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Transformer Built In Protection and Cooling Tutorials

Protection Devices Built In For Safe Operation of A Transformer

Conservator
It is a sort of a drum, mounted on the top of transformer. A level indicatoris fixed to it. Conservator is connected through a pipe to the transformer containing oil. This oil expanse and contracts depending upon the heat produced so the oil level in the conservator rises and falls. Pipe connected to the conservator is left open to the atmosphere through a breather so that extra air any go out or come in.

Breather
Is is a box containing calcium chloride to absorb moisture of air entering the conservator as it sis well known fact that the insulating property of the transformer oil is lost even if a small amount of moisture enters in it, so the dry air is allowed to pass in through this breather.

Temperature Gauge
It is fitted to a transformer which indicates the temperature of transformer oil.Explosion Vent
It protects the transformer tank from the gases induced by any type  of short circuit in the transformer.

Pipes
These are fitted for cooling the transformer oil. The hot oil circulates through these pipes where it becomes cool due to the air touching.

Important Facts About Transmission and Distribution Transformer
1. Eddy current losses in a transformer are minimised by laminating the core, the lamination being insulated from each other by a light coat of core plate varnish.
2. The basic property of the transformer is that it changes the voltage level of an alternating current signal without changing power, frequency or shape.
3. The primary and secondary voltages are 180 degree out of phase in transformer.
4. Eddy current lossesin transformer core are reduced by decreasing the thickness of laminations.
5. The resistance of low voltage side of a transformer is less than the resistance of its high voltage side.
6. The efficiency of a transformer is normally in the range of ninety ot ninety eight percent.
7. The reactance of transformer is determined by its leakage flux.
8. The principle of working of a transformer is mutual induction.
9. Transformer is used to change the valuesof voltage.
10. The path of the magnetic flux in a transformer has low reactance.
11. Electric power is transformed from one coil to the other coil in a transformer magnetically.
12. Ideal transformer assumptions do not include zero reactance of windings.
13. Preferably, the resistance between the primary and the secondary of a transformer should be as low as possible.
14. The main function of the iron core in a transformer is to decrease the reluctance of the magnetic path.
15. Magnetic circuit is common in the two windings of a transformer.
16. A transformer operates at power factor depending on the power factor of the load.
17. The lamination are made from nickel alloy steel stampings.
18. The steel for construction of transformer core is made so as to have high permeability and low hysteresis.
19. The special silicon stell in used for laminations because hysteresis losses are reduced.
20. Power transformer are designed to have maximum efficiency at near full load.

Cooling Of Transformer

Natural Cooling
The cooling is provided through natural circulation of air. The surface area of the core and the transformer winding are sufficient to dissipate the heat generated. It is used for small transformer from ten kva to fifteen kva.

Natural Oil Cooling
The transformer is placed in tank filled with oil known as transformer oil. The oil used in the tank not only helps cooling the transformer but also provides insulating for the winding. The oil takes the heat produced by the transformer, the oil circulate through the pipes and tank. The hot oil becomes lighter in weight and goes up from where comes down through pipes to the bottom of the tank after cooling. The oil level should never fall below the upper ends of pipes.

Oil Blast Cooling
In this method radiator tanks are provided to the side walls of the main tank. The oil circulators through these radiators from the main tank. The radiator tanks are cooled by air blast. The system of cooling is known as oil blast type. It is used for transformer rated above five hundred kva.

Force Water Cooling
The winding of transformer is placed inside the tank containing oil and cold water is passed through the copper pipe spiral kept in the transformer oil. The cold water absorbs and carrier away the heat of the oil. The pressure of the water is not kept greater than the pressure of the oil in the tank because in case of leakage in the pipe, the water will enter into the oil. It is used for transformer having output greater than five hundred KVA.

Force Air Cooling
In this method the air is first filtered to eliminate moisture and dust particless and this filetered air under pressure is forced to passed through the winding care of the transformer and the dusts provided in them. This method is used where there 
is a scarcity of water.

1 comment:

Electrical Inspections said...

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Electrical Inspections

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