The cause of high frequency transformer temperature increase

a) internal reasons

(1) Internal loss

In the operation of the high-frequency transformer, the hysteresis loss, eddy current loss and copper loss of the coil are converted into heat, so that the temperature rises and the heat is radiated to the surroundings by radiation, conduction, etc., when heat generating and dissipating are balanced, the temperature of each part tends to be stable. The iron loss (hysteresis loss and eddy current loss) is a substantially constant loss, which is related to the structure of the high-frequency transformer, so it cannot be reduced or eliminated during operation; and the copper loss (line loss) changes with load.

(2) Poor contact of the tap-changer

In the high-frequency transformer operation, the tap changer is not enough due to the spring pressure, the junction is small, the junction resistance is increased due to oil film, contamination, etc.. The junction is overheated most often, and the temperature is continuously increased. Especially when the switching tap changer or the high-frequency transformer is overloaded, it is easy to make the tap-changer junction bad contact and overheat. The main reason for the poor contact of the tap changer is that the pressure at the junction point is not enough; there is a sludge film between the static and dynamic contacts; the contact surface has a burn or the positioning indication does not correspond to the switch contact position.

(3) Winding inter-turn short circuit

If several adjacent turns of the high-frequency transformer winding are damaged or aged due to insulation, a closed short-circuit circulating current will occur, which will reduce the number of winding turns, and the short-circuit circulating current will generate high heat to increase the temperature of the transformer. In severe cases, the high-frequency transformer will be burned. When the high-frequency transformer winding is short-circuited between turns, the arc at the short-circuit point causes the various parts and the cooling oil to be heated. When the cooling oil is boiled, it can hear a “beep” sound, causing the temperature of the transformer to rise sharply.

(4) Local overheating of the core

The iron core is made up of insulated silicon steel sheets. During the operation of the high-frequency transformer, the insulation between the silicon steel sheets is damaged due to external force damage or insulation aging and the aging damage of the core-inserted screws. The eddy current is increased, causing local heating. The temperature rise of the transformer oil does not occur. In severe cases, the iron core is partially heated and the oil temperature rises; the no-load loss increases and the insulation decreases.

(5) High-frequency transformer lacks oil or heat pipe blocking

The high-frequency transformer oil is the main insulation inside the transformer, which acts as insulation, cooling and killing. If there is no oil or blockage in the heat-dissipating pipe, the circulating cooling rate of the oil will decrease, resulting in an increase in the temperature of the high-frequency transformer during operation.

(2) External causes

(1) High frequency transformer cooling cycle system failure

In addition to using heat pipe cooling and cooling, the power high-frequency transformer also has a heat dissipation method such as forced oil circulation air cooling and water circulation. Once the cooling system is faulty or the heat dissipation condition is poor, the temperature of the high-frequency transformer in operation will rise (especially during the hot summer season). 

(2) The inlet and outlet of the high-frequency transformer room are blocked or the dust is serious.

The inlet and outlet of the high-frequency transformer room is the passage of air convection during the operation of the transformer. Once the blockage or dust accumulation is serious, the heating condition of the high-frequency transformer does not change and the heat-dissipation condition becomes worse, and the heat can not be dissipated to the surrounding air in time, resulting in high-frequency transformer operation. The temperature rises.

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