TRANSFORMER Objectives of Transformer Definition Of Transformer Construction

TRANSFORMER

Objectives of Transformer �Definition Of Transformer �Construction Of Transformer �Working Operation Of Transformer �Types Of Transformer �Autotransformer

Definition of Transformer TRANSFORMER is a static device which is used to transfer electrical energy from one AC circuit to another AC circuit, with increase/decrease in voltage but without any change in frequency. (AC Input) (Change in Volt. , no change in frequency)

1. Functions & Uses of Transformer ►The Electrical energy is generated at extremely high Voltages, Thus Voltage is reduced for Industrial uses. ►This is done by using Transformers (Step Down Transformer). ►We can also use Step Up transformer to increase the level of Voltage. ►When Voltage level is changed, there is change in current level also.

2. Power Transmission System Generating Station (5 KV) Step Up Transformer ( 220 KV) Step Down Transformer (11 KV)

3. Construction Of Transformers

Construction(cont…) 1. It consists of two windings wound around an iron or steel core. 2. Winding connected to ac supply is called as Primary winding whereas the other one is called as Secondary winding. 3. Both windings are isolated to each other through core. 4. Both coils are magnetically coupled.

4. Working Operation Of Transformers As AC supply is connected , an AC current starts flowing. AC primary current produces an alternating flux (ø) in the core. This flux gets linked with secondary winding through core. This flux will induce voltage into secondary winding due to mutual induction. Hence, EMF induced in secondary winding is mutually induced EMF.

5. Important parts of Transformers 1. The Copper Windings(Coils) 2. The Silicon Laminated Core 3. Suitable Tank 4. Conservator 5. Bushings 6. Breather 7. Explosion Vent

6. Types Of Transformers Step Up Transformer Step Down Transformer Shell Type Transformer Core Type Transformer

7. Step Up & Step Down Transformer �Step up Transformer: Transformer having N 2>N 1 is Step up Transformer. �Step down Transformer: Transformer having N 1<N 2 is Step down Transformer. �One-to-one Transformer: Transformer having N 2=N 1 is called One-to-one X-Mer.

8. Core Type Transformer

Important points about Core Type Transformers �Core is in form of rectangular frame. �It provides a single magnetic circuit. �Both windings are uniformly distributed on 2 limb of core. �Windings are in cylindrical shape and arranged in concentric manner with low voltage winding placed near the core.

9. Shell Type Transformer

Important points about Shell Type Transformers �Both windings are placed on central limb of core. �High & low voltage windings are of sandwich type. �This type of Transformer provides better mechanical support and protection for windings. � Cooling is not very effective.

10. Comparison between Core Type & Shell Type Transformer. Core Type Transformer Shell Type Transformer � 1. Windings encircles the core. 1. Core encircles the windings. � 2. This Type is easy to repair. 2. This is not so easy to repair. � 3. Cylindrical windings are used. 3. Sandwich type windings are used. � 4. Less mechanical protection to 4. Better mechanical protection to coils(windings). � 5. Better cooling since more 5. Cooling is not very effective. surface is expose to atmosphere.

Why Transformer should never be connected toisd. c. supply? magnitude. Direct Current of constant Due to this, flux produced in core is of constant value. Hence, Induced EMF in secondary winding is zero. If dc is applied , there is possibility of core saturation. If core saturates primary winding will draw excessive large current. Hence, DC should be avoided.

11. Auto Transformer

Important points about Autotransformers. 1. Two winding Transformer has separate primary & secondary winding. 2. But In Autotransformer a part of winding is common for primary & secondary. 3. It consists of one winding wound around a laminated core, with a rotary movable contact. 4. Autotransformer can operate on Step Up as well as Step down Transformer.

12. Autotransformer as a Step Up 1. Note that the part CB of the complete winding acts as a primary winding. 2. The ac input voltage V 1 is applied between terminals C & B. 3. The full winding acts as a secondary winding and load is connected between these terminals. 4. As N 1 -Secondary winding i. e. CB is higher than the N 2 -Primary winding i. e. AB, Auto Transformer acts as a Step Up Transformer.

13. Autotransformer as a Step Down 1. Note that the part CB act as the secondary winding. 2. The ac input voltage V 1 is applied between terminals C & B. 3. The full winding AB acts a primary winding and load is connected between these terminals. 4. As the N 1 -Primary winding i. e. AB is less than N 2 Secondary winding i. e. CB, Autotransformer is Step down.

14. Advt. & Disadvt. Of Autotransformer Advantages Disadvantages • • • No isolation between N 1 & N 2 is dangerous for high voltage application. • If secondary winding is short circuited, then large current will flow on the secondary side. Less copper required. Size & hence cost is reduced. It has a high efficiency. Due to reduced resistance, Voltage regulation is better.

15. Comparison between 2 winding & Autotransformer � 1. Primary & Secondary winding. � 3. It can operate as step up or step down transformer. � 1. Part of winding is common between primary & secondary winding. � 2. There is movable contact. � 3. It can operate as step up as well as step down transformer. � 4. It can be used as Power supply, welding, isolation transformer. � 4. It can be used as Variac, for starting of ac motor, Dimmer stat. � 2. No movable contact.

16. Transformer Development Timeline In 1881, Charles F Brush develops his own design of Transformer. In 1882, Sebastian Ferranti with William Thomson design earliest AC power Transformer. In 1886, William Stanley makes Transformer more practical due to some design changes. In 1888, Albert Schmid, improved Stanley's design, extending e-shaped plates to meet a central projection.

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