Three phase transformer
Three phase system is used to generate and transmit large amount of power.three phase transformer sar required to set up or step down voltage in various stage of power system network.
Transformer 4 3 phase circuit can be constructed in one of the following:
- three separate signal phase transformer are suitable connected for 3 phase operation.such an arrangement is called a three-phase Bank of transformer.
- a single three phase transformer in which the course and binding for all the three phases are combined in singer structure.
Three phase transformer construction
Construction of the magnetic core of a three phase core type transformer maybe understood by considering three single phase core type transformer position at 120 degree to each other as shown in figure. For simplicity, only the primary winding are shown a. Is balanced 3 phase sinusoidal voltage applied to the windings. If the three legs carrying this flags are must the total flux in the most leg is zero.this lab can therefore be removed because it carries no flux as shown in figure b. This structure is not convenient to build. Usually the structure of figure c with the thrill lives in the same plane is used. This is structure can be obtained from figure b, by eliminating the rocks of section b e and fitting the reminder between section a and c. It can be built using stacked lamination. Each leg carries both low voltage and high voltage windings. Since it is easier to insulate the LV windings from the coast than the HV winding, the lvwindings are placed next to the core with suitable insulation between the core and the LV windings.
Difference between current transformer and power transformer
A current transformer is similar in construction to a power transformer in that it has a magnetic circuit with the primary and secondary winding. There is a considerable difference in the method of operation. In a power transformer the primary winding is continuously energized actors substantially constant voltage,and secondary schenectady to a load varying in impedance within wide limits.the current in the primary winding is determined by the load connected to the secondary. The magnetic flux in the core is substantially constant at all loads.the current transformer is connected in the line in series with the load.Bihar sarkar abhi pura the load determine the current through the primary.the secondary schenectady to unload aur burden which does not vary and the primary current is not affected by the load in the secondary. The current in the secondary is determined by the current in the primary. The magnetic flux in the core varies with the the current in the primary.the flux is determined by the connected bird and the flux density in the core is only a very small fraction of that usually used in power transformer.
Transformer cooling
when a transformer is in operation heat is generated due to power losses in the winding and core losses. The removal of heat is called cooling.
The following method are generally used to cool Transformers:
Air natural cooling
inner dry type self cooled transformer the natural circulation of surrounding air is used for its cooling. The winding are protected from mechanical injury by sheet metal enclosure. This type of cooling is satisfactory for low voltage small transformer up to a few KVA.
Air blast cooling
the dry type forced air cooled transformer is similar to that of dry type cells called transformer with the addition that continues blast of filtered cool air is forced through the core and winding for better cooling. The blast is produced by a fan.
Oil natural cooling
the majority of transformer of medium and large rating have their windings and core emergency in oil which act both as a cooling medium and an insulating medium. Oil immerged transformer are enclosed in sheet Steel tank. The heat produced in the core and winding is passed to the oil.jyada lagta hai rated oil becomes lighter and rise to the top and its place the taken by cool oil from the bottom of the tank.calculate the heat of the oil is transferred to the wall of the tank by natural circulation of the oil.the heat is then transferred to the surrounding atmosphere through natural radiation and convection. Oil grade-schooler and falls to the bottom.
Oil blast cooling
in this type of cooling forced air is directed over cooling element of transformer emerged in oil.
Forced oil and water cooling
in this type of cooling forced oil flow with water cooling of the oil in the external water heat exchanger takes place. This type of calling is similar to ofb cooling except that the heat exchanger uses water instead of air for cooling oil. The water is circulated in the cooling tube placed in the heat exchanger.
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