What is an autotransformer and its characteristics

Autotransformer refers to a transformer whose primary and secondary windings are on the same winding, and the primary and secondary windings are directly connected in series and self-coupled. According to the structure, it can be subdivided into adjustable pressure type and fixed type. Auto-coupling means electromagnetic coupling. Ordinary transformers transfer energy through the electromagnetic coupling of the primary and secondary coils. There is no direct electrical connection between the primary and secondary sides. The primary and secondary sides of the autotransformer have direct electrical connections. Its low-voltage coils It is part of the high voltage coil. Protective equipment such as autotransformers are also used in protective equipment for communication lines.

Chinese name auto transformer, foreign name auto transformer Features: secondary winding is part of the original winding power phase number single-phase and three-phase cooling methods natural cooling, air-cooled or water-cooled disciplines power and radio communications, etc.

Ⅰ. What is an autotransformer:

The secondary winding of an autotransformer is an integral part of the primary winding. Such a transformer seems to have only one winding, so it is also called a "single winding transformer". The primary and secondary coupled inductors can be decoupled according to the three-terminal coupled inductors connected to the opposite ends in the circuit theory. Applying a voltage on the primary side and the secondary side is short-circuited, or applying a voltage on the secondary side and the primary side is short-circuited, the equivalent leakage reactance reduced to the primary or secondary side of the autotransformer can be obtained. The autotransformer is a special transformer that does not need to be insulated between the primary and secondary, that is, a special transformer that shares a set of coils for the output and input. In other words, a transformer with primary and secondary windings on the same winding.

Ⅱ, the characteristics of autotransformer:

1. Because the calculated capacity of the autotransformer is less than the rated capacity. Therefore, under the same rated capacity, the main size of the autotransformer is smaller, and the effective materials (silicon steel sheets and wires) and structural materials (steel) are reduced accordingly, thereby reducing the cost. The reduction of effective materials reduces copper loss and iron loss correspondingly, so the efficiency of the autotransformer is higher. At the same time, due to the reduction of the main size and quality, a single transformer with a larger capacity can be manufactured under allowable transportation conditions.

2. Since the nominal value of the short-circuit impedance of the autotransformer is smaller than that of the dual-winding transformer, the voltage change rate is smaller, but the short-circuit current is larger.

3. Due to the direct electrical connection between the primary and secondary autotransformers, when the high-voltage side is over-voltage, it will cause serious over-voltage on the low-voltage side. In order to avoid this danger, the primary and secondary windings must be installed with lightning arresters. Don't think that the primary and secondary windings are connected in series. Once the primary and secondary windings are installed, the secondary can be omitted.

4. In general transformers. The on-load voltage regulating device is often connected to the neutral point of the ground, so that the voltage level of the voltage regulating device can be lower than that of the line end voltage regulation. The neutral point voltage regulation side of the autotransformer will bring so-called related voltage regulation problems. Therefore, when the autotransformer is required to adjust the voltage under load, only the end-of-line voltage adjustment method can be used.