what is transformer its types, safety ,tests and its efficiency.

Object Required

Transformer

Principle

Determind types, safety and efficency of transformers.

Theory

Transformers :- Transformer is static device used for transfer of electric power from one circuit to another circuit without any electrical connection between them. and without changing ferquency. ( by mutual induction).
Types of transformers:- Transformers are of various types as discuess below.
1. On the basis of Design.
a. Core type
b. Shell type
c. Air core type transformers.

2. On the basis of Power .
a. Power transformers .
b. distribution transformers .
c. Auto transformers.
d. Single phase transformers

3. On the basis of Cooling.
a. Natural air cooled transformers.
b. Forced air cool transformers.
c. Forced air and water cooled transformers.
d. Oil cooled transformers.

Safety of transformers:-
     Safety of transformers is very essential for safe operation of the transformers and protection of the other equipments from demage. there are many safety of transformers as discussed below.

 a. Buchhloz relay :- It is a gas operated relay with two mercury switches inside it. and it is install in between main tank and conservation tank. the purpose of this realy is to safe transformer for any type of internal fault
when ever any fault accur in side the transformer oil is heated up and and expand and gas generated which first hit the alarm mircury switch and alarm generate if some one trip the transformer than okay if not than the second switch operates and trip the transformer .

b.Silica gel:- This gel is used in transformer to absorb
moisture form the air and dry air put insde the transformer it is installed on the breather . on conservator tank.

c. Winding temperature sensor :- It is also a type of safety of transformer whenever the temperature of the transformer winding raises over its normal value its trips the transformer by sending a comand to trip relay.

Loses of transformer:-  There are three different types of losses:

 a. No-load loss (also called iron loss or core loss): Caused by the hysteresis and eddy currents in the core. It is present whenever the transformer is connected, and independent of the load. It represents a constant, and therefore significant, energy drain.

 b. Load loss (or copper loss or short circuit loss): Caused by the resistive losses in the windings and leads, and by eddy currents in the structural steelwork and the windings. It varies with the square of the load current.

 c. Cooling loss (only in transformers with fan cooling): Caused by the energy consumption of a fan. The bigger the other losses, the more cooling is needed and the higher the cooling loss. These losses can be avoided if operational temperature is kept low by different loss reduction measures.

Tests on a transformer:-  There are two type of tests on a transformer.

a. Open circuit test :- This test is preform to know the iron loses of a transformer. In this test rated primary voltage is applied while secondary is left open. the primary voltage is measured with voltmeter and the load current is measured with ammeter and the power loses is measured with watt meter in this test the secondary  current is very low and neglected and hence the wattmeter reading is all iron loses.

b. Close circuit test:- This test is conduct to determind the cooper loses in a transformer.  in this test the voltage is raised slowly up to rated voltage and the secondary is short circuit with thick wire in this test all wattmeter reading is copper loses. 

Efficiency of transformer:- The efficiency of a transformer, like any other device, is defined as the ratio of useful output power to input power.The percentage efficiency of a transformer is in the range of 95 to 99%. For large power transformers with low loss designs, the efficiency can be as high as 99.7%.

 

Conclusion

* The efficiency of a transformer is maximum when Iron loses= Copper loses. * Selection of a transformer with a too-small rating leads to shortened transformer life due to overheating and excessive winding Ioad losses. * Transformers are also used extensively in electronic products to step down the supply voltage to a level suitable for the low voltage circuits they contain. The * transformer also electrically isolates the end user from contact with the supply voltage. * It is also used in generating stations to rise the voltage level up to a high value. * Safety is also big concern in transformer the safety is prevent the equipment from damage and extend its life . * Transformers is also used for measurement of high voltage and current are called instrumental transformer.

Published Date

01 Mar, 2018