The winding and iron core of the c-type transformer are the primary components for transmitting and converting electromagnetic energy. Keeping them workable is a concern. Statistics show that the iron core problem constitutes a defect, accounting for third place in the total incidents of transformers. The manufacturing part has paid attention to the defects of the transformer core and has made technical improvements in the aspects of the core that can be grounded, the supervision of the core grounding, and the protection of a little grounding. The working part also raises the detection and detection of core defects to an appropriate height. However, the shortcomings of the transformer core still occur frequently, and the reason is mainly due to the multi-point grounding of the core and the poor grounding of the core. The identification and treatment methods of the two types of shortcomings are now introduced.

The reason why the iron core needs a little grounding when it is normal

During the normal operation of the transformer, there is an electric field between the live windings and the tank, and the iron core and other metal components are in this electric field. Due to the uneven distribution of capacitance and different field strengths, if the iron core is not properly grounded, charging and discharging will occur, which will damage the insulation strength of solid insulation and oil, so the iron core must have a point to the ground.

The c-type iron core is composed of silicon steel sheets. In order to reduce the eddy current, there is a certain insulation resistance between the sheets (generally only a few ohms to several tens of ohms). Due to the large capacitance between the sheets, it can be regarded as a path in the alternating electric field. Therefore, Only one point of grounding in the core can clamp the entire stack of core laminations at ground potential.

When the iron core or its metal components are grounded at two or more points (multi-points), a closed-loop will be formed between the connecting addresses, which will bond part of the magnetic flux, induce electromotive force, and form a loop to generate a partial Overheating and even burning the iron core.

As long as the transformer core is grounded at one point, it is a safe and normal grounding. That is, the iron core must be grounded, and it must be grounded at one point.

The shortcomings of the iron core are mainly caused by two reasons. One is that the construction process is poor to form a short circuit, and the other is that the accessories and external elements cause multi-point grounding.

An iron core multi-point grounding-type

(1) After the installation of the transformer is completed, the positioning pins transported on the top cover of the fuel tank are not turned over or removed to form multi-point grounding.

(2) Since the leg plate of the iron core clip is too close to the core column, and the iron core lamination is lifted up for some reason, it touches the leg plate of the clip, forming a multi-point grounding.

(3) The bushing of the iron yoke screw is too long and collides with the iron yoke lamination, forming a new connection address.

(4) The insulating cardboard between the foot of the clip under the iron core and the iron yoke is dropped or damaged so that the laminations at the foot and iron yoke collide to form grounding.