What causes voltage to be induced in a transformer？

The working principle of the transformer is a static electrical device that exchanges AC voltage or current between two or more windings at the same frequency by means of electromagnetic induction. That is, its working principle is "electricity generates magnetism, magnetism generates electricity".

The working principle of the transformer is electromagnetic induction, but strictly speaking, it is because of the mutual induction phenomenon. The following is an explanation of the induction law and the mutual induction phenomenon:

Principle of electromagnetic induction: When the magnetic flux associated with the coil changes (or we can understand that the magnetic flux passing through or through the coil changes), the coil will induce an electromotive force (electromotive force is a physical quantity used to characterize the power supply, commonly known as current), and when the magnetic flux passing through the coil keeps changing continuously, this induced electromotive force (induced current) will be generated continuously accordingly. This is the most intuitive explanation of "electromagnetism".

Specifically, according to Faraday's electromagnetic induction principle, the amplitude of the induced electromotive force (induced current) is proportional to the rate of change of the magnetic flux passing through the coil. We can explain this statement more intuitively in a mathematical way, , where E is the induced electromotive force, N is the number of turns of the coil, and is the rate of change of the magnetic flux.

Let's look at mutual inductance: the changing alternating current in the primary coil generates a changing magnetic field, and the changing magnetic field passes through the secondary coil, which induces an electromotive force in the secondary coil, that is, an induced current: EMF. Mutual inductance is a direct result of Faraday's law.

Transformers are the best example of mutual inductance, and we define it as follows: when a changing current in one coil induces an electromotive force (current) in another adjacent coil, the phenomenon that occurs is called mutual inductance (which is what we commonly call "electricity generates magnetism, magnetism generates electricity").

In detail, according to Lenz's law, the current generated by the mutual inductance between two coils is affected by the mutual inductance coefficient (the mutual inductance coefficient (M) quantifies the degree of mutual inductance between the two coils), which is measured in Henry (H) according to electronic data. The mutual inductance of the two coils is the same. .

According to the function, transformers can be divided into step-up transformers and step-down transformers.The following are the main functions of the two types of transformers.

Long-distance power transmission: When we want to carry out long-distance power transmission, low-voltage current is far inferior to high-voltage current in terms of cost-effectiveness and work efficiency. Therefore, we generally do not use low-voltage current for long-distance power transmission in the power system, because low-voltage current is not only slow in the circuit, but also due to the existence of resistance in the circuit, the heat loss per unit area is also greater.

In order to avoid the above situation, we usually use power transformers (step-up transformers) to increase the voltage of the sender and reduce the current passing through the transmission line per unit time, thereby reducing the energy loss caused by resistance during transmission.

By using step-up transformers (click to learn about step-up transformers), we can efficiently transmit electricity from power plants to power consumption areas far away from power sources. (Regarding the issue of enameled copper wire and enameled aluminum wire, Yawei transformers are also trustworthy.)

Adapt to load requirements: Different electrical equipment and systems have different voltage requirements. Power transformers can convert high-voltage electrical energy into low-voltage electrical energy (step-down transformers) suitable for specific equipment or systems to ensure the normal operation of the equipment. For example, low-voltage equipment and high-voltage poles used in daily life are good reference objects: high-voltage poles are part of the power system. Due to transmission requirements, their voltage is usually higher than the voltage of our daily electrical equipment, but our daily electrical equipment does not need such a high voltage, so the current needs to be stepped down.

The factors affecting transformer current are mainly copper loss and core loss. And the basic working principle determines that the transformer will not produce much loss under the law of conservation of energy.And now, Modern transformers can typically achieve efficiencies between 95% and 99%, depending on design, materials, and operating conditions.For high-power transformers, efficiencies are typically between 98% and 99% when well designed and properly loaded.For small and medium-power transformers, efficiencies may be slightly lower, typically between 95% and 98%. For older or lower-quality transformers, efficiencies may be less than 95%.

Use highly conductive materials: Choose high-quality copper or aluminum as winding materials to reduce resistance. Why does reducing resistance reduce losses? Because resistance acts as an obstacle in power transmission, unnecessary heat loss will be generated due to the existence of resistance when current passes through, so reducing resistance will reduce energy loss and achieve energy saving.

Optimize winding design: Use thicker coils to reduce the resistance of the windings, and design a reasonable winding layout to reduce the current path. Copper loss is the heat generated by the resistance of current passing through the conductor. When the coil is thicker, the cross-sectional area of the conductor increases and the resistance decreases accordingly. This means that when the same current pass by, the thicker coil will produce less heat loss. At the same time, thick coils can make the current more evenly distributed in the conductor that can reduce local heating caused by excessive current density. This helps to reduce overall heat loss. In addition, thicker coils can dissipate heat more effectively, reducing additional losses caused by increased temperature. Good heat dissipation performance helps to keep the conductor working at a lower temperature, thereby improving efficiency. The last point is to reduce the skin effect: under high-frequency operation, the current tends to concentrate on the surface of the conductor, which is called the skin effect. Thicker coils provide a larger surface area, reducing the impact of skin effect on current distribution and thus reducing losses.

Use high-performance core materials

Low-loss silicon steel sheets:We can choose low-loss silicon steel sheets or ferrite materials that have high magnetic permeability and low hysteresis losses. (Hysteresis loss: Energy is consumed when the magnetic material is repeatedly magnetized and demagnetized in a magnetic field)

Improving alloy composition:Use alloyed core materials to reduce eddy current losses. (When a changing magnetic field generates eddy currents in the core, these eddy currents cause energy loss. Using materials such as silicon steel sheets can reduce eddy current losses.)

Use laminated cores

Laminated design: Divide the core material into multiple thin sheets, insulate each other, reduce the formation of eddy currents, and thus reduce losses.

Optimize the core shape

Toroidal core: Use a toroidal or closed core design to improve the coupling efficiency of the magnetic flux and reduce leakage losses. (Leakage loss: Energy loss caused by incomplete coupling of magnetic field. This part of energy is not transferred to the secondary winding.)

Increase the operating frequency

In some cases, increasing the operating frequency of the transformer can reduce iron loss, because at high frequency, the area of ​​the hysteresis loop becomes smaller and the loss will be reduced accordingly.

Reduce the operating temperature

Through an effective cooling system, keep the operating temperature of the transformer within a suitable range to reduce the loss caused by temperature increase.

Optimize the flux density

Reasonable design: According to the application of the transformer, the                                                                                                               flux density of the core is reasonably designed to avoid additional losses                                                                                                               caused by excessive flux density.

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