How do you cool a dry type transformer?

Dry-type transformers are widely used in power systems due to their excellent safety performance and adaptability to the environment. Their cooling issues are directly related to the transformer’s operating efficiency, lifespan, and safety. Therefore, understanding how to effectively cool dry-type transformers is a critical aspect of ensuring their normal operation.

 Working Principle and Causes of Heating in Dry-Type Transformers

A dry-type transformer is a transformer that uses air as a cooling medium. Its primary working principle is to convert high-voltage current into low-voltage current through electromagnetic induction. During this process, the current flowing through the windings generates a certain amount of heat, mainly due to the following factors:

1. Resistance Loss: Heat loss caused by the transformer winding resistance (I²R loss). When current passes through the conductor, heat is generated due to the presence of resistance.

2. Iron Loss: The transformer's core generates eddy currents and hysteresis losses under the influence of alternating current, thereby producing heat.

3. Load Effect: Under high load conditions, the current increases, and losses also rise, leading to a temperature increase.

Therefore, controlling the temperature of the transformer to avoid overheating is crucial for enhancing its performance and extending its service life.

Cooling Methods for Dry-Type Transformers

The cooling methods for dry-type transformers can generally be divided into natural cooling and forced cooling. Natural cooling refers to relying on the natural convection of air at ambient temperature to dissipate heat, while forced cooling uses additional devices, such as fans or cooling systems, to enhance the cooling effect.

1. Natural Cooling (AN):

Natural cooling is the most commonly used cooling method for dry-type transformers. This method utilizes the airflow inside and outside the transformer to achieve heat dissipation through natural convection. The transformer's outer casing is typically designed with efficient heat-dissipating materials to improve heat dissipation efficiency. Its advantages include a simple structure and ease of maintenance, making it suitable for applications with lighter loads. Natural cooling primarily depends on the ambient temperature and wind speed; hence, it performs poorly in high-temperature or enclosed environments.

2. Forced Cooling (AF):

To address the insufficient heat dissipation of natural cooling under high load conditions, forced cooling was developed. Forced cooling accelerates air movement using fans or other mechanical devices, thereby enhancing the cooling effect. This method can effectively reduce the operating temperature of transformers during high-speed operation, making it suitable for high-load and high-power applications. However, forced cooling consumes more energy than natural cooling; therefore, reasonable balance must be considered in the design.

3. Mixed Cooling:

To accommodate the specific environment and usage conditions of dry-type transformers, a mixed cooling method combines the advantages of natural and forced cooling. Under normal conditions, the transformer relies on natural cooling; however, during heavy loads or high ambient temperatures, the system activates forced cooling to ensure that the transformer’s temperature remains within a safe range. This innovative cooling approach further improves the operational stability and reliability of the transformer.

Temperature Monitoring and Protective Measures

In addition to selecting the appropriate cooling method, temperature monitoring and protective measures are also essential for ensuring the safe operation of dry-type transformers. Modern dry-type transformers are typically equipped with temperature sensors and monitoring systems that track temperature changes in real-time. When the temperature exceeds a set threshold, the system triggers an alarm or automatically activates the cooling equipment to prevent failures due to overheating. Regularly checking the operating status of temperature sensors and cooling devices is necessary for maintaining the safe operation of transformers.

Cooling is a significant aspect of the design and application of dry-type transformers. Through various methods, including natural cooling, forced cooling, and mixed cooling, combined with temperature monitoring and protective measures, it is possible to effectively control the operating temperature of transformers, enhance their performance, and extend their service life. With the advancement of technology, more efficient and intelligent cooling solutions will continue to emerge, further promoting the application and development of dry-type transformers in various power systems. Therefore, understanding and mastering the cooling technology of dry-type transformers is of significant practical importance for ensuring the stability and safety of power systems.