Characteristics and Differences Between Double Winding Transformer and Autotransformer

The basic working principle of the transformer is electrical equipment made by using the principle of electromagnetic induction. To put it simply: electricity generates magnetism, and alternating current is applied to the primary side to generate a changing magnetic field in the iron core chamber. The transformer can only input AC voltage. The AC voltage is input from both ends of the primary winding of the transformer. Then it is output from the secondary winding.

Ⅰ. What is a double winding transformer?

The so-called double winding transformer means only two windings in the transformer. There are two windings (two coils) on a phase iron core, one is the primary winding, and the other is the secondary winding. The double winding transformer is a commonly used transformer product. The winding process of the transformer will have different requirements according to different usage occasions (different purposes). Its main functions are voltage transformation, impedance transformation, isolation, voltage stabilization, etc.

Ⅱ. The characteristics of double winding transformers

The double winding transformer is composed of two windings wound on the same iron core, connected by alternating magnetic flux. The voltage with more turns is higher, while the voltage with fewer turns is lower. Therefore it can transform one level of voltage into another level voltage with the same frequency.

Ⅲ. The difference between a double winding transformer and an autotransformer

The primary and secondary windings of the double winding transformer are separately wound. Although each phase is installed on the same iron core, they are insulated from each other. There is only a magnetic coupling between the primary and secondary winding with no electrical connection.

The autotransformer actually has only one winding as the secondary winding connection is tapped from the primary winding. Therefore, there is also a direct electrical connection in addition to the magnetic connection between the primary winding and the secondary winding.

When a double winding transformer transmits electric power, it is transmitted by the electromagnetic induction between the two windings. When autotransformer transmits electric power, part of which is transmitted by electromagnetic induction, and the other part is directly transmitted through circuit connection.

Therefore, when the capacity of the transformer is the same, the winding of the autotransformer will be smaller than that of the double winding transformer. At the same time, the number of silicon steel sheets and wires used in the autotransformer is also reduced with the reduction of the transformation ratio so that the copper and iron losses are also reduced. And the excitation current of the autotransformer is also smaller than that of the double winding transformer. However, since the circuits of the autotransformer's primary and secondary windings are directly connected, an electrical fault on the high-voltage side will affect the low-voltage side. Therefore, appropriate protective measures must be taken.