Auto transformer definition

In this topic, you study Three Phase Auto Transformer. For transformation of polyphase voltages, it is preferable to use auto transformers instead of two winding transformers in case the voltage ratio is not greater than 2. The auto transformers in three phase circuits can be connected in many different ways using a bank of three identical single phase auto transformers or three phase three limbed core type auto transformers. But most commonly used connection is a star connection. Fig. 1 (a) shows a star connected three phase auto transformer and Fig. 1 (b) shows its phasor diagram. This star connected three phase auto transformer behaves like a Yy connected two winding three phase transformer in many respects. Fig. 1: (a) Star connected three phase auto transformer, (b) Its phasor diagram Applications of Three phase Auto transformers Three phase auto transformers have numerous applications, principle among them are listed below: (i) Small and medium-sized three phase auto transformers are very economical and are satisfactory for a variety of purposes such as • For obtaining three phase variable output voltage for testing and laboratory purposes. When used for this purpose, they are in the form of a three phase variable-ratio auto transformer commonly known by its trade name as three phase variac (Fig. 2). Fig. 2: Schematic diagram of three phase variac • As auto transformer starters for starting of three phase induction and synchronous motors at reduced voltages. (ii) Lar...

An autotransformer is a transformer having part of its winding included in both the input and output circuit. A simple autotransformer connection is shown in Fig. 1. Note that because there is a common portion of the winding (Section 1-2), there is no isolation between the input and output circuits. Also note that there is only one winding. As shown in the diagram, the line current is 10A for a 2000VA output (10A x 200V). The load current is 20A at 100V or 2,000VA output. The winding is tapped at 100V so that the autotransformer functions as a 200V-to-100V stepdown transformer. While this is an acceptable transformer connection, its application is rather limited because of the absence of isolation between input and output circuits. Note that the load current flows in the opposite direction as the line current, which is typical in all transformers. The current in Section 1-2 is, therefore, the difference between these two currents, or 10A (20A load minus 10A line). Calculating equivalent size The equivalent size of the autotransformer in the diagram below can be found as follows. Section 2-3 VA equals 100V times 10A, or 1,000VA. Section 1-2 VA equals the quantity of the load current minus the line current times 100V[(20A-10A) x 100V], or 1,000VA. Therefore, the equivalent physical size is equal to Section 1-2 VA plus Section 2-3 VA, divided by 2[(1,000VA + 1,000VA)/2], or 1,000VA. Thus, we have a transformer whose equivalent size is 1,000VA but supplies a load of 2,000VA. A...

Outline • • • • • • • • • • • • • • • • • • • • • • • • • • • • Introduction The Transformers are electromagnetic devices that transfer electrical energy from one circuit to another by principle of mutual induction. Mutual induction is the coupling of inductances by their mutual magnetic fields. For example in a single-phase transformer there are two coils, a primary and a secondary coil. The primary coil will get the power from any electrical source like an AC generator. The magnetic field produced by the primary induces a voltage into the secondary coil. This secondary coil will be connected to the load and gets the supply accordingly. Transformers are used to increase the voltage up to a higher level and they are called step up transformers. In the same way the transformers decreases the voltage down to a lower level and they are called as Step down transformers. What is an Autotransformer? As stated above a normal transformer will have two windings which are physically separated but magnetically coupled together with the help of a magnetic core. As they are separately been isolated, they are called as primary winding which receives the voltage from the source and secondary winding which transfers to the output load. But the transformer in which there will be only one winding which is common to both primary and secondary is called Autotransformer. The term Auto here refers to that the voltage input variations will be automatically can be improved or can be reduced utili...

In this topic, you study Auto transformer – Theory, Diagram, Advantages & Applications. An auto transformer is a transformer having only one winding wound on a laminated magnetic core, the part of this winding being common to both the primary and secondary circuits. As an ordinary two winding transformer, it can be used as a step-down or a step-up transformer as illustrated in Figs. 1 (a) and (b) respectively. (a) (b) Fig. 1: (a) Step-down auto transformer, (b) Step-up auto transformer In Fig. 1 (a), the winding AC forms the primary and its portion BC forms the secondary On the other hand, in Fig. 1 (b), the winding AC forms the secondary and its portion BC forms the primary. The performance of the auto transformer is governed by the same fundamental considerations which we have already discussed for the two winding transformers. Hence, in the case of an auto transformer also, neglecting the losses, the leakage reactance and the magnetizing current, we have \[\frac\] …(With usual notations) Saving of Copper For the same capacity (i.e. output) and voltage ratio, the auto transformer requires less copper than a conventional two winding transformer. This can be easily verified as follows. For any winding, Cross-section of conductor ∝ Current carried, I Total length of conductor ∝ Number of turns, N Hence, Volume of copper or the weight of copper ∝ NI Now, let us use this relationship to compare the requirement of copper in the case of an ordinary two winding transformer and t...

• - Select - • 简体中文 (Chinese - Simplified) • 繁體中文 (Chinese - Traditional) • Español (Spanish) • Esperanto (Esperanto) • 日本語 (Japanese) • Português (Portuguese) • Deutsch (German) • العربية (Arabic) • Français (French) • Русский (Russian) • ಕನ್ನಡ (Kannada) • 한국어 (Korean) • עברית (Hebrew) • Gaeilge (Irish) • Українська (Ukrainian) • اردو (Urdu) • Magyar (Hungarian) • मानक हिन्दी (Hindi) • Indonesia (Indonesian) • Italiano (Italian) • தமிழ் (Tamil) • Türkçe (Turkish) • తెలుగు (Telugu) • ภาษาไทย (Thai) • Tiếng Việt (Vietnamese) • Čeština (Czech) • Polski (Polish) • Bahasa Indonesia (Indonesian) • Românește (Romanian) • Nederlands (Dutch) • Ελληνικά (Greek) • Latinum (Latin) • Svenska (Swedish) • Dansk (Danish) • Suomi (Finnish) • فارسی (Persian) • ייִדיש (Yiddish) • հայերեն (Armenian) • Norsk (Norwegian) • English (English) The ASL fingerspelling provided here is most commonly used for proper names of people and places; it is also used in some languages for concepts for which no sign is available at that moment. There are obviously specific signs for many words available in sign language that are more appropriate for daily usage. Nearby&relatedentries: • • • • • • • • • • Alternativesearchesfor auto-transformer: • Search for auto-transformer • Search for auto-transformer • auto-transformer • Search for auto-transformer • Search for auto-transformer • Search for auto-transformer • Search for auto-transformer • auto-transformer? • Search for auto-transformer • Search for Amazon ...

The auto transformer working principle and construction is similar to that of conventional two winding transformers. However, it differs in the way in which the primary and the secondary are inter-related. In a two-winding Auto Transformer Working Principle The circuit diagram of an auto transformer is shown in Figure given below. When the single phase AC supply is connected between A and D terminals and output is taken from C and E terminals, this auto transformer will operate as a step-down transformer. Because the number of turns in winding between A and D terminal (i.e. primary winding) is more than the number of turns in winding between C and E terminal (i.e. secondary winding). On the other hand, when the single phase AC supply is connected between B and D terminals and output is taken from C and E terminals, the same auto transformer will operate as a step-up transformer. Because the number of turns in winding between B and D terminal (i.e. primary winding) is less than the number of turns in winding between C and E terminal (i.e. secondary winding). We can make small variations in output voltage by taking the output from different tapings of the auto transformer. I 1 – I 2). Therefore, the cross-sectional area of that winding wire is minimum. Electrically Transformed Energy in Autotransformer In an autotransformer, energy is transformed into the load by two means, electrically as well as magnetically (or inductively). It can be proved that power transformed inducti...