The Coil of the Power Transformer
The coil is the most important and complex component in the power transformer. It is made up of copper (or aluminum) wire and is made up of a special insulating component.
1. Spiral coil
The main feature of the spiral coil is that the number of the parallel wires is more root, the wire cake is twisted into a spiral shape, and a wire cake is one turn coil. The spiral coil has good mechanical stability and good heat dissipation technology. It is widely used in the low voltage and large current coils of the transformer. According to the size of the current, spiral coils can be made into three structures, single spiral, double helix and four helix.
2. Continuous coil
A coil is a coil composed of several lines that are distributed along the axis and are not required to be welded to each other, and is called a continuous coil. The end support surface of the continuous coil is large, the axial force is large, the resistance to short circuit is strong, and the heat dissipation capacity of each line section is larger. This coil is widely used in both the voltage level and the capacity range.
3. Interleaved coil
An entangled coil consists of a number of entangled line segments (pancake). All the coils of the tangled line (pancake) are called full – tangle coils, which are widely used in transformers with 220kV and above voltage. A coil consisting of a part of a tangled line (cake) and a part of a continuous line is called a tangled continuous coil, which is applied to a transformer with 66kV and above voltage. Because it inserts non adjacent lines between adjacent lines of the coil, it forms an interlaced entanglement segment and forms a entangled coil, thus increasing the longitudinal capacitance of the coil. The distribution characteristics of the impact voltage on the axial height of the ring are improved, so it has been widely used in various high voltage coils.
4. Inner shielded coil
The internal shielding continuous coil is designed to improve the impact voltage distribution by increasing the series capacitance between the line segments. The characteristic of the structure is to directly connect the additional capacitance lines to the continuous line segments. The ends of the capacitance turn ends are wrapped up after insulation, then suspend in the line segment, and the capacitance lines turn no load current, which only plays a role under the impulse voltage. In the structure, the shielded continuous coil has two segments, four segments, eight segments, and segmented connections.