Types of Transformer -
Technical features and applications.

  1. Transformers.
  2. Types of transformers.

1 - Transformers:

Types of transformer and their functions and features.

Transformer is a static and electrical device. It is used for transferring the voltage from one coil to another coil at different voltage as on same frequency. It works on mutual inductance process. High voltage and low current changes into low voltage and high current. Low voltage and high current changes into high voltage and low current as on same frequency.two coils-primary and secondary are used separately but both are installed on same insulated iron core.

When primary winding is charged with primary voltage this voltage may be high or low according faraday law the back emf is generated into primary winding resultant magnetic flux will be produce and it will be transferred into secondary winding. Secondary winding will generate voltage as per coil turns.

2 - Type of voltage transformation:

1 - Step Up

Step up is a types of a transformer which is used for voltage transformation as low voltage to high voltage just like as 11 KV into 33 KV, 33 KV into 66 KV, 66 KV into 132 KV, 132 into 220 KV and 220 KV into 400KV.
It has two winding, primary and secondary. Low voltage is received in primary side and high voltage is generated in secondary side. High voltage is used in power transmission because when voltage increasing then current will be decrease.


Step up transformer is mostly used in transmission system which is used for sending the electricity at one place to long distance place.

2 - Step down

Step down is a types of a transformer which is used for voltage transformation as high voltage into low voltage just like as 220 KV into 132 KV, 132 KV into 66 KV, 66 KV into 33 KV and 33 into 11 KV.
It has two winding, primary and secondary. High voltage is received in primary side and low voltage is generated in secondary side. Medium voltage(33KV, 11KV) is used for power distribution in sub station so after receiving high voltage as 220 KV, 132 KV, 66 KV from transmission line then voltage is transformed in step down as 220 KV into 132 KV, 132 KV into 66 KV, 66 KV into 33 KV.


Step down transformer is mostly used in transmission system which is used for receiving the electricity from transmission line.

3 - Type of cooling:

1 - Oil type

A insulated oil is the medium of cooling in transformer and this type transformer is called as oil type transformer. Primary and secondary winding of transformer are put into oil tank


Oil type transformer are used above 500 KVA. It is low cost high efficiency transformer and used in sub station and industries.

2 - Dry type

Dry type transformer is a low maintenance cost and high initial cost static device. It is also safe from fire and it can be installed in side premises as basement. It is constructed with cast resin type windings.
A temp protection relay is used for monitoring temp and it has also four functions. After crossing temp set limit, a tripping signal is sent to the breaker shunt coil and hooter also for announcing.


Dry type transformers are used in distribution system like as industries, high rise building etc.

4 - Type of phase:

1 - Single phase

Single phase transformer is used in utilization equipments for 220 Volt AC into 12 Volt DC


TV and electronic devices etc.

2 - three phase

Three phase transformer is a electrical static device which is used for voltage transformation like as step up and step down transformer.


Three phase transformer are used in generation, transmission and distribution of electrical system.

5 - Arrangement of coil:

1 - Cylindrical type

Cylindrical type windings are used in three phase windings. It is low voltage type windings as 6.6 KV to 750 KVA. In side primary winding are used and outside is secondary windings is used.

2 - Disk type

The disk type windings are used for high capacity ratings transformers. These windings are connected in numerics flat coils in parallel or series. The conductor of coil are used as flat strip which is constructed in radical direction. the size of conductor may be 4 to 50 sq.mm.


Disk type transformer are used in high voltage applications.

6 - Type of applications:

1 - power transformer

Power transformer is high voltage transformer static device which is used in transmission line as 220 KV to 33 KV for step up and step down functions. It is the high power transformer.


It is used in transmission line as step up and step down transformer.

2 - Distribution transformer

Distribution transformers are static electrical device which is used for supplying the power supply in domestic and industries. It is used in sub station for power distribution as 33 KV and 11 KV. These HT 33 and 11 KV voltage is converted into 440 voltage through stepdown distribution transformer.


Residential areas, Residential societies and industries.

3 - Instrument transformer

Instrument transformer is a measuring electrical device like as CT and PT. CT is connected in series and is used for measuring load current. PT is connected as parallel in electrical system and is used for measuring voltage.


CT is used in utilization, distribution and transmission system but PT is used in HT system where the voltage is high like as 11KV, 33KV.

7 - Type of core:

1 - core type

Transformer are designed in different types lik as core type, shell type and berry type. Here we are going to discussing about core type design. Single phase has 2 winding core so winding is surrounded on limb. Tree phase has 3 windings so core limb is three and windings are surrounded on limb.

Shell type transformer is designed on the two limbs which is used for primary and secondary as separately. The mostly are is covered by windings which surrounds area of core. The core shape is L type.

2 - Shell type

Shell type transformers are designed as three vertical limb and two horizontal section. Windings are put on the central limb and other is used for magnetic flux. The nature cooling is not effective properly because winding is fixed on central limb.

3 - Berry type

In really Berry type transformer is a similar as shell type which name is given by designer. The similar difference is windings as cylindrical shape and independently magnetic circuits is more quantity like as spokes in a wheel.


It is used in high capacity transformer which is best for temp reducing.

8 - Type of windings:

1 - Two winding ordinary type

Each phase has two windings like as primary and secondary. both are separately each other and primary is used for input supply and secondary is used fro output supply. Both windings are connected with magnetic core. When power supply is received in primary then magnetic flux is produced and transfer into secondary winding. Resultant the output power supply is received form secondary windings.

2 - Single winding auto type

Auto transformer is designed totally different in comparison of normal transformer. Only one windings are used in each phase which is divided into two parts as primary and secondary. In this winding three taping is available, two is fixed and one is variable so that we could increase or decrease voltage. It works as stabilizer function.

9 - Type of winding connections:

1 - Delta-delta connections:

Four type connection are used in three phase transformer as delta-delta, delta-star, star-delta and star-star. Firstly we are going to discuss about delta-delta winding connection in three phase transformer. Two nos windings, one is primary and 2nd is secondary.
Both is connected in single phase and three phase. Single phase has one primary and one secondary but three phase has three nos primary and three nos secondary as each phase R, Y and B.

2 - Delta-star connections

The ∆-Y connection is used in distribution of power for utilization as 11KV into 415 Volt. It is known as another name as three phase four wire system because neutral is received from output star winding.

3 - Star-star

The stage current is equivalent to the line current, and they are in stage. The line voltage is multiple times the stage voltage. There is a stage partition of 30º between the line and stage voltage.The 180º stage shift between the essential and optional of the transformer is displayed in the figure above.

3 - Star-delta

The star-delta association of three stage transformer is displayed in the figure above. The essential line voltage is √3 times the essential stage voltage. The optional line voltage is equivalent to the auxiliary stage voltage. The voltage proportion of each stage is line-to-line voltage ratio of Y-∆ connection.

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