What is the Operating Temperature of a Dry-type Transformer?

Temperature is a core indicator for the safe operation of dry-type transformers, directly related to equipment lifespan and power supply stability, and is also a key focus for procurement and maintenance. As a transformer manufacturer, this article, based on practical experience, breaks down the three temperature ranges of dry-type transformers: normal operation, temperature rise limits, and extreme tolerance, and shares influencing factors and control techniques to provide precise guidance for users.

Temperature Ranges of Dry-Type Transformers

The temperature range of dry-type transformers needs to distinguish between "normal operating temperature," "temperature rise limit," and "extreme tolerance temperature."  Different materials and insulation grades have clearly defined numerical standards, which are the core basis for procurement and maintenance.

Normal Operating Temperature Range

For mainstream F-class insulation, all-copper winding dry-type transformers (such as SCB11 and SCB13 series), the core temperature during normal operation is recommended to be controlled between 80℃ and 100℃, and the winding temperature between 90℃ and 110℃. Within this temperature range, equipment losses are at a reasonable level, the insulation layer ages slowly, and the designed service life of 25-30 years can be guaranteed. In actual applications, in conventional scenarios such as commercial complexes and ordinary factories, the daily load rate of the equipment is mostly between 50% and 70%, and the temperature usually stabilizes between 85℃ and 105℃, which is an ideal operating state.

If it is an H-class insulation dry-type transformer (mostly used in high-temperature, high-load special scenarios), the normal operating temperature can be appropriately increased, and the winding temperature should be controlled between 100℃ and 120℃. Its high-temperature resistant insulation material can adapt to more demanding operating environments, commonly found in metallurgy, chemical industry, and other high-temperature working conditions.

Temperature Rise Limits

According to the GB 1094.11-2023 national standard, there are clear regulations on the temperature rise limits of dry-type transformers (based on an ambient temperature of 20℃). This is a rigid indicator for equipment design and operation; exceeding the limit will accelerate insulation aging and even cause failures. Core Limit Standards: For F-class insulated dry-type transformers, the winding temperature rise limit is 100K (i.e., the winding temperature does not exceed 120°C), and the temperature rise limit for the core and structural components is 80K; for H-class insulated dry-type transformers, the winding temperature rise limit is 125K (winding temperature does not exceed 145°C), and the temperature rise limit for the core and structural components is 100K. It should be noted that temperature rise is the "difference between the equipment temperature and the ambient temperature." If the ambient temperature reaches 35°C in summer, the maximum allowable temperature for F-class insulated windings is 35°C + 100K = 135°C, but this temperature can only be tolerated for a short period and is not suitable for long-term operation.

Extreme Temperature Tolerance

Dry-type transformers have the ability to withstand high temperatures for short periods, but this is only applicable to sudden load fluctuations or emergency situations. For F-class insulated equipment, the short-term (no more than 2 hours) extreme temperature tolerance is no more than 150°C; for H-class insulated equipment, the short-term extreme temperature tolerance is no more than 180°C. Exceeding this temperature will cause irreversible damage to the insulation layer, such as epoxy resin cracking and winding insulation breakdown, which in severe cases can directly lead to equipment burnout, causing production downtime or power outages.

A reminder from the manufacturer: Some users, in pursuit of increased production capacity, operate dry-type transformers under overload conditions for extended periods, causing the winding temperature to approach or exceed the limit. This practice will shorten the equipment lifespan from 30 years to 5-8 years, and the subsequent repair costs will far outweigh the initial gains, resulting in a net loss.

Factors Affecting Dry-Type Transformer Temperature

Load Rate

The load rate is the most direct factor affecting the temperature of dry-type transformers. The higher the load rate, the greater the winding loss (copper loss) and core loss (iron loss), and the more heat is generated. When the load rate increases from 50% to 100%, the winding temperature usually rises by 30°C-40°C; if the load rate exceeds 120% (overload operation), the temperature will rise exponentially, and can approach the extreme temperature tolerance within 1 hour. When our factory ships equipment, we specify a recommended load rate range based on the application scenario.  For standard models, we recommend a long-term load rate not exceeding 80%, while specially customized models can be adapted for continuous operation at 100% of the rated load.

Insulation Class and Materials

The insulation material class determines the upper limit of temperature resistance for dry-type transformers. Class F insulation (epoxy resin + fiberglass) is currently the mainstream in industrial and commercial applications, offering a balance of cost-effectiveness and high-temperature performance; Class H insulation (Nomex paper + epoxy resin) has stronger high-temperature resistance, but the purchase cost is 15%-20% higher than Class F.  At the same time, the winding material also affects heat dissipation efficiency. Full copper windings have 15%-20% better heat dissipation performance than aluminum windings. Under the same load, the temperature of full copper models is 10℃-15℃ lower than that of aluminum winding models. This is the core reason why our factory's mid-to-high-end models are all equipped with full copper windings as standard.

Cooling Method

Dry-type transformer cooling methods include natural air cooling (AN) and forced air cooling (AF), which directly affect temperature control capabilities. Natural air cooling is suitable for scenarios with low load rates and suitable ambient temperatures, ensuring that the equipment temperature remains within limits under rated load; forced air cooling, through the addition of fans for active heat dissipation, allows the equipment to maintain a safe temperature range even under 120%-150% overload conditions, making it suitable for high-temperature, high-load scenarios such as data centers and metallurgy. Our factory can customize the cooling system according to the application requirements to ensure that the temperature meets the standards under different operating conditions.

Operating Environment

Ambient temperature and ventilation conditions directly affect the equipment's heat dissipation effect. For dry-type transformers used outdoors or in high-temperature workshops, the equipment operating temperature will increase by 8℃-12℃ for every 10℃ increase in ambient temperature during the summer; if the equipment is installed in a confined space with poor ventilation, the heat cannot be dissipated in time, leading to a "heat accumulation effect" and a continuous rise in temperature. In addition, dust and humidity in the environment will also affect heat dissipation. In dusty environments, the equipment surface needs to be cleaned regularly, and in high-humidity environments, it is recommended to use models with a protection rating of IP30 or higher to prevent moisture from affecting the insulation layer and heat dissipation. Manufacturer's Practical Recommendations: Temperature Control and Fault Warning Techniques

Precise Monitoring

When purchasing dry-type transformers, it is recommended to select a smart temperature controller to monitor winding and core temperatures in real time and set up a three-level warning system: Level 1 warning (approaching 80% of the temperature rise limit) to remind maintenance personnel to pay attention to load changes; Level 2 warning (approaching 90% of the temperature rise limit) to automatically activate forced air cooling (if configured); Level 3 warning (reaching the temperature rise limit) to trigger power-off protection and prevent equipment damage. Our factory's standard smart temperature controller supports remote monitoring and data traceability, allowing maintenance personnel to easily monitor the equipment's temperature status in real time.

Rational Selection

Selecting the appropriate model based on the load characteristics and ambient temperature of the application scenario is crucial for temperature control. For conventional industrial and commercial scenarios, F-class insulation, all-copper windings, and naturally air-cooled models are sufficient; for high-temperature and high-load scenarios, H-class insulation and forced air-cooled models should be prioritized, with a 10%-20% load redundancy to avoid overheating due to overload. Our factory provides free selection services, customizing suitable dry-type transformers based on the application's load data and environmental parameters, thus mitigating temperature risks from the source.

Daily Maintenance

Regularly clean dust from the equipment surface and cooling channels to ensure smooth ventilation; inspect the temperature controller data at least once a month, and check the cooling fan's operating status quarterly (if configured); avoid prolonged overload operation of the equipment. If temporary overload is necessary, check temperature changes in advance and control the overload duration; during high-temperature periods in summer, reduce the equipment operating temperature by adjusting the production load and enhancing environmental ventilation (such as installing exhaust fans).

Troubleshooting

If the dry-type transformer temperature rises abnormally (more than 15℃ above the normal range), the cause must be investigated immediately: first, check if the load rate is exceeded; if overloaded, reduce the load promptly; second, check if the cooling system is operating normally; if the fan is faulty, shut down the equipment immediately for repair; if there are no abnormalities in the load and cooling system, check for winding short circuits or insulation aging. It is recommended to contact the manufacturer's professional personnel for inspection to avoid secondary damage caused by self-disassembly. Our factory provides 24-hour emergency repair services to ensure that temperature-related malfunctions are resolved quickly.

Industry Misconceptions

Misconception 1: Lower temperature is always better. In reality, dry-type transformers have an "optimal temperature range" (80℃-110℃) during operation.  Temperatures that are too low lead to increased losses and energy consumption; long-term low-temperature operation is actually detrimental to equipment efficiency.

Misconception 2: All dry-type transformers have the same temperature standards. Equipment with different insulation classes and cooling methods have significantly different temperature ranges.  Judgment must be based on equipment parameters and application requirements; a one-size-fits-all approach is incorrect.

Misconception 3: Only winding temperature needs to be monitored. Excessive core temperature also affects equipment lifespan, especially as the silicon steel sheets in the core age, increasing iron losses and triggering a chain reaction of temperature increases. Both winding and core temperatures must be monitored.

In summary, controlling the temperature range of dry-type transformers hinges on the combination of "appropriate selection, precise monitoring, and daily maintenance." As a manufacturer, we recommend that users prioritize all-copper windings and insulation classes and cooling methods that are suitable for the application when purchasing. During operation, strictly adhere to temperature standards and promptly address abnormal situations to ensure the equipment operates within a safe temperature range, maximizing lifespan and reducing maintenance costs. If you require a customized dry-type transformer for a specific application or need a dedicated temperature control solution, please contact us directly.  Providing details of your application will allow us to offer professional support.