate frequency inductors and low frequency inductors according to the operating frequency.
Air core inductors, magnetic core inductors and copper core inductors are generally medium frequency or high frequency inductors, while iron core inductors are mostly low frequency inductors.
Classified by purpose
Inductors can be divided into oscillation inductance, correction inductance, kinescope deflection inductance, blocking inductance, filter inductance, isolation inductance, and compensation inductance according to their purpose. At the same time, Gybis power inductors are used in situations such as large currents.
Oscillation inductors are divided into TV line oscillation coils, east-west pincushion correction coils and so on.
CRT deflection inductors are divided into line deflection coils and field deflection coils.
choke inductors (also called choke coils) are divided into high-frequency choke coils, low-frequency choke coils, choke coils for electronic ballasts, TV line frequency choke coils, and TV airport frequency choke coils.
Filter inductors are divided into power supply (power frequency) filter inductors and high-frequency filter inductors.
Ms. The power of inductance: "Capacity" is great
Basic functions: filtering, oscillation, delay, notch, etc.
Vivid saying: "pass DC, block AC"
Detailed explanation: In electronic circuits, the inductance coil acts on the AC current limitation. It can form a high-pass or low-pass filter, phase-shifting circuit and resonant circuit with resistors or capacitors; transformers can perform AC coupling, transformation, and transformation. Flow and impedance transformation, etc.
Among them, L is the inductance, and I is the current flowing through the inductance. It can be seen that the greater the coil inductance and the greater the flow, the more electric energy stored.
The most common role of inductors in circuits is to form an LC filter circuit together with capacitors. We already know that capacitors have the ability to "block DC and pass AC", while inductors have the function of "pass DC and block AC". If the DC power with many interference signals is passed through the LC filter circuit, the AC interference signal will be consumed by the capacitor as heat; when the pure DC current passes through the inductor, the AC interference signal in it will also become magnetic induction And heat energy, the higher frequency is most likely to be impedance by the inductance, which can suppress the higher frequency interference signal.
The noble status of inductors: applications in analog circuits and signal processing
The combination of inductance elements and capacitive elements and other devices can form a tuned circuit that can amplify or filter certain signal frequencies.
Large inductances can be used in power supply valves (chokes), and they were often used in conjunction with filters to remove the redundant and fluctuating components of the DC output.
Magnetic beads or surrounding cables can generate small inductance to prevent radio frequency interference in the transmission line.
Small capacitance/inductance can also be combined to produce a tuning circuit for radio transmission and reception.
The coupling magnetic flux between two or more inductance elements can form a transformer, which is the basic component of a power supply system. The efficiency of the transformer decreases as the frequency increases, but the volume of the high-frequency transformer also becomes very small. This is why some aircraft use 400 Hz alternating current instead of the usual 50 or 60 Hz. Small transformers save a lot of money. Load.
In a switching power supply, inductive components are used as energy storage components. The inductive element stores energy with a specific part of the switching frequency of the regulator, and releases energy in the second half of the cycle. The energy conversion ratio determines the input-to-output voltage ratio. This XL is used to supplement active semiconductor devices and can be used to precisely control the voltage.
Inductive components are also used in power transmission systems to reduce system voltage or limit fault currents. These are usually used in reactors. Compared with other components, the inductance element is larger and heavier, so its application is reduced in modern equipment; the solid-state switching power supply removes the large transformer, the circuit is converted to use small inductance elements, and the large value is replaced by a gyrator. Circuit simulation.
