Transformer
is a static electromagnetic device used for transforming a given AC voltage into desire output AC voltage at same frequency. The designed characteristics of transformer enable us to utilize it for different purpose in generation, transmission, distribution and utilization. In this article, we will discuss different types of transformers based on their classification.
Classification based on Voltage Levels:
Depending on the voltage level, transformer is classified as step up and step down transformers.
Step Up Transformer:
Transformer which increases the voltage level is known as step up transformer. In step up transformer, induce voltage across the secondary coil is greater than the applied primary voltage. Moreover, number of secondary winding turns are more in step up transformers as compared to the number of primary turns .
Step Down Transformer:
Transformer which decreases the voltage level is known as step down transformer. Induce voltage across the secondary coil is less than the applied primary voltage in these type of transformers. Hence number of secondary turns are also less as compare to the number of primary winding turns in step down transformers.
Classification based on Construction:
According to the construction, there are two types of transformers which are termed as:
Core Type Transformer:
In core type transformer, magnetic core of transformer is made up of simple rectangular laminated piece of steel. Rectangular core is used with cylindrical coils which are either circular or rectangular. Primary and secondary windings wound outside surrounds the laminated core. Both windings are wrapped around each of the limb. These types of transformers are generally used in high voltage applications like in auto, distribution and power transformers.
Shell Type Transformer:
Shell type transformer consist of three-legged laminated core in which both primary and secondary windings are wrapped around the center leg. In shell type, windings are surrounded by the laminated core. These types of transformers are mostly used in low voltage applications like in electronic circuits. In both types of transformer, core is constructed of thin laminations in order to reduce eddy current losses .
Classification based on Supply:
Single Phase Transformer:
Single phase transformer is connected with one phase primary voltage and transforms the given voltage into one phase secondary voltage. They are mostly used in household device applications. Single phase transformer consist of two windings, one on the primary and the other one is at the secondary side.
Three Phase Transformer:
Three phase transformers are connected with three phase system. It transforms three-phase primary voltage into three phase secondary voltage. They are generally used in transmission and distribution. In three-phase transformer, there will be three windings for each primary and secondary side(can be seen in the fig). Individual windings are either connected in star or delta configuration depending on the system requirements.
Classification based on Usage;
Distribution Transformer:
Distribution transformers are generally used between local substation and consumers. They are always used in low voltage levels for connecting end users among (11kv, 3.3kv,440v,230v). Distribution transformer doesn’t operate at full load all the time since its load depend on the distribution demand. Due to unknown distribution of load, these transformers are designed to have maximum efficiency occurs at 60 % to 70% of the rated load. They are generally rated less than 200 MVA.
Power Transformer:
Power transformers are used in transmission and generating stations at high voltages. They are basically used in step up and step-down applications (400kv,200 kv,110kv,33kv) for transmission and receiving purpose. Power transformers are used at the generating end and has to transfer whole power that is being generated. Hence they are designed in such a way to give maximum efficiency at rated 100% load. These transformers are generally rated above 200 MVA.
For Full detail, kindly read the following article:
Difference between Power Transformer and Distribution Transformer 
Classification based on Instruments:
Instrument transformers are special type of transformers used to step down the high voltages and currents for the purpose of measurement and protection. Potential (voltage) transformer and current transformer are two types of instrument transformers.
Current Transformer:
Current transformer is used to step down the large currents to low values for the purpose of measurement and protection. They step down the heavy current to such lower values which are suitable for operation of relays and other measuring instruments connected with their secondary winding.
For Full detail of Current Transformer, Kindly read the following article:
What is Current Transformer ? Construction & Types
Potential Transformer:
Potential transformer is a voltage step down transformer used to reduce high voltage to lower value for the purpose of measurement and protection. It also provide isolation between high voltage network and measuring instruments connected to its secondary. Potential transformers are connected in parallel to the line which is to be monitored for protection.
That’s all. Hope this will helps you.
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