Transformers are used in various fields such as power generation grid, distribution sector, transmission and electrical energy consumption.There are different types of transformers which are classified on the basis of following factors;
Based on Phase
According to the supply used, transformers are mainly classified as single phase and three phase transformers.
- A typical transformer is a single phase transformer. It consists of primary and secondary winding and is operated to increase or decrease the secondary voltage.
- A three phase transformer is a transformer in which three primary windings are connected together and three secondary windings are connected together.
A single three phase transformer is preferred over three single phase transformers to achieve good efficiency, where it occupies less space at a lower cost. But due to the problem of transportation of heavy equipment, single phase transformer is used in most of the cases.
Another classification of these transformers is core and shell type;
- In the shell type, the windings are located on a single leg surrounded by the core.
- In the Core type, they are tied on separate legs.
Based on Voltage Levels
Commonly used transformer types, on the basis of voltage they are classified as:
- Step-up Transformer: These are used between the power generator and the power grid. The secondary output voltage is greater than the input voltage.
- Step Down Transformer: These transformers are used to convert high voltage primary supply into low voltage secondary output.
Related Tutorial: What is Transformer? Step-up and Step-down Transformer?
Based on the medium of core used
Different types of cores are used in a transformer:
Air core Transformer
It is a core type transformer consisting of windings mounted on a non-magnetic stripe. Magnetic flux connections are created between the primary and secondary as the air moves through the core.
These air core transformers have low hysteresis and eddy current loss and noise output is low.
Air core transformer has high reluctance and The reciprocal inductance in air core is less as compared to iron-core transformer. It is used in Audio frequency and High frequency radio Systems.
Iron Core Transformer
It is a core type transformer in which the winding is wound on an iron core. The magnetic flux linkage is made strong and perfect with iron as the main material. This is commonly seen in laboratories.
They have very high magnetic permeability. Iron core transformers have low reluctance. The mutual inductance is high and highly efficient.
These are slightly noisier than air core transformers. The hysteresis and eddy current loss is slightly higher than in air core transformers. it is used as isolation transformer and high frequency radio transmission.
Transformers are also classified according to the type of core they use. Some transformers use a core immersed in oil. This oil is cooled from outside in various ways. Such transformers are named as wet core transformers, while others such as ferrite core transformers, laminated core transformers, toroidal core transformers and cast resin transformers are dry core transformers.
Transformers can also be classified on the basis of the type of main material used.These are actually RF transformers, which include many types of air-core transformers, ferrite core transformers, transmission line transformers and balloon transformers. Balloon transformers are used in RF receiver systems. The main types are air core and iron core transformers.
Based on the winding arrangement
Auto Transformer
This is a type of transformer mostly seen in our electrical laboratories. This auto transformer is an improved version of the original transformer. A single winding is taken to which both sides are connected to power and ground. Another variable is tapped whose movement forms the secondary of the transformer.
A single winding provides both the primary and the secondary in the transformer. Various tappings of the secondary winding are designed to select different voltage levels on the secondary side.
The primary winding is from A to C and the secondary winding is from B to C while the variable arm B is varied to obtain the required voltage level.
By rotating the shaft above, the secondary voltage is adjusted to different voltage levels. If the voltage applied at points A and C is V1, then the voltage per turn in this winding will be
Now, the voltage between point B and C will be
This constant is nothing but the turn ratio or voltage ratio of the auto transformer.
Based on Install Locatio
Power Transformer
It is used at power generation stations as they are suitable for high voltage application.
A power transformer is a stationary device used to convert power from one circuit to another without changing the frequency. This is a very simple definition of a transformer. Because there is no moving or rotating component, a transformer is modeled as a stationary device. Power transformers perform based on AC supply. A transformer works on the laws of mutual induction.
Power transformers can be divided into three types according to categories. They are large power transformers, medium power transformers and small power transformers.
- Large power transformers can have a range of 100MVA and beyond.
- Medium power transformer can be in the range of 100MVA.
- Low power transformers can be in the range of 500-7500kVA.
Distribution Transformer
Mostly used in the distribution lane for domestic purposes. They are designed to carry low voltage. It is very easy to install and is characterized by low magnetic loss.
Distribution transformers work for circulation purposes. Therefore, such equipment will bring down (step down) the voltage and contingency level of the power transmission line to a predetermined scale. This predefined level is also known as end user protection level for domestic consumers or for industrial purposes.
There are different types of transformers available like single phase, 3-phase, underground, pad-mounted, pole-mounted transformers.
Measurement Transformers
These are further classified. They are mainly used to measure voltage, current, power.
Measuring transformer means either a current transformer (“CT”) or voltage transformer (“VT”) or an instrument carrying such functions as is intended to enable metering equipment to operate at more convenient currents and/or voltages .
Protection Transformers
They are used for component protection purposes. In the circuit, some components must be protected from voltage fluctuations etc. Safety transformer components ensure safety.
