The description of auto transformer
Auto-coupling means electromagnetic coupling. The ordinary transformer transfers energy through the electromagnetic coupling of the primary and secondary coils. The primary and secondary sides have no direct electrical connection. The primary and secondary sides of the auto transformer have direct electrical connection. It is part of the high-voltage coil. Auto transformer refers to the transformer whose winding is the primary and secondary on the same winding. According to the structure, it can be subdivided into adjustable pressure type and fixed type.
The features of auto transformer
(1) Because the calculated capacity of the auto transformer is less than the rated capacity. Therefore, under the same rated capacity, the main size of the auto transformer is small, and the effective materials (silicon steel sheets and wires) and structural materials (steel) are reduced accordingly, thereby reducing costs. The reduction in effective materials reduces the copper and iron losses accordingly, so the efficiency of the auto transformer is higher. At the same time, due to the reduction of the main size and the reduction of quality, a single transformer with a larger capacity can be manufactured under the allowable transportation conditions.
⑵ Since the unit value of the short-circuit impedance of the auto transformer is smaller than that of the dual-winding transformer, the voltage change rate is small, but the short-circuit current is large.
(3) Due to the direct electrical connection between the primary and secondary of the auto transformer, when the high voltage side is overvoltage, it will cause a serious overvoltage on the low voltage side. In order to avoid this danger, lightning arresters must be installed once or twice.
⑷In general transformers. The on-load voltage regulating device is often connected to the grounded neutral point, so that the voltage level of the voltage regulating device can be lower than that when the line terminal regulates voltage. The neutral voltage regulation side of the auto transformer will bring about the so-called related voltage regulation problem. Therefore, when the on-load voltage regulation of the auto transformer is required, the terminal voltage regulation method can only be used.
The working principle of auto transformer
1. Auto transformer is a special transformer that shares a set of coils for output and input. Different taps are used to boost and step down. The voltage of some taps that are less than the common coil is reduced. The voltage of some taps that are more than the common coil is increased. high.
⒉In fact, the principle is the same as the ordinary transformer, except that his primary coil is its secondary coil. In general transformers, the primary coil on the left generates electromagnetic voltage through the secondary coil on the right, and the auto transformer influences itself.
⒊The auto transformer is a transformer with only one winding. When used as a step-down transformer, a part of the windings are drawn from the windings as a secondary winding; when used as a step-up transformer, the applied voltage is only applied to part of the windings. on. Usually the part of the windings that belong to both the primary and the secondary is called the common winding, and the rest of the auto transformer is called the series winding. Compared with the ordinary transformer, the auto transformer of the same capacity is not only small in size, but also high in efficiency and the transformer The larger the capacity, the higher the voltage. This advantage becomes even more prominent. Therefore, with the development of the power system, the increase in voltage level and the increase in transmission capacity, the auto transformer has been widely used because of its large capacity, small loss, and low cost.
The advantages of auto transformer
1. Less material consumption and low cost. Because the amount of silicon steel sheet and copper wire used in the transformer is related to the rated inductive potential and rated current of the winding, that is, the capacity of the winding, the capacity of the auto transformer winding is reduced, the materials consumed are also reduced, and the cost is also low.
2. Less loss and higher benefit. Due to the reduction in the amount of copper wire and silicon steel sheet, at the same current density and magnetic flux density, the copper loss and iron loss of the auto transformer are reduced compared with the double winding transformer, so the benefit is higher.
3. Easy to transport and install. Because it is lighter in weight, smaller in size and smaller in area than a dual-winding transformer of the same capacity.
4. Increased the limit manufacturing capacity of the transformer. The ultimate manufacturing capacity of the transformer is generally limited by the transportation conditions. Under the same transportation conditions, the auto transformer capacity can be larger than that of the dual-winding transformer under the same transportation conditions.