A transformer is the most important machine of an electric power system as it is used to transfer electrical energy from one circuit to another changing voltage and current level keeping frequency and power constant. Due to the use of transformer in electric power system, it is possible to transfer electrical energy for longer distance efficiently with minimum losses. So we must need to know about the all different parts of transformer in detail that helps to make this possible.
Different Parts of transformer
The various parts of transformer has been listed below.
- Main Tank
- Bushings and Terminals
- Tap Changer
- Conservator tank
- Silica-gel Breather
- Explosion Vent
- Buchholz Relay
- Radiators and Cooling Fans
- Transformer Oil
- Laminated core
- Winding
- Insulating Materials
Some of the parts like main tank, bushing and terminals, winding, laminated core e.t.c. are general parts of the transformer i.e found in every transformer but the parts like tap changer, explosion vent, radiators and cooling fans e.t.c are found mostly in larger transformer.
Explanation of Different Parts
One by one detailed explanation of all different parts of transformer are given below.
1) Main Tank
The main tank is the part of power transformer which is made up of fabricated rolled steel plates and filled with transformer oil and the winding and laminated core is immersed in the oil. They are provided with lifting hooks and cooling tubes. Sometimes aluminium sheets are also used instead of steel plates to reduce weight and stray losses. Nowadays, aluminium tanks are more familiar than steel tank due to lighter weight but costly.
The main tank is made of serpentine sheets instead of straight sheets to make the cooling system more efficient for large capacity power transformers because the use of serpentine sheets reduces the surface area of the tank, the heat is emitted faster and the power transformer stays cool.
The purpose of main tank has been listed below.
- It protects core and winding from external aspects.
- It is the container for the transformer oil.
- It supports all other components of the transformer.
2) Bushings and Terminals
Terminals are mounted upon the bushing and connected to the winding ends for connecting the incoming and outgoing cables of the loads and supplies.
Bushings are insulators mounted over the main tank that is used to form barrier between terminals and main tank. They are made up of porcelain and epoxy resins. Bushings provide safe passage for the conductors connecting terminals to the winding. As winding there are two types of the bushings on the basis of voltage which are listed below.
- Low-voltage Bushing
- High-voltage Bushing
3) Tap Changer
The main function of the tap changer is to regulate the output voltage by changing its turns ratio(i.e alternating the number of turns). Automatic tap changer are also available. There are two types of tap changer which are listed below.
- On-load tap changer (without isolation)
- Off-load tap changer (Need to isolate)
4) Conservator Tank
Conservator tank is a airtight metallic cylindrical tank mounted on the top of the supporting structure of the transformer. Conservator tank is vented at the top above the main tank and bushings and generally half-filled with the transformer oil to allow expansion and contraction due to change in temperature of the winding.
The main function of the conservator is to provide the extra space for the expansion and contraction of the transformer oil due to variation in the temperature of the winding. It is connected to the main tank through a pipe on which buchholz relay is mounted. A level indicator is also installed on it to measure the quantity of oil inside the conservator tank.
5) Silica-gel Breather
Silica-Gel Breather is a cylindrical container filled with silica-gel to keep air entering in-to the transformer moisture free. It is present in the oil immersed transformer that have conservator tank. Silica-gel Breather is directly connected with the conservator tank. Silica-gel Breather is attached to the end of the air pipe of conservator such that air enters and exits the conservator through the breather.
The main function of the silica-gel breather is to supply moisture-free dry fresh air to the conservator tank during the expansion and contraction of transformer oil due to variation in temperature of the transformer oil. This is because the transformer oil when reacting with moisture can damage the insulation and cause any internal fault. That’s why the air entering in conservator tank must be moisture free for longer life of transformer oil and better performance.
In a breather, when air passes through silica-gel then, the moisture present in the air is absorbed by the silica-gel crystals. Hence, moisture-free dry fresh air enters into the transformer through the conservator tank. Thus we can also say “breather is acting as an air filter for the transformer”.
6) Explosion Vent
Explosion vent is a metallic pipe with a diaphragm at one end. It is an important parts of the transformer. It is installed on the main tank and its level is normally mentioned above the level of the conservator tank. It is only installed in high rated power transformer.
The main function of the explosion vent is to expel the hot boiling oil from transformer to atmosphere in-order to avoid explosion during excessive pressure build up in the main tank due to heavy internal faults. It acts as an emergency exit for hot boiling oil and hot air gases present inside the main tank during heavy internal faults.
The explosion vent works as same as the safety valve works in the pressure cooker. Hence, in other words we can also called “the explosion vent is the safety valve in case of the transformer”.
7) Buchholz Relay
Buchholz relay is a gas-actuated relay mounted on the pipe connecting the main tank and conservator tank. It operates due to the emission of gases due to decomposition of insulating oil due to heat produced during internal faults. It is most important parts of oil-immersed transformer of power rated over 500KVA.
The function of the Buchholz relay is to protect the transformer from all kinds internal faults such as short circuit fault, inter-turn fault etc. It protects protects the transformer from all kinds of internal faults that produces heat including minor faults.
When short circuit occurred in the winding then it generates enough heat that decompose the oil into gases ( like hydrogen, carbon monoxide, methane, etc). These gases move towards the conservator tank through the connecting pipe which activates the Buchholz relay. Then, Buchholz relay sends signal to trip and alarm circuits to activate alarm and circuit breaker. Then the circuit breaker disconnects the transformer from the supply.
8)Radiators and Cooling Fans
Since over-heating causes power losses, a cooling arrangement is required for the power transformer. Dry-type transformers are generally natural air-cooled. But when we talk about oil-immersed transformers then several cooling methods are used depending upon power rating, losses and level of cooling required.
Radiators and cooling fans are installed on the main tank to cool of the insulating oil. Radiators are also called cooling tubes.
The main function of cooling tubes or radiators is to transfer heat generated by core and winding to the environment by circulating heated hot oil throughout the cooling tubes either by naturally or forced.
In natural cooling system, when the temperature of the oil rises hot oil naturally rises to top and cold oil sinks to downward. Thus oil naturally circulates through the radiators and cools the core and winding.
In forced cooling system, a cooling fans is fitted on the radiator to force the hot oil to circulate through the radiators also air is forced for proper cooling.
9) Transformer oil
The function of transformer oil is to provide insulation between the winding and works as coolant. It can be used as coolant because of its chemical properties and very high dielectric strength.
It dissipates the heat generated by the core and winding to the external environment. When the winding or core gets heated due any fault, the oil cools down the winding or core by circulating the oil through the radiators or cooling tubes by transferring heat to the atmosphere.
Hydro-carbon mineral oil is used as transformer oil that acts as coolant. It is composed of aromatics, paraffin, naphthenes, and olefins.
10) Laminated core
Laminated core is one of the most important parts of transformer which is used to support the winding of the transformer. It is made up of laminated soft iron material to reduce eddy current loss and hysteresis loss. Laminated core also provides a low reluctance path to flow the magnetic flux.
The diameter of transformer core becomes directly proportional to copper losses and inversely proportional to iron losses or core losses.
There are two types of the core according to construction which are listed below.
- Core type
- shell type
11) winding
In a transformer, there is always two sets of winding (primary and secondary) placed on laminated core insulated from each other and laminated core. Winding is separated using insulated sheets. The primary winding is connected to the supply and the secondary winding is connected to the load.
Winding consists of several number of turns of copper conductors formed in a coil that is bundled together.The arrangement of winding depends upon the current rating, short circuit strength, temperature, impedance and surge voltage.
The main function of winding is to produce magnetic flux in primary winding and induce mutual EMF in secondary winding for the operation of transformer.
Based on the voltage level of supply, winding are further classified into two types which are listed below.
- High voltage (HV) winding
- Low voltage (LV) winding
12) Insulating Materials
Insulating materials are one of the most important part of transformer. Insulation failure can cause heavy damages to the transformer. So, used insulating material must be of high grade. Insulation is required between each turn of winding, between winding and core and also between all current-carrying parts and main tank.
The main function of insulating material is to isolate the winding from each-other and core. It also isolate all the current carrying parts and main tank. It is used to avoid the short circuits.
Insulating materials must have high dielectric strength, good mechanical strength and temperature withstand capability.
Insulating materials like papers, cloth and card boards are used to isolate primary and secondary winding from each-other as well as from the core.
Conclusion
Hope, you have clearly understand about the different parts of the transformer, Its name, function in transformer, location, uses etc. Make sure to leave your opinion and suggestion about this post in the comment section below.