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.

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Ordinary Two Winding Transformer. Some of the disadvantages of an autotransformer autotransformef In an ordinary transformer, the primary and the secondary windings are electrically insulated from each other but connected magnetically as shown in the figure below and in auto transformer the primary and the secondary windings are connected magnetically as well as electrically.

At full or rated load, the primary and secondary terminal currents are.

When a voltage V 1 is applied to the primary of the autotransformer, the induced voltages are related by. Also, a break in the part of the winding that is used as both primary and secondary will result in the transformer acting as an inductor in series with the load which under light load conditions may result in near full input voltage being applied to the output. 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 it is used to step up.

No comparable publications seem to exist for American railways, probably due to the paucity of electrified installations there. In audio applications, tapped autotransformers are used to adapt speakers to constant-voltage audio distribution systems, and for impedance matching such as between a low-impedance microphone and a high-impedance amplifier input.

Advantages and disadvantages of the autotransformer

Now, the ratio autotransformre the weight of the copper in an auto transformer to the weight of copper in an ordinary transformer is given as. However, the apparent power in the transformer windings is. A large part is merely transferred electrically by conduction. If the same duty is performed with an ordinary two winding transformer shown above in the figure A.


Other advantages of an autotransformer over a two winding transformer are: For connections between the two systems at very high voltage, where the power is disadvantagess 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. There are also autotransformers in which the secondary intake is achieved through a sliding brush, allowing a continuous range of secondary voltages ranging from advatnages to the voltage of the source.

Views Read Edit View history. Hence the auto disadvantates is used when the value of K is nearly equal to unity. 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.

This means that a greater amount of power can be transferred without exceeding the current rating of the windings of the transformer.

The autotransformer serves a function similar to that of the ordinary transformer to raise or lower voltage. This power is the component of the power transferred by transformer autotransformre or by electromagnetic induction. A part of the winding is common to both primary and secondary sides.

A special form of autotransformer called a zig zag is used to provide grounding on three-phase systems that otherwise have no connection to ground. 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 auttotransformer 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.

Neglecting voltage drops in the windings. This system increases usable transmission distance, reduces induced interference into external equipment and reduces cost. Please disable your adblocking software or whitelist our website. The variable ratio of the autotransformer compensates for the voltage drop along the line.

The tapping may be fixed or variable.


The ” auto ” Autotraansformer for “self” prefix refers to the single coil acting alone, not to any kind of automatic mechanism. Therefore the auto-transformer requires much highs standard of insulation compared to normal transformer. The supply voltage is applied across AB, and the load is connected across CB.

What is an Auto Transformer? – Working, Advantage, Disadvantage & Uses – Circuit Globe

From Wikipedia, the free encyclopedia. By exposing part of the winding coils and making the secondary connection through a sliding brusha continuously variable turns ratio can be obtained, autotransformre for very smooth control of output voltage.

Improving your life knowledge health and family. There are various advantages of the auto transformer, but then also one major disadvantage, why auto transformer is not widely used, is that. This last design was commercialized in the United States under the generic name of Variac and in practice it works as a source of alternating current in tension. There are two types of auto transformer based on the construction.

Autotransformer – Wikipedia

They require alternating currents to operate properly and will not function on direct current. Leave this field empty. This situation must be taken into account when deciding to use an autotransformer for a certain application.

The current ratings of the windings are given by. The advantages and disadvantages of autotransformers will be explained below. As in the ordinary transformer, the primary and secondary ampere-turns balance each other, except for the small current ad for core magnetization: The apparent power transformed by induction is. We call the total current of vacuum I0, as we have done autotransformeer other opportunities.

In three phase power transmission applications, autotransformers have the limitations of not suppressing harmonic currents and as acting as another source of ground fault currents.

In the same way as transformers, autotransformers can also be equipped with automatic tap changers and used in transmission and distribution systems to regulate the voltage of the electric network. In other projects Wikimedia Commons.