Electrical transformer is static Electrical machine that converts electricity from an electrical circuit in another and without changing the frequency. The transformer can boost and decrease voltage in a an increase or decrease in current.
Working Principle Of Transformer
The the basic principle that drives the fundamental principle of working of is the process of mutual induction of two windings joined by a common magnetic flux. The image below shows the simplest model of an actual transformer. The basic structure of a transformer is two inductive coils: principal winding, and secondary. The coils are physically separated but are connected magnetically to one the other. Whenthe primary windings are connected to an electrical source that produces alternating voltage, magnetic flux is created by winding . The core is the conduit for the flux to connect with it’s secondary winding. A majority of the flux is associated with the secondary winding. This is known as ‘useful flow or the main flux while the flux that is not linked to the secondary winding is referred to as leakage flux. Since the flux generated is oscillating (the direction of the flux is constantly changing), EMF gets induced in the secondary winding as per Faraday’s law on electromagnetic induction . The emf is referred to as’mutually caused emf’. it has a frequency that is mutually inducing EMF is the same as the frequency of supplied emf. If the secondary winding has a sealed circuit the mutually inducing electricity flows in it and the power is transferred by an existing circuit (primary) to another circuit (secondary).
The Basic Construction Of Transformer
A transformer is made up of two windings that are inductive and a steel core that is laminated. The coils are isolated from one another and also from the core of steel. A transformer can also consist of a tank for core assembly and winding (called as a tank) suitable bushings that be used to connect the terminals, an oil conservator to put oil in the tank of the transformer for cooling reasons, and so on. The image below illustrates the fundamental structure of the structure of a transformer.
In all transformers, the core is made by the assembling (stacking) sheets of steel with a minimum air gap between them (to ensure a continuous magnetic paths). The steel is high silicon content. It is also occasionally, it is treated with heat to ensure high permeability and minimal loss in hysteresis. Laminated steel sheets are utilized to minimize the loss of eddy current. They are cut to the shapes of E,I as well as L. To reduce high reluctance around joints, laminations are stack by rotating the sides of joints. This means that if the joints of the first sheet assembly are placed on front, then the joints of the subsequent assemble remain at back side.
Different Types Of Transformers
Transformers can be classified according to different bases, such as kinds of construction, varieties of cooling, etc.
(A) Based on the type of construction, transformers may be classified into two kinds in the following categories: (i) core type transformer, and (ii) Shell type transformer as described below.
(I) (I) Core Type Transformer
In the core type transformers, windings are formed by a cylindrical former and hung on core limbs, as illustrated in the above figure. The cylindrical coils come in distinct layers, and each is separated from the other. Materials like cloth, paper or mica are a good choice to create insulation. Windings that are low voltage are positioned closer to the center, since they are more easy to insulate.
(Ii) Shell Type Transformer
The coils are wrapped and placed in layers that are stacked, with insulation in between. Shell type transformers may be a simple rectangular shape (as as shown in the above illustration) or be a distributed shape.
(B) Based on the nature of their intended purpose
- The step-up transformer is a device that rises (with an inverse decrease in current) at the secondary.
- Step down transformer The voltage decreases (with an growth of current) at the secondary.
(C) Based on the nature of supply type
- Single phase transformer
- Three phase transformer
(D) Based on an assumption of usage
- Power transformer: It is used in the transmission network High rating
- Distribution transformer is used in distribution networks typically have a lower rating than power transformers.
- Instrument transformer: Used for relay and protection functions for various industrial instruments
- (CT) Current Transformer (CT)
- Potential transformer (PT)
(E) Based on the principle of cooling used
- Self-cooling type with oil.
- Type of water-cooled type that is oil-filled
- Air blast type (air cooled)