A power transformer converts an AC voltage of a certain voltage level into another or several levels of AC voltage with the same frequency. When the primary winding is supplied with alternating current, alternating magnetic flux is generated, and the alternating magnetic flux induces an alternating electromotive force in the secondary winding through the magnetic conduction of the iron core. The level of the secondary induced electromotive force is related to the number of turns of the primary and secondary windings, that is, the voltage is proportional to the number of turns. The main function of the power transformer is to transmit electric energy, therefore, the rated capacity is its main parameter. Rated capacity is a customary value for expressing power, which represents the size of transmitted electric energy, expressed in kVA or MVA.
Transformers can be divided into step-up transformers and step-down transformers according to their functions; according to the number of phases: single-phase transformers and three-phase transformers; according to the number of windings: double-winding transformers (one voltage is changed to another voltage is Double-winding transformer), three-winding transformer (three-winding transformer with one voltage changed to two voltages), multi-winding transformer; according to the voltage regulation method, it can be divided into two types: non-excitation voltage regulating transformer and on-load voltage regulating transformer.
The distribution transformer in the power system is a step-down transformer, which is generally a double-winding, oil-immersed self-cooling structure, and mostly adopts a non-excitation voltage regulation method. It is usually installed on a tower or in a power distribution station, and can generally reduce the voltage from 10kV (20kV) to about 220/380V for input to users. Dry-type transformers and oil-immersed transformers cooled with oil are mainly used in power distribution equipment. (The power distribution station (public distribution station) is mainly a dry-type transformer, and the hanger on the tower is an oil-immersed transformer).
The basic structure of the transformer consists of: iron core, winding, bushing, oil tank and transformer pump, oil conservator and respirator, off-load tap changer and other accessories (①Elevating ring, located on the box cover, used to lift the transformer body ( Core). Lifting rings are not allowed to lift the entire transformer, so as to avoid deformation of the box cover and oil leakage along the side of the box. ②Hook, located under the side of the box. Used to lift the entire transformer. ③Refueling plug, located on the box cover, It is used for refueling of the transformer.④ Thermometer seat, located on the box cover, used to measure the oil temperature of the upper layer of the transformer).