Detailed explanation of transformer temperature rise
When discussing transformer performance, "temperature rise" is often an easily overlooked parameter. Buyers usually pay more attention to the rated capacity, voltage, insulation level and price, and leave the temperature rise issue to the technical team to deal with. However, in actual operation, the temperature rise is directly related to the service life, efficiency and reliability of the transformer.
Transformers inevitably generate heat when converting electrical energy. Part of the energy is lost in the iron core, and when current flows through the winding, the winding will also generate additional heat. The role of the cooling system is to dissipate this heat and ensure that the transformer is kept within the allowable operating temperature range.
What is transformer temperature rise?
Transformer temperature rise refers to the difference between the temperature of a certain component of the transformer and the temperature of the surrounding cooling medium.
For example, if the surrounding air temperature is 30°C and the average winding temperature is 95°C, the winding temperature rise is about 65K.The temperature rise is not equivalent to the actual operating temperature, because the ambient temperature also needs to be considered.
This is particularly important when comparing transformers used in different countries or environments. Even if the rated temperature rise of the two transformers is the same, the actual temperature of one transformer operating in a cool indoor distribution room may be very different from that of the other outdoor transformer installed in a hot climate. For more information about transformer construction and specifications, see our Dry-Type Transformers.
Where does the heat come from?
The heat inside the transformer mainly comes from two aspects.
The first is the no-load loss, which is mainly due to the magnetic core. As long as the transformer is charged, this loss will exist even if the load is very low.
The second is the load loss, which is mainly related to the winding resistance and current. As the load increases, the winding loss will also increase, so the temperature of the transformer will usually increase under heavy load.
Because of this, the temperature condition of the transformer cannot be judged only based on the rated capacity on the nameplate. The actual load mode, environmental conditions, and cooling method will all have an impact.
Why is temperature rise important?
If the transformer is operated at excessive temperatures for a long time, the aging of the insulation material will be accelerated. Once the insulation performance decreases, the transformer is more prone to electrical failure and its service life will be shortened.
On the other hand, a low temperature rise does not mean that the transformer is the best choice. To achieve lower temperature rise, it is often necessary to use higher-quality materials, larger heat dissipation area, more powerful cooling equipment or different structural designs. These factors may increase the initial cost.
For most projects, the pragmatic goal is to select the transformer with the appropriate temperature rise level according to the expected operating conditions, rather than blindly pursuing the lowest temperature rise value.
What factors affect the temperature rise of the transformer?
The load level is one of the most obvious factors. Compared with light-load operation, transformers operating at close to rated capacity usually generate more heat.
Ambient temperature is also crucial. In hot areas, the efficiency of the transformer dissipating heat to the surrounding air will be reduced. This is of particular concern for outdoor substations and projects located in Africa, the Middle East or other high-temperature regions.
Cooling method is another important consideration. Depending on the capacity and application scenarios, different cooling schemes will be used in transformer design. In addition, good ventilation conditions around the transformer can also significantly improve the heat dissipation effect.
The design of the iron core and winding cannot be ignored. The use of high-quality magnetic steel, the selection of suitable wires and the reasonable winding design help to control loss and temperature rise.
When these conditions are different from standard operating environments, the transformer may need a different design. Our Dry-Type Transformers can be configured according to project requirements such as capacity, voltage, cooling arrangement and installation conditions.
How should buyers evaluate temperature rise indicators?
When evaluating the transformer quotation, the temperature rise index should be considered in conjunction with the operating conditions. It is recommended to learn more about the rated load, ambient temperature, cooling method and applicable technical standards from the supplier.
For projects involving continuous heavy loads, restricted ventilation, or high ambient temperatures, these requirements should be fully communicated before the transformer is manufactured. Standard models may not always be the most suitable choice.
Kechang can flexibly adjust the transformer design according to project requirements (including rated capacity, voltage, cooling scheme and installation conditions, etc.). Before delivery, the transformer will be inspected and tested in strict accordance with the agreed technical requirements.
After all, the temperature rise is not only a number on the specification sheet, but also one of the key indicators to measure the performance of the transformer after it is shipped out of the factory and put into actual power system operation.
One-stop Electrical Solutions in China
At Kechang, we provide dry-type transformers and other transformer solutions for different project requirements. Contact our team to discuss your capacity, voltage, cooling and installation conditions.
