What is Transformer?
The transformer is a static device means a transformer is not having any rotating parts in its operation. The transformer transfers electrical energy from one electrical circuit to another electrical circuit. The transformer increase (step-up) or decreases (step down) the voltage and current as per requirement without changing the frequency.
The transformer has primary and secondary winding and an iron core. The transformer also has LV and HV bushing, Buchholz relay, conservator tank, radiators etc.
1. Power Transformer
2. Distribution Transformer
3. Step-Up Transformer
4. Step Down Transformer
5. Core Type Transformer
6. Shell Type Transformer
7. Current Transformer
8. Potential Transformer
9. Auto Transformer
10. Constant Voltage Transformer
11. Electromagnetic potential transformer
12. Phase Shifting Transformer
13. Isolation Transformer
14. Grounding Transformer
15. Toroidal Transformer
16. Step Voltage Regulators
17. Berry Type Transformer
18. Air core Transformer
19. Dry type transformer
20. Single Phase Transformer
1. Power Transformer
The power transformer is installed at various power stations and substations for the generation of electrical power and transmission of electrical power. The power transformer is used for ratting above the 200MVA means power transformers are used for higher ratting. The power transforemers are oil immersed transfomers. The primary and secondary widings and core of the transformer are immersed in isulating oil.
The power transformer is utilized in transmission networks and used for higher voltages. The power transformer is designed for the maximum efficiency of 100 %. The power transformers are very larger in size.
The power transformer has the ratting 33Kv, 66Kv, 110Kv, 132Kv, 220Kv, 400Kv, 765Kv. In transmission networks, the power transformers always operated at full load.
In power transformers, copper loss and iron losses are takes place throughout the day. In a power transformer, the flux density is very higher. The power transformer is used for interconnecting the two power stations.
The power transformer is used in generating stations and transmission substations. The power transformer is used for stepping up or stepping down the voltage and current without changing the frequency.
2. Distribution Transformer
The distribution transformer is used to step down the voltage and current which is supplied by the power transformers. The primary voltage of the distribution transformer is supplied from the power transformer secondary and it is 11Kv or less. The primary voltage of the distribution transformer is used by domestic and industrial consumers. The secondary voltage of the distribution transformer is 440 or 230V depending upon the requirement.
The distribution transformer is one type of step down transformer which is stepping down the higher transmission voltage to a lower voltage that can be used by the consumer.
The Voltage level of the distribution transformer is 11Kv, 6.6Kv, 3.3Kv, 440V and 230V. The distribution transformer is smaller in size. The distribution transformer is designed for 50 - 70 % efficiency. The flux density in the power transformer is very less. In distribution transformer, iron loss takes place throughout the day.
The distribution transformer is used in distribution networks for lower voltages. The distribution transformer used for the ratting is less than 200MVA. The distribution transformer is used in distribution stations and also for industrial and domestic purposes. The distribution transformer is used for end-user connectivity.
3. Step Up transformer
A transformer which is converts low voltage and High current from its primary side to high voltage and low current from its secondary side is called a step-up transformer. The step-up transformer is used for transmission and generation of electrical power. A transformer which is having higher output voltage than the input voltage is called a step-up transformer.
The high voltage winding of the step-up transformer consists of a large number of turns of thin wire as compared to low voltage winding. The low voltage winding consists of less number of turns of thick wire because low voltage winding consists of a larger current as compared to high voltage winding.
In a step-up transformer, low voltage windings are placed near to the transformer core and high voltage winding is placed above the low voltage winding.
The step transformer consists of larger transformation ratios. The voltage produced in generating plant is very low and this voltage is increased by using the step-up transformer and transmitted over long distances.
4. Step down the transformer
A transformer which converts the high voltage and low current to the primary side to the low voltage and higher current to the secondary side is called a step-down transformer. The step-down transformer is used for transmission and distribution purposes. A transformer which has a lower output voltage than the input voltage is called a step-down transformer.
The high voltage winding is the Primary winding of the step-up transformer. The Primary winding consists of a larger number of turns of thin wire because primary winding has lower current and higher voltage.
The low voltage winding is the secondary winding of step down transformer. The secondary winding consists of a lesser number of turns of thick wire because secondary winding has lower voltage and higher current.
The transformation ratio of a step-down transformer is equal to the voltage ratio. This transformer is used for distribution purposes.
5. Core type transformer
The core of a single-phase transformer is a single-window core and has two limbs only. The magnetic core of the transformer is made from L shape laminations and forms a rectangular shape. The high voltage and low voltage windings are wrapped around the core. In the core type transformer, windings surround the core.
The high voltage and low voltage winding are divided into two parts and half parts of both the windings are wound on one limb and the second-half part of both the windings are wound on other limbs.
The low voltage winding is first wrapped on the core surface with sufficient insulations between the core and low voltage windings. After low voltage winding, high voltage windings are wrapped with sufficient insulation between the low voltage windings and high voltage windings. the windings used in core type transformer are square, cruciform and two or three stepped. In this way, both the limbs are covered with low voltage and high voltage windings.
6. Shell type transformer
There are E's and L's shape laminations used to make the core of shell type of transformer. the core of the single-phase transformer is made with three limbs or legs. the mechanical strength of the core is increased by this design and also improves the protection of transformer windings from external mechanical shocks or vibrations. The high voltage and low voltage windings are wound around the central limb.
In a shell-type transformer, the core encircles the windings of the transformer. the central limb of the core carries the entire flux and the side limb of the transformer carries half of the flux. Hence the width of the central limb is two times the side limbs. The mechanical strength of the shell-type transformer has more due to bracing as compared to the core type transformer.
The magnetic flux flows through the one closed path which reduces the core losses or iron losses of the transformer and hence increases the efficiency of the transformer. The high voltage and low voltage winding are wound on the central limb of the core. the low voltage windings are placed near to the core and high voltage winding are placed outside the low voltage winding. which is reduce the insulation cost between the low voltage winding and core.
7. Current Transformer
The large alternating current which can not be sensed or passed through the normal ammeter and current coils of wattmeters, energy meters can easily be measured by use of current transformer along with normal low range instruments.
A transformer is a device that consists of two windings called primary and secondary windings. It transfers energy from one side to another side with a suitable change in the level of current or voltage.
The current transformer is a device that is used to convert higher value current to lower value current. the current transformer is used to convert high voltage current to low voltage current which can easily be measured by an ammeter. In a current transformer current in the primary is proportional to the current in secondary windings. the current transformer is used for measuring high voltage current because metering instruments like ammeters have difficulty with insulations. the current transformer is used to measure a high voltage current up to 100 meters.
8. Potential transformer
A potential transformer is an instrument transformer that is used to step down the higher-level voltage to lower-level voltage that can easily be measured with help of instruments like a voltmeter, Wattmeter and watt-hour meter.
The potential transformers are accurate ratio step down transformers. The potential transformer has low power rating windings.
The potential transformer consists of primary windings with a large number of turns of copper wire and secondary winding consists of less number of turns which is rated for 110V.
The primary winding is connected to the high voltage transmission line where voltage can be measured and secondary windings are connected to the low range voltameter coil. One end of the secondary winding is always earthed for safety purposes. to prevent secondary winding from reaching dangerous potential, the end secondary winding of the potential transformer is earthed.
9. Auto Transformer
The normal power transformer has different primary windings and secondary windings. But the autotransformer is a special type of transformer in which a part of the winding is common for the primary and secondary windings. In ordinary power transformers. primary and secondary windings are insulated with proper insulation and connected magnetically to each other. An autotransformer is the single winding transformer.
In an autotransformer, primary and secondary windings are connected electrically as well magnetically to each other. In an autotransformer transformation ratio is unity. In autotransformers more saving in copper because only one winding is used. The auto transformer is also called two winding transformer.
10. Capacitve Voltage Transformer
The Capacitive potential transformer is a combination of capacitance potential divider and magnetic potential transformer with a small transformation ratio. The capacitor voltage divider is used to lower down the very high voltage to below the 10kV. The capacitors are connected in series on the primary side of the magnetic transformer.
The magnetic transformer again reduced the high voltage to low voltage with high accuracy which can be measured by the voltmeter or wattmeter. Capacitive voltage transformers are used for high voltage power transmission lines.
The capacitive potential dividers, inductive elements and magnetic transformer are the three main parts of a potential transformer.
For measuring high voltages above 100Kv high insulated potential transformer is required. The highly insulated potential transformer has more cost due to more insulation required. The capacitive transformer is cheap because less insulation is required. For reducing the cost, a capacitive voltage transformer is used for higher voltages.
11. Electromagnetic potential transformer
The potential transformer uses the electromagnetic induction principle to convert high voltage to low voltage is called an electromagnetic potential transformer.
The primary and secondary windings of the transformer are wounded around the core, so this type of transformer is also called wound type potential transformer. This potential transformer is shell type or core type and these transformers do not use any electronic component for reducing the secondary voltage such as a capacitor.
The main problem in an electromagnetic transformer is the insulation problem for high voltages. Due to insulation problems in potential transformer for higher voltages above 10kv design become very complex. The electromagnetic transformers are very expensive because of more insulation requirements.
12. Phase Shifting Transformer
A phase-shifting transformer controls the flow of active or real power in three-phase electrical transmission networks. These can be done by changing the phase angle of the voltage of transmission networks. The phase-shifting transformer stabilizes the real power flow and balances the power system load.
Phase-shifting transformer injects the phase-shifted voltage into the transmission line by using a series-connected transformer. The phase-shifting transformer is used for controlling the power demand levels and also boosts the reliability and efficiency of the grid.
13. Isolation Transformer
A transformer is used to provide electrical isolation between the two electrical circuits, primary and secondary without changing the voltage, current and frequency levels are called an isolation transformer.
The number of turns in primary and secondary sides are equal in isolation transformer so, primary voltage also equal to the secondary voltage.The isolation transformer is 1:1 ratio transformer.
The isolation transformer provides the isolation between the two electrically connected system physically as well as electrically. The main function of isolation transformer is reduce the voltage surges in transmission lines. The isolation transformer protects the electronic circuit from voltage surges and also protect the persons from shock from electrical transmission lines.
The construction of isolation is similar to the normal core type type transformer. The primary winding are completely isolated from the secondary winding.
14. Grounding Transformer
In delta- delta connected transformer neutral is not available. The grounding transformer is used to provide the neutral where it is not available. The grounding transformer is also called earthing transformer. The earthing transformer is provides low impedance path to the neutral to the earth.
The overvoltages produced by arcing ground, lightning surges are eliminated by the earthing transformer by discharging to the earth.
15. Toroidal Transformer
Toroidal transformer is one type of power transformer which is having toroidal core on which the primary and secondary winding are wound.
When the current flowing through the primary winding electromagnetic flux is produced. This electromagnetic flux induce the current in the secondary winding of traformer. By this way, power is transferred from the primary winding to secondary winding.
The toroidal transformer having higher efficiency, compact in size, less audible noise and hum as compared to the normal transformers.
The toroidal transformer is mostly used in electronic devices like audio devices. Toroidal transformers are one type of inductor.
16. Step Voltage Regulators
The step voltage regulators are one type of transformer in which high voltage winding is connected in shunt and low voltage winding is connected in series. The step voltage regulator either aids or opposes their respective voltages.
The step voltage regulators are used to boost the voltage in a long feeder where voltage changes slowly.
17. Berry Type Transformer
A transformer whose core looks like one type of spokes of a wheel is called a berry type transformer. A berry type transformer is a shell type transformer. A berry type transformer having distributed magnetic circuit. A berry type transformer has more than two magnetic circuits.
Due to more number of magnetic circuits, berry type transformer has more leakage flux than a normal transformer. So berry transformer has less efficiency than the normal core type and shell-type transformer.
The berry type transformer is only used for making high capacity transformers.
18. Air core Transformer
When we supplied alternating current to the coil, electromagnetic flux produced in the coil and surrounding the coil. When we brought another coil inside the magentic filed of first coil, the eletro motive force(emf) is induced in another coil.
The Induced emf is used to supply a load. In this arrangement flux is linked in both the coil through the air. So this arrangement is known as air core transformer. In this arrangement first coil is used as primary winding and second coil used as secondary winding. The air core transformer uses a air as a core of transfomer.
The application of air core transformer
1. Air core transformer is used for changing the voltage level from one level to another level in power system.
2. The air core transformer is used as isolation transformer for isolating a one circuit from another circuit.
3. The air core transformer are used at radio frequency.
19. Dry type Transformer
A dry type transformer does not uses any insulating liquid. The winding and core of transformer are not immersed in the oil. In dry type transformer winding and core of transformer are sealed in pressurised air tank.
Dry type transformer has two types namely
1. Cast resin dry type transformer
2. Vaccum pressure impregnated transformer
1. Cast resin dry type transformer
The core, primary and secondary winding of transformer are sealeded with the epoxy resin. This type of transformer are used in high moisture area. The rating og cast resin dry type transformer 25KVA to 12500 KVA.
2. Vaccum Pressure impregnated transformer
The primary and secondary winding of transformer is sealeded in vaccum protective box. The moiture protectin is very high and these type of transformer never get affected by the moisture. The ratting of transformer is 5KVA to 30KVA.
The dry type transformer is used fire risk areas like forest, chemical industry, gas industry.
20. Single Phase Transformer
A transformer which is operates on single phase power is called single phase transformer. The single phase transformer consits of one magnetic core, primary winding and secodary winding which all are immersed in insulating power oil. The efficiency of single phase transformer is very high because losses in single phase transformer is very less.
The single phase transformer is used in comercial application and also used in electronics devices.