Different Types of Transformers
Transformers can be classified on different basis, like types of construction, types of cooling etc.(A) On the basis of construction, transformers can be classified into two types as;
(i) Core type transformer and (ii) Shell type transformer, which are described below.
In core type transformer, windings are cylindrical former wound, mounted on the core limbs as shown in the figure above. The cylindrical coils have different layers and each layer is insulated from each other. Materials like paper, cloth or mica can be used for insulation. Low voltage windings are placed nearer to the core, as they are easier to insulate.
(Ii) Shell Type Transformer
The coils are former wound and mounted in layers stacked with insulation between them. A shell type transformer may have simple rectangular form (as shown in above fig), or it may have a distributed form.
(B) On the basis of their purpose
Step up transformer: Voltage increases (with subsequent decrease in current) at secondary.
Step down transformer: Voltage decreases (with subsequent increase in current) at secondary.
(C) On the basis of type of supply
1.Single phase transformer
2.Three phase transformer
(D) On the basis of their use
1.Power transformer: Used in transmission network, high rating
2.Distribution transformer: Used in distribution network, comparatively lower rating than that of power transformers.
3.Instrument transformer: Used in relay and protection purpose in different instruments in industries
Current transformer (CT)
Potential transformer (PT)
(E) On the basis of cooling employed Oil-filled self cooled type
Oil-filled water cooled type
Air blast type (air cooled)
