8. Transformers
What is an Electric Transformer?
The transformer is a static device that consists of one,
two or more windings which are magnetically.
It transfers the electrical energy from one circuit to
the other by electromagnetic induction principle.
10. Classification of Transformers
•Transformers are classified into two types based on
the conversion of voltage level. These are step-up
and step-down transformer. These are step-up and
step-down transformers.
11. Step-up Transformers
In step-up transformer, the secondary voltage is more
than the primary voltage. This is due to the lesser
number of coils in the primary compared to the
secondary. This type of transformer is used to raise
the voltage to a higher level. These are used in
transmission systems and are rated at higher power
levels
12. Step-down Transformers
In step-down transformer, secondary voltage is less
than the primary voltage due to the less number of
turns in the secondary winding. so, this type of
transformer is used to reduce the voltage to specified
levels of the circuit. . These types of transformers are
used in (power transformers) and in (electronic
transformers).
15. Cooling methods of Transformers
Transformer can be divided in two types as :
•(i)Dry type transformers
1-Air Natural(AN).
2-Air Blast.
16. Cooling methods of Transformers
(ii)oil immersed transformers
1-Oil Natural Air Natural (ONAN)
2-Oil Natural Air Forced (ONAF)
3-Oil Forced Air Forced (OFAF)
4-Oil Forced Water Forced (OFWF)
17. losses in transformer
The transformer has no moving parts and hence the
mechanical losses are absent in it. Hence, the losses
in the transformer are considered as electrical energy
losses. Two types of electrical losses are exist in a
transformer which are core losses and copper losses.
18. substation bus-bar systems
There are many different electrical bus system
schemes available but selection of particular scheme
depends on:
(a) the system voltage.
(b) a position of substation in electrical power system.
(c) Flexibility needed in system and cost.
(d) Simplicity of system.
19. Single Bus System
Single Bus System is simplest and cheapest one.
All the feeders and transformer are connected to only
one single bus.
Reliability of the single bus configuration is low.
Advantages of Single Bus System:
1-simple in design. 2-low cost. 3-easy to control.
Disadvantages of Single Bus system:
Low reliability.
20. Double Bus Double Breaker System
Any circuit breaker can be removed for maintenance
without interruption of the corresponding circuit.
Advantages of double Bus double breaker System:
1-If we have Damage can feed from anther bus.
2-it has high reliability.
Disadvantages of double Bus double breaker system:
It is costly and need more space.
