Transformer.
A transformer is an electrical device used to change the alternating current voltage, and the basic principle is to use electromagnetic induction. A transformer consists of two coils, i.e., windings, that are connected to each other by a magnetic material, usually an iron core. When an alternating current is added to the input coil, i.e., the primary coil, a varying magnetic field is generated. This magnetic field passes through the core and is induced into the output coil (i.e., the secondary coil), where the voltage is induced. Depending on the turns ratio of the coil, the relationship between the input and output voltages can be determined by the transformer ratio. According to Faraday's law of electromagnetic induction, transformers require alternating currents to pass through when working, because only a changing magnetic field can induce a voltage in the secondary coil. Therefore, the transformer can only change the AC voltage and has no effect on the DC voltage. In short, the transformer realizes the upward and downward conversion of AC voltage through the principle of electromagnetic induction, which is an important equipment commonly used in the power system.
The transformer mainly realizes two types of voltage changes: step-up and step-down.
Boost transformer: A boost transformer raises the voltage of the input coil (primary coil) to a higher output voltage. This is achieved by having fewer turns of the primary coil than the number of turns of the secondary coil. When the input voltage is applied to the primary coil, the voltage induced in the secondary coil is higher than the input voltage, and the voltage is boosted.
Step-down transformer: A step-down transformer reduces the voltage of the input coil (primary coil) to a lower output voltage. This is achieved by having more turns of the primary coil than the number of turns of the secondary coil. When the input voltage is applied to the primary coil, the voltage induced in the secondary coil is lower than the input voltage, and the voltage is reduced.
Whether they are step-up or step-down transformers, they all follow the law of conservation of electrical energy, which states that the output power is equal to the input power. Therefore, the transformer changes the voltage as well as the current. According to the transformer voltage ratio and the law of conservation of electrical energy, the relationship between the input voltage, the output voltage, and the current can be determined. In addition to changing voltage, transformers also have some other important features, such as isolating input and output circuits, reducing line losses, providing convenience for power transmission and distribution, etc. As a result, transformers of various types and sizes are widely used in power systems.
The insulation structure of a transformer is usually composed of the following parts:
Winding insulation: The windings of transformers are made of wires or foils, and in order to ensure insulation between the windings and between the windings and the core, they are usually wrapped with insulating materials. Common insulating materials include paper, insulating varnish, insulating sheets, etc.
Insulating oil: The inside of the transformer is usually filled with insulating oil, which has good insulation properties and heat dissipation properties. Insulating oil mainly plays the role of cooling windings and improving dielectric strength.
Insulating sleeve: An insulating sleeve is usually provided between the winding and the core to isolate the electric field between the winding and the core. Insulating sleeves are generally made of insulating materials, such as silicone rubber.
Insulating strips: Insulating strips are used to isolate windings of different phases and different voltage levels. It is usually made of insulating materials such as cardboard, insulating paint cloth.
Insulating gaskets: Insulating gaskets are used to isolate the electric field between the windings and the housing, usually between the windings of the transformer and the housing.
The insulation structure of the transformer ensures that the transformer can effectively isolate the electric field during operation, prevent the occurrence of accidents such as electric shock and leakage, and improve the dielectric strength and heat dissipation effect, so as to ensure the safe and stable operation of the transformer.