Power transformer components range from internally mounted types, like the core and windings, to externally mounted vent pipes and bushings. These parts work together within the electrical system to ensure the device operates safely and efficiently, with functions that include voltage adjustment, heat dissipation, and monitoring. Below, we examine each of these components and their functions.
What is a Power Transformer Made of?
The power transformer is a complex electrical device with many parts. The various parts enable the device to change voltage from one level to another. They also ensure it safely handles enormous amounts of electrical energy.
At its basic level, the device is an assembly consisting of a magnetic core and windings with many turns of wire. Various other components complete the structure, including electrical insulators, which are placed in different places to serve as isolators.
The entire construction is housed in a steel or aluminum enclosure and immersed in mineral oil or supplied with vents for cooling. Each part has a role to play in the working of the transformer, as the following section will help you understand.
What are the Components of a Transformer
The components of a power transformer can be large-sized, such as the core and windings, or compact, like explosion vents. The list below has all the basic parts, including their working and function, explained in detail.
1.Main Tank
The main tank is the metal housing enclosing and protecting the transformer parts, including the windings, core, and many others. It also contains the cooling and insulating oil and grounds the various circuits, ensuring safety and other electrical properties.
The tank material is typically carbon steel and sometimes aluminum. Designs also vary depending on factors such as application requirements and core design or construction.
2.Steel Core
The core is the heaviest of all power transformer components. It supports the windings and comprises thin steel sheets of less than a millimeter stacked together to form a solid structure. For insulation, each sheet has a non-conductive layer covering its surface.
The laminated core construction and insulation help reduce eddy current and hysteresis losses. The steel used for the core has a high magnetic permeability. This property means it offers a low reluctance path for transmitting the magnetic flux that transfers electrical energy from one coil to another.
3.Coil Windings
These are turns of wire wound around the core. The wires are mainly copper and sometimes aluminum. Copper possesses superior electrical properties and other characteristics, making it a better choice in many applications.
A power transformer uses two or more coils in primary and secondary winding. The primary winding is the input voltage is applied side, and the secondary is the output, with the spaces between turns filled with insulating material like paper. Individual wires also have varnish or paper insulations.
4.Insulating Materials
Power transformer insulators electrically isolate sections and components. For instance, they separate the windings from the core, individual turns of the coil windings, and several other parts.
The materials can be solid, like paper and pressboard, or liquid, like mineral oil. Oil is a better insulator in most applications. It has a longer life, offers better insulation properties, and can even serve a cooling function.
5.Cooling System
The cooling system is an elaborate mechanism that helps remove heat using airflow, mineral oil, and sometimes water or both oil and air. The type of medium used depends on the device size.
Large transformers are oil-cooled, while smaller ones are air-cooled. An oil system immerses components in mineral oil and may use a radiator or narrow cooling tubes to speed up dissipation.
Air systems, on the other hand, use natural or forced circulation. A forced circulation system employs fans, while a natural version contains vents to allow unrestricted airflow.
6.Tap changers
Tap changers are mechanical parts used in devices built with additional turns in the secondary, high voltage (HV) windings. Their function is to adjust the number of turns and regulate the output voltage to the desired level, which can be high or low.
There are two types of tap changers: on-load and offload. On-load types adjust voltage while the transformer is loaded and supplying current. With offload tap changers, you must disconnect the load first.
7.Explosion Vent
The explosion vent is a safety component mounted above the conservator reservoir. It’s typically a small metal pipe with one end covered by a diaphragm. The vent is an emergency exit for hot, expanding oil and gases.
During a fault, it provides a path of least resistance for pressure to escape into the atmosphere. This function helps relieve the tank of pressure, preventing a possible explosion. Only the diaphragm gets damaged.
8.Oil Conservator
The conservator is a small cylindrical part positioned above the main tank. It acts as the transformer oil reservoir, providing space for expansion and contraction due to temperature changes. It also ensures the tank is always full and often has a breather pipe attached. A level indicator mounted to it shows the oil level.
9.Air Breather
This part is an optional part mounted on the conservator. It contains a silica gel that absorbs moisture from the air. Moisture ingress would cause the oil to degrade, reducing its lifespan. The excess humidity could also corrode various parts. The action of the air breather helps prevent that.
10.Bushings
These are hollow, porcelain, or epoxy resin components above the main tank where the device supplies the output voltage. They insulate the high-energy terminals that connect the device to an external electrical system from the grounded tank.
11.Drain Valve
The drain valve, conveniently positioned at the bottom of the main tank, is an opening for letting out oil. It allows operators to empty and refill the tank during maintenance. It works like a regular faucet and can use various mechanisms to open and close.
12.Oil, Temperature & Pressure Gauges
Various gauges serve the essential function of monitoring different parts and operations. They help ensure safety and functionality, alerting operators when measurements reach dangerous levels.
One of the most critical is the temperature gauge, which monitors the temperature of oil and windings to prevent overheating. Others include oil flow indicators and pressure gauges.
13.Buchholz Relay
This safety component activates the trip circuit during a fault, and its location is conveniently in the conservator. The relay also triggers the alarm circuit.
Buchholz relays are oil-cooled transformer safety components. They work by sensing oil leakages and other fault signs, such as increased oil flow and excessive heat to close contacts. The relay will also react to the gases that result from faults.
Conclusion
Various power transformer components work together to change the voltage from low to high or vice versa. The core and windings are the most significant. They also serve the most critical function of all. Other parts ensure this high-energy device operates as it should. They include support and safety monitoring components to prevent or detect faults.