How does an autotransformer work? Want to know more about transformers

An autotransformer is a transformer with only one winding, and when used as a step-down transformer, a part of the line turns are extracted from the winding as a secondary winding; When used as a step-up transformer, the applied voltage is only applied to the turn-part of the winding. Usually belong to the part of the winding that belongs to the primary and secondary at the same time is called the common winding, the rest of the part is called the series winding, the same capacity of the self-coupling transformer compared with the ordinary transformer, not only small size, but also high efficiency, and the larger the transformer capacity, the higher the voltage This advantage is more prominent. Therefore, with the development of the power system, the improvement of the voltage level and the increase of the transmission capacity, the self-lotus transformer has been widely used due to its large capacity, low loss and low cost.

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Compared with ordinary double-winding transformers, autotransformers have the following main characteristics:

1) Since the calculated capacity of the autotransformer is less than the rated capacity, the main size of the autotransformer is smaller under the same rated capacity, 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 leads to a corresponding reduction in copper and iron consumption, so the efficiency of the autotransformer is higher. At the same time, due to the reduction of the main size and mass, it is possible to manufacture a single transformer with a larger capacity under the allowable transportation conditions.

However, these advantages are usually only apparent when there is only k 2 in autotransformers.

2) Because the short-circuit impedance standard value of the autotransformer is smaller than that of the double-winding transformer, the voltage change rate is smaller, but the short-circuit current is larger. Check the Minrong Electric Group, which is also very complete about the principle of the transformer, and the Minrong transformer is also quite good, you can learn about the Minrong Electric Group.

3) Due to the autotransformer.

There is a direct connection between the primary and secondary electricity, and when the high-voltage side is over-voltaged, it will cause serious overvoltage on the low-voltage side. In order to avoid this danger, it is necessary to install a lightning arrester once or twice, do not think.

The primary and secondary windings are connected in series, and can be omitted once and twice.

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 first end of the voltage regulation. The neutral voltage regulation side of the autotransformer will bring about the so-called related voltage regulation problem.

Therefore, when the autotransformer is required to regulate the voltage on load, the line-end voltage regulation mode can only be used.

How it works: Wound two or more coils around a closed core, and when one coil is fed AC power, an alternating current flows through the coil.

This alternating current generates an alternating magnetic field in the core, and the alternating main flux generates its own electromotive force in the primary coil and a mutual induced electromotive force in the other coil.

The primary and secondary side coupled inductors can be decoupled according to the three-terminal coupled inductors connected to the different ends in circuit theory. When a voltage is applied to the primary side and the secondary side is shorted, or a voltage is applied to the secondary side and the primary side is shorted, the equivalent leakage reactance attributed to the primary or secondary side of the autotransformer can be obtained.

The working principle of the autotransformer is that when a coil is connected to the AC power supply (that is, the primary coil), an alternating current flows through the coil, and this alternating current generates an alternating magnetic field in the core, and the alternating main magnetic flux generates its own induced electromotive force in the primary coil, and at the same time, the other coil (that is, the secondary coil) induces mutual inductive electromotive force. By changing the relationship between the ratio of the turns of the primary and secondary coils, the voltage at the end of the primary and secondary coils is changed to realize the voltage conversion.

When an autotransformer is used as a step-down transformer, a part of the line turns are extracted from the winding as a secondary winding; When used as a step-up transformer, the applied voltage is only applied to the turn-part of the winding. Usually the part of the winding that belongs to both the primary and secondary is called the common winding, and the rest of the autotransformer is called the series winding, and the autotransformer with the same capacity is not only small in size compared with the ordinary transformer, but also has high efficiency, and the larger the transformer capacity, the higher the voltage.

This advantage is even more prominent. Therefore, with the development of power system, the improvement of voltage level and the increase of transmission capacity, autotransformers have been widely used due to their large capacity, small loss and low cost.

Electrician knowledge: autotransformer step-down starting circuit, working principle, wiring steps explained one by one.

Principle: After the motor is started, the motor is separated from the autotransformer, so as to move normally under full voltage. This step-down start is divided into two types: manual control and automatic control.

The high-voltage side of the autotransformer is fed into the grid, and the low-voltage side is connected to the motor, and there are several taps with different voltage ratios to choose from.

Ordinary transformers include primary coils and secondary coils. The self-even transformer is not divided into primary secondary coils, and the outermost layer of the self-even transformer coil, that is, the outermost edge of the coil, that is, a wire head of the coil is wound, which is equivalent to the connection of the primary secondary coil. The innermost part of the transformer (where the coil begins to wrap) is a wire end.

On the outer enamelled wire coil, connect one or more heads, and there will be a small voltage output.

Whether it is an ordinary transformer or an autotransformer, it uses the principle of electromagnetic induction.

No matter what form of transformer, it uses the principle of electromagnetic induction to work.

The autotransformer is made according to the self-inductance phenomenon in the electromagnetic induction phenomenon, which mainly regulates the voltage level.

Self-induced electromotive force is an electromotive force generated at both ends of the coil due to a change in the current passing through the coil itself, which causes a change in the magnetic flux passing through the coil. Because the level of the induced electromotive force is directly proportional to the number of turns of the coil, the electromotive force generated by the local windings in the entire coil must be lower than the electromotive force generated by all the windings. If the local winding and all the windings are used as primary and secondary respectively, an autotransformer is constituted.

Similarly, changing the turns ratio of the two parts of the winding also changes the transformer ratio.

The autotransformer has a simple structure and low cost. The auto-transformer and auto-regulator are widely used. However, because the primary and secondary stages of the autotransformer are not isolated in the circuit, the safety performance is not high.

Therefore, the use of autotransformers is prohibited in places where the use of safe voltages is required.

There are two kinds of autotransformers, one is the autotransformer (three-phase) for the decompression start of the power supply motor, and the other is an autotransformer with multiple taps of the winding. The principle is to change the winding tap to obtain a transformer that increases the voltage or decreases the voltage. There is also a continuous toroidal voltage regulator that belongs to this type of transformer.

Hence the name, it is a self-inductive transformer. The specific principle is introduced separately according to the different environment and circuits used. It is recommended that you refer to:

Electrical data health network, 1-to-4 auto-decompression start.

Autotransformers are mainly used for on-load voltage regulation and step-down start-up of large motors, due to.

The primary and secondary windings are directly connected, and the low-voltage output terminal is also easy to cause danger, so the autotransformer cannot be used as a safety transformer.