Under rainy weather conditions, dry-type transformers are prone to water ingress, which can easily cause short circuits. So, how should dry-type transformers be treated after water ingress

Firstly, we can use a megohmmeter to record the insulation resistance between the high and low coils to ground (iron core) and between the high and low voltage coils. Based on the values you record, we can check whether the degree of moisture is severe. Generally, if it is above 200M Ω, it indicates that the moisture is very severe. First, we can use some methods to dry the transformer. If there is a drying room, it is very simple. The temperature should be gradually increased to around 100 degrees Celsius and maintained for 4 hours. If conditions permit, high-power air blowers can also be used for drying. If the moisture is not very severe, an effective solution is to apply low voltage electricity, and the moisture will naturally evaporate.

The root cause of internal vibration in dry-type transformers is magnetostriction caused by alternating magnetic flux in the iron core.

The size of noise is related to magnetic flux density, iron core joint condition, iron core clamping force, etc., especially when it is closely related to magnetic flux density. The higher the magnetic flux density, the more intense the vibration and the louder the sound.

Another reason is that long-term vibration may cause the iron core joints to enlarge, the iron core to loosen, and so on, which will further intensify the vibration and make the sound louder.

Another type of sound comes from eddy currents, which are related to the material and structure of the iron core and should be minimized during design. However, eddy currents are inevitable and can also produce a buzzing sound.