How Transformers Work？

     A transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the iron core (magnetic core). The main functions are: voltage transformation, current transformation, impedance transformation, isolation, voltage regulation (magnetic saturation transformer), etc. According to the purpose, it can be divided into: power transformers and special transformers (electric furnace transformers, rectifier transformers, power frequency test transformers, voltage regulators, mining transformers, audio transformers, intermediate frequency transformers, high frequency transformers, impact transformers, instrument transformers, electronic transformers , reactors, transformers, etc.). Circuit symbols often use T as the beginning of the number. Example: T01, T201, etc.

       In 1881, Lucien Gaulard and John Dixon Gibbs demonstrated a device called a "secondary hand generator" in London, and then sold the technology to Westinghouse in the United States. This may be the first practical power transformer, but Not the first transformer.

       In 1884, Lussen Golar and John Dixon Gibbs demonstrated their equipment in the Italian city of Turin, which used electric lighting. Early transformers used straight cores, which were later replaced by more efficient toroidal cores.

       Westinghouse engineer William Stanley built the first practical transformer in 1885, after buying transformers from George Westinghouse, Luthan Golar, and John Dixon Gibbs. transformer. Later, the iron core of the transformer was made by stacking E-type iron sheets, and it began to be used commercially in 1886.

       The principle of transformer transformation was first discovered by Faraday, but it was not practically applied until the 1880s. The ability to use transformers for alternating current is one of its advantages in a race where power plants should output both direct current and alternating current. Transformers can convert electrical energy into high voltage and low current form, and then convert it back, thus greatly reducing the loss of electrical energy in the transmission process, making the economical transmission distance of electrical energy to reach a longer distance. That way, power plants can be built far away from electricity use. Most of the world's electricity goes through a series of transformations before finally reaching the consumer.

       The working principle of the transformer: The transformer uses the principle of electromagnetic induction, and the amount of electric energy transmitted by an electrical appliance that transmits electrical energy or transmits signals from one circuit to another circuit is determined by the power of the electrical appliance.

       The structure of the transformer consists of an iron core (or magnetic core) and a coil. The coil has two or more windings. The winding connected to the power supply is called the primary coil, and the rest of the windings are called secondary coils. It can transform AC voltage, current and impedance. The simplest iron core transformer consists of an iron core made of soft magnetic material and two coils with different turns on the iron core, as shown in the figure.

      The role of the iron core is to strengthen the magnetic coupling between the two coils. In order to reduce the eddy current and hysteresis loss in the iron, the iron core is laminated by lacquered silicon steel sheets; there is no electrical connection between the two coils, and the coils are wound by insulated copper wire (or aluminum wire). One coil connected to the AC power supply is called the primary coil (or primary coil), and the other coil connected to the electrical appliance is called the secondary coil (or secondary coil). The actual transformer is very complicated, and there are inevitably copper loss (coil resistance heating), iron loss (iron core heating) and magnetic leakage (magnetic induction line closed by air), etc. In order to simplify the discussion, only the ideal transformer is introduced here. The conditions for the establishment of an ideal transformer are: ignoring the leakage flux, ignoring the resistance of the primary and secondary coils, ignoring the loss of the iron core, and ignoring the no-load current (the current in the primary coil with an open secondary coil). For example, when the power transformer is running at full load (the secondary coil outputs rated power), it is close to the ideal transformer condition.

       Transformers are static electrical appliances made using the principle of electromagnetic induction. When the primary coil of the transformer is connected to the AC power supply, an alternating magnetic flux is generated in the iron core, and the alternating magnetic flux is represented by φ. The φ in the primary and secondary coils is the same, and φ is also a simple harmonic function, and the table is φ=φmsinωt. According to Faraday's law of electromagnetic induction, the induced electromotive force in the primary and secondary coils is e₁=-N₁dφ/dt, e₂=-N₂dφ/dt. In the formula, N₁ and N₂ are the turns of the primary and secondary coils. It can be seen from the figure that U₁=-e₁, U₂=e₂ (the physical quantity of the primary coil is represented by subscript 1, and the physical quantity of the secondary coil is represented by subscript 2), and its complex effective value is U₁=-E₁=jN₁ωΦ, U₂=E₂=- jN₂ωΦ, Let k=N₁/N₂, which is called the transformation ratio of the transformer. U₁/U₂=-N₁/N₂=-k can be obtained from the above formula, that is, the ratio of the rms voltage of the primary and secondary coils of the transformer is equal to its turns ratio and the phase difference between the primary and secondary coil voltages is π.

       Which leads to:

       U₁/U₂=N₁/N₂

       In the case that the no-load current can be ignored, there is I₁/I₂=-N₂/N₁, that is, the RMS value of the primary and secondary coil currents is inversely proportional to the number of turns, and the phase difference is π.

       thus obtainable

       I₁/ I₂=N₂/N₁

       The powers of the primary and secondary coils of an ideal transformer are equal to P₁=P₂. It shows that the ideal transformer itself has no power loss. The actual transformer always has losses, and its efficiency is η=P₂/P₁. The efficiency of power transformers is very high, reaching more than 90%.

       The Satons transformer mainly uses the principle of electromagnetic induction to work. Specifically: when the AC voltage U₁ is applied to the primary side of the transformer, and the current flowing through the primary winding is I₁, the current will generate an alternating magnetic flux in the iron core, so that the primary winding and the secondary winding are electromagnetically connected. According to the principle of electromagnetic induction When the alternating magnetic flux passes through these two windings, an electromotive force will be induced, and its magnitude is proportional to the number of winding turns and the maximum value of the main magnetic flux. The side with more winding turns has a higher voltage, and the side with fewer winding turns has a higher voltage. When the voltage is low, when the secondary side of the transformer is open, that is, when the transformer is no-load, the voltage of the primary and secondary terminals is proportional to the number of turns of the primary and secondary windings, that is, U₁/U₂=N₁/N₂, but the primary and secondary frequencies remain the same, so realize the change of voltage.