Working principle of transformer|electricaltechguru

Working principle of transformer

What is transformer?

Transformer is a static device,which is transform electric power from one circuit to another circuit without changing in frequency.

Transformer can step up and step down the voltage corresponding to step down and step up the current respectively. Transformer work on the basis of mutual induction principle between to circuit which links with the common magnetic field.

Transformer core is made up of low reluctance material that is silicon steel and the winding of transformer is highly inductive.
 Transformer having Two electrical circuits link with common magnetic circuit. One is primary circuit and another is secondary circuit. When primary energizing with AC supply alternating flux produce which flow through magnetic path and links with secondary winding due to mutual induction. And the EMF induced in secondary winding according to Faraday law of electromagnetic induction. Open the secondary winding having a closed path current flow through this secondary winding.

Construction of transformer:

Transformer consists of two inductive coils links with common magnetic path that inductor coils namely primary coils and secondary coil.

Transformer core, winding view

 Core of the transformer is made up of steel material and that acts as a magnetic path of the flux. Core of the transformer made from number of silicon steel stampings laminated are comes together. Material of transformer core made up of low reluctance, high permeable material. To minimise the eddy current loss core made up of number of laminated steel stamping. Thickness of that steel stamping about 0.30mm for 50 Hertz.
On the basis of construction transformer divided into two different types core type and shell type.

 types of transformer on construction basis

1. Core type
2. Shell type
3. Berry type

Core type transformer

As shown in figure core type transformer having two windings that is primary winding and secondary winding which links with each other by magnetic path that is core. Coils used in transformer its cylindrical, circular, rectangular type can be used.
In small size core transformer rectangular shape of core used, in large core transformer cylindrical or rectangular type of core is used. Also stepped core can be used, per stepped core circular or cylindrical type of winding is used. Core stepping gives high space factor. Stepped core is one of the most commonly used for large type of core transformer due to that stepped core I2R loss also reduced. In large power transformer more number of stepped can be used.

Shell type transformer

In this type of transformer multilayer disc type winding mounted on the same limbs of transformer core which are insulated from each other and also the core of the transformer.
In this type of transformer most commonly used transformer is berry type of transformer. This type of transformer having some advantages over core type.

• More rigid construction
• Lesser weight and size per KVA is small
• Lower iron losses at higher flux density
• Lower manufacturing cost


Large size of transformer fully airtight chamber is used for tank in which insulating oil field which work as insulating medium between winding to winding and winding 2 to outer body of transformer, this will also act as a coolant of the transformer which circulate through to the plates that is cooling plates of the transformer.
On supply basis transformer is single phase transformer and three phase transformer
On the basis of voltage conversion there is step up transformer and step down transformer.

Related post:Three phase induction motor

Transformer body part

Transformer body parts

1.Core

 material of core is highly permeable which is made from silicon steel. The core of transformer is made up from number of stamping which are laminated by insulating material like varnish, that’s stampings are laminated and width of that stampings is 0.35mm for 50 hertz frequency. Number of stampings attacks each other and the core transformer
Core is divided in number of stamping because of reducing eddy current losses because in solid material eddy current losses more so, hitting is more and that's why losses that is iron loss is more. Enlarge size of transformer more. For large size of power transformer stepped core is used.
In transformer iron loss is called as constant loss.

2.Winding:

 winding of the transformer is  of high conductive material that is copper, aluminium is used. This winding is different in safe for such as small power transformer having rectangular type coil is used. For large power transformer circular or rectangular type of.
The winding of the transformer we can say primary winding and secondary winding. If the transformer is step down transformer then the turns of the primary winding is greater than secondary winding and if the transformer is step up transformer then the turns of the primary winding less then turns of secondary winding. So, the number of turns in primary winding and secondary winding will decide the types of transformer that is step up transformer or step down transformer

3.Breather:

See the above picture for breather

Breather is located at the conservator tank, by the pipe arrangement
Breather have mainly two works are there sucking air inside the tank and exhaust air to the atmosphere when will temperature decreases and increases, and II work of the brother is is to remove the moisture from the air which will entering in transformer tank at the time of sucking air from the atmosphere.
Breather consists of silica gel which is bluish in colour colour at the time of fresh condition and after absorption of moisture by aging affect its will pink in colour. the colour of the silica gel will decide the condition of silica gel. When it's become pink in colour its have to be replaced with new one.

In airtight transformer tank, breather is necessary. When the transformer oil is heated size of the transformer oil expanded due to expanding properties of molecule and it's require more space at the time of expanding oil air inside the tank is exhaust in atmosphere.
When the temperature of transformer oil decreases its previous state state so with this space required to the oil is also decreases. At that time breathing is necessary and atmosphere air inside the tank the tank of the transformer.

4.Explosion vent:

Explosion vent is a protective device used for transformer protection from the internal fault.
at the time of internal fault of the transformer gases inside the transformer tank increases suddenly that that gases have to be exhausted in the atmosphere quickly otherwise the tank of the transformer will damage, to avoiding this damage explosion vent is used to exhaust gases quickly.

 5.Transformerr oil:

Transformer oil is used for mainly two purposes first is cooling and second one is to provide insulation between winding to winding and winding to body of the transformer.
Transformer oil has good insulation property, power transformer strength of the transformer oil has to be check for every 6 month to avoid any damage.

6.Buchholz relay:

Buchholz relay is placed between the transformer tank and conservative tank.
Buchholz relay is a protective device use for the transformer protection from internal faults. When the internel faults occur in transformer, number of gases produced inside the type of transformer hydrogen nitrogen etc.
When the internal faults occur in transformer winding number of gases are produced that gases force the float of the buchholz relay proper sites that's why the alarm and tripping command send to the breaker of the transformer.

 7.Conservator tank:

Conservator tank is used at the top of the transformer tank. It is used for the storage of oil.
When the temperature of transformer oil increases it is expanded and it needs some space and that space provided by the conservator tank

8.Bushing:

Transformer has two windings HV winding and LV winding. HV winding connected to HV bushing and LV winding connected to LV bushing. The electrical connection of the transformer is given through that l b and HV bushing. Depending on the type of transformer that is step up or step down that is decided  the incoming supply of the transformer and the outgoing supply of the transformer connected to which winding.
In step up transformer primary winding is connected to low voltage side and secondary winding connected to high voltage side. In step down transformer primary winding connected to high voltage side and secondary winding connected to low voltage side.

Related post:Single phase inducton motor

9.cooling plates

Cooling plates are basicaly work as heat exchanger,which are exchanged heat of transformer oil and atmosphere air.oil cooling is done by using atmosphere air.