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Analysis of Temperature Rise of High-frequency Transformer
Mar 10, 2018

    

        Analysis of Temperature Rise of High-frequency Transformer


The temperature rise of high-frequency transformers is inevitable during the actual operation of the transformer, but we should control the temperature rise of the high-frequency transformers. The various transformer departments also have different allowable temperature rises. Different operating conditions are also different. Allow temperature rise. The nameplate of a general transformer will specify its rated temperature rise. He refers to the temperature at which the transformer generates heat that is higher than the "standard environment." For an oil-immersed transformer, its value is equal to the upper oil temperature of the transformer minus the “standard ambient temperature”; for a dry-type transformer, its value is equal to the transformer winding temperature minus the “standard ambient temperature”. The factors that determine the allowable temperature rise are: life expectancy of the transformer, safe operation of the transformer, and detection technology of the transformer.


In transformer life, the main cause of insulation aging is temperature. Because the internal heat of the transformer is not evenly spread, the temperature of each part of the transformer varies greatly. Therefore, it is necessary to specify the temperature rise of each part when the transformer is rated. This is the allowable temperature rise of the transformer. General oil-immersed transformers are Class A insulation with a maximum allowable temperature of 105°C. Each part allows temperature rise to:

The

Coils allow a temperature rise of 65°C. Based on A-grade insulation at 105°C, when the ambient temperature is 40°C, 105°C-40°C=65°C. Since the temperature of the transformer is generally 10°C lower than the winding, the allowable temperature rise of the transformer oil is 55°C.

To prevent oil aging, the temperature rise of the upper oil level must not exceed 45°C. In this way, no matter how the ambient air changes, only if the temperature rise does not exceed the allowable value, the transformer can be guaranteed to operate safely within the specified service life.

The temperature rise of the oil-immersed transformer: the upper oil 55 degrees, the winding 65 degrees, the tank and the structural parts indicate 80 degrees.

Dry-type transformer temperature rise: Winding, Class A insulation 60 degrees, Class B insulation 80 degrees, Class C insulation 150 degrees, Class E insulation 75 degrees, Class F insulation 100 degrees, H pole insulation 125 degrees.

When the ambient air temperature drops a lot, the heat dissipation capability of the transformer's enclosure will increase, while the heat dissipation inside the transformer will increase little. When the transformer is operated with a large load or an overload, although sometimes the upper oil temperature of the transformer has not exceeded the specified value, the temperature rise exceeds a lot, and the coil is overheated. Therefore, such operation is not allowed.

When the transformer is in operation, there will inevitably be a short circuit. When the transformer is short-circuited, the short-circuit current will flow. At this time,

 

There are still a few points to pay attention to when studying transformer allowable temperature rise:

(1) There must be no dead zone under the lid.

(2) The heat sink center of the heat sink is higher than the heat center.

(3) The core temperature of dry-type transformers will affect the temperature rise of the core windings.

(4) The radiator or cooler enters the oil in the tank to allow it to flow into the windings and cannot be short-circuited in the space outside the winding.

(5) When doing the temperature rise test, the external heat should not be poured into the transformer. For example, if the current density of the shorting lead is too large, this is the case.

(6) The sensors embedded in the windings can be led out by the optical fiber to measure the hot spot temperature of the windings. In this way, the super brand-name running ability of the transformer can be measured.

(7) There must be no air left in the radiator, and there must be a vent plug on the radiator. Before the temperature rise test, vent the air.

 

The above is an analysis of the temperature rise of the high frequency transformer summarized by Xiao Bian for everyone. This article analyzes the conditions of the allowable temperature rise of the high frequency transformer under different conditions, and analyzes how to analyze the temperature rise of the transformer. Some things to pay attention to, for your reference, if there are any problems, this site will be updated every week, one or two related articles in this topic, for the convenience of everyone to view, you can collect this site. Now if you still want to learn more about the switching power transformer technology, price, etc., then click on the switch power transformer information.


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