Definition of Transformer
Electrical Power Transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two winding's.It transforms power from one circuit to another without changing its frequency but in different voltage level.
Mutual Induction between two or more winding is responsible for transformation action in an electrical transformer.
The three main parts of a transformer are,
- Primary Winding of transformer - which produces magnetic flux when it is connected to electrical source.
- Magnetic Core of transformer - the magnetic flux produced by the primary winding, that will pass through this low reluctance path linked with secondary winding and create a closed magnetic circuit.
- Secondary Winding of transformer - the flux, produced by primary winding, passes through the core, will link with the secondary winding. This winding also wounds on the same core and gives the desired output of the transformer.
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Types of Transformer
Transformers can be categorized in different ways, depending upon their purpose, use, construction etc. The types of transformer are as follows,- Step Up Transformer & Step Down Transformer - Generally used for stepping up and down the voltage level of power in transmission and distribution power system network.
- Three Phase Transformer & Single Phase Transformer - Former is generally used in three phase power system as it is cost effective than later. But when size matters, it is preferable to use a bank of three single phase transformer as it is easier to transport than one single three phase transformer unit.
- Electrical Power Transformer, Distribution Transformer & Instrument Transformer Power transformers are generally used in transmission network for stepping up or down the voltage level. It operates mainly during high or peak loads and has maximum efficiency at or near full load. Distribution transformer steps down the voltage for distribution purpose to domestic or commercial users. It has good voltage regulation and operates 24 hrs a day with maximum efficiency at 50% of full load. Instrument transformers include C.T & P.T which are used to reduce high voltages and current to lesser values which can be measured by conventional instruments.
- Two Winding Transformer & Auto Transformer - Former is generally used where ratio between high voltage and low voltage is greater than 2. It is cost effective to use later where the ratio between high voltage and low voltage is less than 2.
- Outdoor Transformer & Indoor Transformer - Transformers that are designed for installing at outdoor are outdoor transformers and transformers designed for installing at indoor are indoor transformers.
- Oil Cooled & Dry Type Transformer - In oil cooled transformer the cooling medium is transformer oil whereas the dry type transformer is air cooled.
- Core type, Shell type & Berry type transformer - In core type transformer it has two vertical legs or limbs with two horizontal sections named yoke. Core is rectangular in shape with a common magnetic circuit. Cylindrical coils (HV & LV) are placed on both the limbs. Shell type transformer: It has a central limb and two outer limbs. Both HV, LV coils are placed on the central limb. Double magnetic circuit is present. Berry type transformer: The core looks like spokes of wheels. Tightly fitted metal sheet tanks are used for housing this type of transformer with transformer oil filled inside.
- Furnace type Transformer: Furnace transformers are inside hot furnaces. This close proximity to incredibly high temperatures, particularly in industrial applications, means that the function and construction of furnace transformers is quite different from standard circuit transformers working in cooler environments. As such, many furnace transformers come equipped with an automatic cooling mechanism and many use multiple outlets in order to support loads of various sizes. These specialized needs make industrial furnace transformers more expensive than other types of industrial transformers.
Auto Transformer: A kind of electrical Transformer where primary and secondary shares same common single winding. So basically it’s a one winding transformer.
Distribution Transformer:
The step down transformers used for electric power distribution purpose are referred as distribution transformer. There are several types of transformer used in the distribution system. Such as single phase transformer, three phase transformer, pole mounted transformer, pad mounted transformer and underground transformer.
Distribution transformers are generally small in size and filled with insulating oil. These transformers are available in the market in various sizes & efficiency. Selection of distribution transformer depends upon the purpose and budget of the end users.Secondary terminals of distribution transformer deliver electrical power at a utilization voltage level to the consumer end via energy metering system.
In case of three phase distribution system three phase four wire secondary systems are adopted. Here, three phases, which means red, yellow and blue phase conductors, come out from three low voltage bushing studs of the transformer. The neutral wire is connected to the fourth bushing which is also referred as a neutral bushing of the transformer.- Generator Step-up Transformer: (GSU) are the critical link between the power station and the transmission network, often operated day and night at full load. They must be built to withstand extreme thermal loading without ageing prematurely.
These transformers are located in a power station and are built as single-phase or three-phase unit's. GSU take the voltage from the generator voltage level up to the suitable transmission voltage level.
