What are the main parameters of the transformer?

　　There are corresponding technical requirements for different types of transformers, which can be expressed by corresponding technical parameters. For example, the main technical parameters of power transformers are: rated power, rated voltage and voltage ratio, rated frequency, operating temperature class, temperature rise, voltage regulation rate, insulation performance and moisture-proof performance. For general low-frequency transformers, the main technical parameters are: Transformer ratio, frequency characteristics, nonlinear distortion, magnetic and electrostatic shielding, efficiency, etc.

　　The main parameters of the transformer are voltage ratio, frequency characteristics, rated power and efficiency.

　　(1) Voltage ratio n

　　The relationship between the voltage ratio n of the transformer and the number of turns and voltage of the primary and secondary windings is as follows: n=V1/V2=N1/N2 where N1 is the primary (primary) winding of the transformer, and N2 is the secondary (secondary) winding winding, V1 is the voltage across the primary winding, and V2 is the voltage across the secondary winding. The voltage ratio n of the step-up transformer is less than 1, the voltage ratio n of the step-down transformer is greater than 1, and the voltage ratio of the isolation transformer is equal to 1.

　　(2) Rated power P This parameter is generally used for power transformers. It refers to the output power when the power transformer can work for a long time without exceeding the limited temperature under the specified operating frequency and voltage. The rated power of the transformer is related to the cross-sectional area of ​​the core and the diameter of the enameled wire. The iron core of the transformer has a large cross-sectional area and a thick enameled wire diameter, and its output power is also large.

　　(3) Frequency characteristic Frequency characteristic means that the transformer has a certain working frequency range, and transformers with different working frequency ranges generally cannot be used interchangeably. Because the transformer works outside its frequency range, the temperature will rise during operation or it will not work normally.

　　(4) Efficiency Efficiency refers to the ratio of transformer output power to input power at rated load. This value is proportional to the output power of the transformer, that is, the greater the output power of the transformer, the higher the efficiency; the smaller the output power of the transformer, the lower the efficiency. The efficiency value of the transformer is generally between 60% and 100%.

　　At rated power, the ratio of the output power of the transformer to the input power is called the efficiency of the transformer, that is,

　　η= x100%

　　where η is the efficiency of the transformer; P1 is the input power and P2 is the output power.

　　When the output power P2 of the transformer is equal to the input power P1, the efficiency η is equal to 100%, and the transformer will not produce any loss. But in fact there is no such transformer. When a transformer transmits electrical energy, losses are always generated, which mainly include copper loss and iron loss.

　　Copper loss refers to the loss caused by the resistance of the transformer coil. When the current passes through the coil resistance to generate heat, a part of the electrical energy is converted into heat energy and lost. Since the coil is generally wound with insulated copper wire, it is called copper loss.

　　The iron loss of the transformer includes two aspects. One is the hysteresis loss. When the AC current passes through the transformer, the direction and size of the magnetic field lines passing through the silicon steel sheet of the transformer change accordingly, causing the molecules inside the silicon steel sheet to rub against each other and release heat energy, thus losing a part of the electrical energy, which is the hysteresis loss. . The other is eddy current losses, when the transformer is operating. There are magnetic lines of force passing through the iron core, and an induced current will be generated on a plane perpendicular to the magnetic lines of force. Since this current forms a closed loop to form a circulating current and is vortex-like, it is called an eddy current. The existence of eddy current makes the iron core heat up and consumes energy, and this loss is called eddy current loss.

　　The efficiency of the transformer is closely related to the power level of the transformer. Generally, the greater the power, the smaller the loss and output power, and the higher the efficiency. Conversely, the lower the power, the lower the efficiency.