In an autotransformer, the common portion of the single winding acts as part of both the “primary” and “secondary” windings. The remaining. Auto-transformer Advantages: Auto-transformers in comparison with the double winding transformers are generally advantageous of the. ADVANTAGES OF AUTO TRANSFORMER STARTER: a) On the 65% tapping the line current is approximately equal tp that of a Star-Delta.

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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.

This situation must be taken into account when deciding to use an autotransformer for a certain application.

Equation 4 may also be written as. 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.

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.

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 diszdvantages 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.

Autotransfodmer large part is merely transferred electrically by conduction.

There are two types of auto transformer based on the construction. The construction of Auto transformer is shown in the figure below.

Autotransformer Advantages and Disadvantages – LORECENTRAL

When a voltage V 1 is applied to the primary of the autotransformer, the induced voltages are related by. The transfer of power between two circuits connected to an autotransformer occurs through two phenomena: An electrical connection between aautotransformer primary and secondary is not always desirable, particularly when the voltages levels on both the sides of transformer are quite different.


Transformers limited general conditions of transport manufacturing capacity constraints, limitations in the same conditions of transport, under the same conditions of carriage, autotransformer capacity larger than the two-winding transformer manufacturing. Note that if the turns ratio of the transformer is large, the power rating as an autotransformer will be much larger than the rating as a conventional transformer.

Some of the disadvantages of an autotransformer are: The advantages and disadvantages of autotransformers will be explained below. Ordinary Two Winding Transformer.

Auto-Transformers Advantages Disadvantages

Other advantages of an autotransformer over a two winding transformer are: Surge Arrester protection is required As the short circuit impendace values of the auto-transformer are low, short circuit currents can reach higher critical values. Disadvabtages autotransformer be used as a step-up transformer. 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 voltage winding.

In an autotransformer, the total power transmitted from the primary to the secondary does not actually pass through the whole winding. There are autotransformers with several sockets in the secondary and therefore, with several transformation ratios. One of the coil terminals is common to both input and output, and the other output terminal is movable so that it can make contact with any turn on the winding.

Substituting Equation 5 into Equation 3the ratio of the winding current is found as. However, the apparent power in the transformer windings is. As a step-up, it is often referred anc as a boost, and as a step-down, it is called a buck connection. The weight of the copper is proportional to the length and area of a cross section of the conductor.

Find Free WordPress Themes and plugins. Since it is the same capacity of two-winding transformer light weight, small size, covering an area of small.


There are very important applications for the operation of other machines that require autotransformers. In this way we have a more effective AC machine. Figure 1 shows the schematic representation of buck connection while figure 2 shows the boost connection.

It consists of a single continuous winding with a tap brought out at some intermediate point as shown in Fig. In general practice, auto transformers are only used on distribution systems where the neutral is disadvanrages to the earth Auto-transformers are particularly sensitive to the atmospheric over-voltages.

Autotransformer Advantages and Disadvantages

Because transformer silicon steel sheet and copper is and an inductive winding rated voltage and rated current, and related to the capacity of the winding, autotransformer winding capacity reduced material consumption is reduced, and low cost.

A part of this induced emf is taken in the secondary circuit. Its main applications area is power transmission and distribution, audio system, and railways.

An auto transformer is similar to a two winding transformer but differ in the way the primary and secondary winding are interrelated.

On load condition, a part of the load current is obtained directly from the supply and the remaining part is obtained by transformer action. The apparent power transformed by induction is. This means that a greater amount of disadvamtages can be transferred without exceeding the current rating of the windings of the transformer.

This will not be possible with normal transformers Auto-transformer Disadvantages: Ahmed Faizan Sheikh, M. Your email address will not be published. Hence, saving in copper increases as the transformation ratio approaches to unity. An A uto Transformer is a transformer with only one winding wound on a laminated core. As the secondary ampere-turns are opposite to primary ampere turns, so the current I 2 is in phase sutotransformer to I 1.

The secondary voltage is less than the primary.