Transformers are essential electrical devices used to transfer electrical energy between circuits at different voltage levels. Whether it's a power station, substation, or industrial plant, transformers play a crucial role in voltage regulation and energy distribution.
To understand how a transformer works, it's important to learn about its internal structure. In this article, we’ll explore the key components of a transformer such as the core, windings, conservator, breather, bushings, and more—along with their functions and importance in real-world applications.
This guide is especially useful for students, electrical engineers, and aspirants of competitive exams like SSC JE, RRB JE, GATE, UPPCL JE, and more.
A Transformer consists of following parts:
- Main tank
- Core
- Windings
- Conservator tank
- Breather
- Pressure relief pipe
- Buchholz relay
- Bushings
- Tap Changer
- Radiator
- Header & Footer of the radiator
- Cooling fans
- WTI & OTI (Winding Temperature Indicator & Oil Temperature Indicator)
Main Tank
- It is the main part of the transformer which made of a steel box. The transformer core placed inside the main take.
- It filled with insulating oil. Its shape is like a cube or, cylindrical that depends on construction.
Core
- It consists of laminated silicon steel sheet for all type of transformers to provide a continuous magnetic path and also to provide the minimum air gap.
- By making core laminated eddy current losses also reduced in the core. Laminations of the core also insulated from each other.
Windings
- In case of single phase transformer, it has one primary winding and one secondary winding, while in case of three phase transformer it has three primary winding and three secondary winding. It also is known as low voltage winding and high voltage winding that’s depend on which type of transformer, step up or step down.
- Low voltage winding is always placed the inner side of the core and High voltage winding is placed above the low voltage winding. Both windings are electrically insulated from each other through the insulation material. There is also a proper distance between two windings for movement of oil.
- Both the winding can connect in star or delta with proper phase shift in case of the three-phase transformer.
🔍 Why Low Voltage (LV) Winding is Placed Closer to the Transformer Core than High Voltage (HV) Winding?
✅ 1. Insulation Requirement
- The low voltage winding is placed closer to the core because it requires less insulation between the winding and the core.
- The high voltage winding, being at a higher potential, needs thicker insulation from the core and other parts.
- Placing HV winding outside the LV winding provides enough space to accommodate this insulation safely and economically.
✅ 2. Cost Optimization
- Insulating high voltage winding from the grounded core would be very costly if placed near the core.
- So, by placing the LV winding inside, we reduce the insulation cost significantly.
✅ 3. Better Cooling and Heat Dissipation
- LV winding is generally of thicker conductors due to higher current and is placed inside to allow better contact with the core, which helps in heat dissipation.
✅ 4. Mechanical Strength
- During short-circuit conditions, the winding must withstand strong mechanical forces.
- Placing LV winding inside ensures better mechanical support due to its proximity to the rigid core.
Conservator Tank
- This is cylindrical tank which is mounting on the roof of a transformer. The main function of conservator tank provides adequate space for insulating oil during expansion.
- When the temperature of the transformer is increased due to any reason than the volume of transformer oil also increased then that condition conservator tank provides adequate space for transformer oil for expansion and act as the reservoir.
Breather
- Breather is a device which used for Breathing of transformer. When the transformer is loaded then the temperature of transformer increased and the temperature of insulating oil also increased consequently the volume of insulating oil increased.
- As the volume of transformer oil increased then the air above the oil level in conservator tank out from the breather. When the temperature of insulating oil decreased than that case the volume of insulating oil also decreased which case air to enter into conservator tank.
Breather of Transformer
Pressure relief Pipe
- It provides protection to transformer from high pressure. Sometimes the high pressure is developed inside a transformer due to decomposition of oil.
Buchholz relay
- It is protection device which is used in the transformer. It is connected between main tanks to conservator tank through a pipe. It is used to sense the internal fault of the transformer.
Buchholz Relay
Bushings
- Bushings are used to bring the windings out of the tank and also use for insulation.
Bushing of Transformer
Tap Changer
- The secondary voltage of transformer depends upon the primary voltage and the load.
- When the transformer is in loaded condition then the voltage on the secondary terminal decreased and when the transformer is unloaded condition then the voltage on secondary terminal increased. To overcome from the voltage variation tap changer are used.
Radiator
- The radiator is used to increases the surface area for dissipating heat of the oil.
- When the transformer is under loaded condition, then the current flowing through windings. By flowing of electric current, heat is produced in the windings, the heat produced in winding cause rises of the temperature of the insulating oil.
- The rating of the electrical machine depends upon the maximum permissible temperature rise limit. The radiator of the transformer is used to accelerates the rate of cooling of the transformer. Thus, the radiator plays a great role in increased loading capability.
Radiator of Transformer
Header & Footer of the Radiator
- The header is connected between main tank and radiator at upper side and footer is connected between main tank and radiator on the lower side.
Cooling Fans
- It is used to provide cooling of transformers.
Cooling Fan of Transformer
WTI & OTI
- It is used to indicate the winding temperature and oil temperature of the transformer.
📌 Frequently Asked Questions (FAQs) about Transformer Components
🔍 Why is the Low Voltage (LV) winding placed closer to the transformer core than the High Voltage (HV) winding?
The LV winding is placed closer to the core because it requires less insulation from the core, which is grounded. Placing the HV winding outside ensures cost-effective insulation, better cooling, and mechanical strength. This configuration reduces insulation cost and improves transformer efficiency.
💡 What is the function of the conservator tank in a transformer?
The conservator tank provides extra space for insulating oil expansion when the temperature rises. It acts as a reservoir that prevents overflow and maintains proper oil level during thermal fluctuations.
🌬️ What is the role of the breather in a transformer?
The breather maintains the quality of insulating oil by filtering the air that enters and exits the conservator tank. It prevents moisture and dirt from contaminating the oil, thereby extending transformer life.
⚙️ What is a Buchholz relay and how does it work?
A Buchholz relay is a protective device installed between the main tank and conservator. It detects internal faults like insulation failure or oil leakage by sensing gas accumulation and oil flow, triggering alarms or tripping the transformer.
🧯 What is the purpose of the pressure relief pipe in a transformer?
The pressure relief pipe protects the transformer from excessive internal pressure. If pressure builds up due to oil decomposition or faults, the pipe releases it to avoid explosion or damage.
📉 How does a tap changer regulate transformer output voltage?
Tap changers adjust the number of turns in the winding to control the output voltage under load or no-load conditions. This ensures a consistent voltage supply despite fluctuations in load or input voltage.
🔥 Why are radiators and cooling fans important in transformers?
Radiators increase the surface area for heat dissipation of transformer oil, while cooling fans accelerate this process. Together, they maintain permissible temperature limits and enhance transformer performance under heavy loads.
🌡️ What do WTI and OTI indicate in a transformer?
WTI (Winding Temperature Indicator) measures the winding temperature, and OTI (Oil Temperature Indicator) shows the temperature of transformer oil. Both are critical for monitoring and preventing overheating and failures.
🔌 What is the function of bushings in a transformer?
Bushings are insulating devices that allow safe passage of electrical conductors through the transformer tank. They prevent electrical leakage and provide mechanical support to the windings.