​What is the temperature of a dry transformer?

Dry type transformers run at much higher temperatures compared to oil filled ones. Their limits come from the insulation class and overall design. They do not use any liquid for cooling like those other types do. Instead, these rely on air moving around and solid materials to handle the heat.

People classify dry type transformers based on insulation classes. Each class sets the highest temperature rise allowed. Class B allows up to 130 degrees Celsius total. That means an 80 degree rise over the surrounding air. Class F goes to 155 degrees Celsius. It permits a 100 degree rise above ambient. Class H reaches 180 degrees Celsius. This one allows a 125 degree rise over ambient.

These ratings mean the max rise above a usual 40 degree ambient setup. Take a Class F unit for instance. It can handle 155 degrees total. That breaks down to 100 degrees rise plus the 40 degrees outside.

In everyday use, dry type transformers keep certain temperatures steady. The average in the windings rises 80 to 115 degrees above ambient. Hot spots end up 10 to 15 degrees hotter than that average. Surfaces stay at 70 to 90 degrees for safety reasons. The design covers ambient from minus 20 to plus 40 degrees.

Newer dry type transformers come with ways to watch temperatures closely. They include sensors like PT100 RTDs right in the windings for accurate readings. Thermal systems kick in fans automatically when temps hit set points. Alarms warn early at 130 degrees for Class F models. Trips shut things down at 155 degrees for those same units.

Various things can change how hot these transformers actually get. Load levels make temps go up as you push more power through. Warmer outside air cuts down on how well cooling works. Poor ventilation might add 10 to 20 degrees extra. Running above 1000 meters needs some derating because air gets thinner up there.

Managing temperatures right matters a lot for these units. Keeping 10 degrees over the rated level cuts insulation life in half. Surfaces have to stay cool enough to avoid igniting nearby stuff. You can overload temporarily if there is enough margin in the temps.

Designers build dry type transformers to handle these higher temps safely. Advanced materials in the insulation provide reliability over time. They keep operations fire safe even inside buildings.