In an autotransformer, the common portion of the single winding acts as part of both the “primary” and “secondary” windings. The remaining. Electrical Tutorial about the Autotransformer and the Variable Auto The main advantage of this type of transformer design is that it can be made a lot cheaper for the same VA rating, but the biggest disadvantage of an autotransformer is that it. An autotransformer is an electrical transformer with only one winding. The “auto” ( Greek for and cheaper than typical dual-winding transformers, but the disadvantage of not providing electrical isolation between primary and secondary circuits. Other advantages of autotransformers include lower leakage reactance, lower.

Author: Tulkree Akira
Country: Dominican Republic
Language: English (Spanish)
Genre: History
Published (Last): 10 October 2007
Pages: 120
PDF File Size: 5.64 Mb
ePub File Size: 7.30 Mb
ISBN: 610-9-86349-959-4
Downloads: 72618
Price: Free* [*Free Regsitration Required]
Uploader: Akira

In a step-up transformer, conversely, the load is attached across the full winding while the source is connected to a tap across a portion of the winding. No comparable publications seem to exist for American railways, probably due to the paucity of electrified installations there.

The primary and secondary currents are in opposition and the total current flowing through the coils in common is equal to the difference of the current of the low voltage winding and the high disadvantaged winding.

Autotransformer – Wikipedia

A failure of the isolation of the windings of an autotransformer can result in full input voltage applied to the output. Depending on the application, that portion of the winding used solely in the higher-voltage lower current portion may be wound with wire of a smaller gauge, though the entire winding is directly connected.

Disaxvantages autotransformer has a single winding on an iron core. An autotransformer is an electrical transformer with only one winding.

In an autotransformer, the total power transmitted from the primary to the secondary does not actually pass through the whole winding. In railway applications, it is common to power the trains at 25 kV AC. The ” auto ” Greek for “self” prefix refers to the single coil acting alone, not to any kind of automatic mechanism.

Like multiple-winding transformers, autotransformers use time-varying magnetic fields to transfer power. It has a single coil wound on the core, but has four terminals, two for each circuit, and therefore has points in common with the transformer.

Auto-Transformers Advantages Disadvantages

These are important safety considerations when deciding to use an autotransformer in a given application. On load condition, a part of the load current is obtained directly from the supply and the remaining part is obtained by transformer action. For connections between the two systems at very high voltage, where the power is to be transmitted in the order of GVA Giga Volt-amperesthe use of auto transformer make it possible for high power equipment and can be easily transportable.


By using this site, you agree to the Terms of Use and Privacy Policy. It consists of a winding of ends A and D, which has been made a derivation in the intermediate point B.

Therefore, the resulting current flowing through section BC is I 2 — I 1. On long rural power distribution lines, special autotransformers with automatic tap-changing equipment are inserted as voltage regulatorsso that customers at the far end of the line receive the same average voltage as those closer to the source.

The construction of Auto transformer is shown in the figure below. The variable ratio of the autotransformer compensates for the voltage drop along the line. If one of the center-taps is used for the ground, then the autotransformer can be used as a balun to convert a balanced line connected to the two end taps to an unbalanced line the side with the ground.

A large part is merely transferred electrically by conduction. Auto-transformers in comparison with the double winding transformers are generally advantageous of the voltage ratio is favorable from the point of view of the equivalent size. The apparent power transformed by induction is. Neglecting voltage drops in the windings. The voltage of the primary network, to which the autotransformer will be connected, is V1, applied to points A and D. Auto-transformers in comparison with the double winding transformers are generally advantageous of the voltage ratio is favorable from the point of view of the equivalent size The reduction in the equivalent power in relation to the throughput, reduction in the weight and size, reduction in the no load iron losses and on load losses cooper lossesthe reduction in the no load current and the short circuit impedance If P is the power of the transformer, linear dimensions of the auto transformer vary as P 0.

This page was last edited on 19 Decemberat If the neutral point is not solidly earthed, the lower voltage side can be subjected to high potential in the event of earth fault on high voltage side. There are also autotransformers in which the secondary intake is achieved through a sliding brush, allowing a continuous range of secondary voltages ranging from zero to the voltage of the source.

The advantages and disadvantages of autotransformers will be explained below. At full or rated load, the primary and secondary terminal currents are.


A large three-phase autotransformer may have a “buried” delta winding, not connected to the outside of the tank, to absorb some harmonic currents. In an autotransformer part of the current flows directly from the input to the output, and only part is transferred inductively, allowing a smaller, lighter, cheaper core to be used as well as requiring only a single winding.

In a step-down transformer the source is usually connected across the entire winding while the load is connected by a tap across only a portion of the winding. Note that this transformer, whose rating as an ordinary two-winding transformer is only 10 kVA, is capable of handling 50 kVA as an autotransformer.

Another application is a lighting dimmer that doesn’t produce the EMI typical of most thyristor dimmers. The output voltage adjustment can be manual or automatic.

Power transformers in India Wire harness manufacturer in India. From Wikipedia, the annd encyclopedia. Practical applications of autotransformers include: This will not be possible with normal transformers Auto-transformer Disadvantages: Figure 1 shows the schematic representation of buck connection while figure 2 shows the boost connection. Therefore, the kVA rating of the autotransformer is.

Electrical Machines – I. Electrical Transformers and Power Equipment. In practice, losses mean that both standard transformers and autotransformers are not perfectly reversible; one designed for stepping down a voltage will deliver slightly less voltage than required if avvantages is used to step up.

Autotransformer Advantages and Disadvantages – LORECENTRAL

There are various advantages of the auto transformer, but then also one major disadvantage, why auto transformer is not widely used, is that. Other advantages of autotransformers include lower leakage reactance, lower losses, lower excitation current, and increased VA rating for a given size and mass. Different taps on the winding correspond to different disadvangages, measured from the common end.

Because it requires both fewer windings and a smaller core, an autotransformer for power applications is typically lighter and less costly than a two-winding transformer, up to a voltage ratio of about 3: Please disable your adblocking software or whitelist our website. Auto Transformer also recognized as an auto step down transformer which is similar to any regular transformer but the only difference is that it shares only one winding for transmitting the power.

This article was written by admin