This new cable represents a decisive improvement for the CTC. It has been created to improve the thermal performances of the CTC by increasing the surface of contact between the strips and the cooling oil. In this new cable one, or even more, oil ducts through the cross section of the CTC have been created with a special bending of the strips. The resulting geometry increases the surface in contact with the oil, thus giving a potential advantage to the transformer in terms of efficiency. For a details please refer to the following article: “Ventilated CTC, the latest development of the cables for transformers”
The Stranding Cage is a modular structure made of disks connected through a central tube holding 8 or 10 bobbins, depending on the type. It is supported by idle wheels.
The bobbins are loaded on cradles shaped as open forks and clamped by pneumatic tailstocks. The axis of rotation of the forks is convergent to the center line to minimize the angular deviation of the strips.
The strips are tensioned by an adjustable block brake. The braking force is limited to a minimum, enough to avoid the unrolling while stopping the line. This prevents from jerks on the bobbin due to the dropping down of the strip from its layer.
Each strip is guided inside plastic tubes, thus making easier the threading of the machine.
The cage is moved by an high torque electric motor with gear reducer.
Emergency stop and cage retention is made by multiple pneumatic brakes.
This machine bends the strips in the vertical plane to get a slot in the middle height of the CTC through its whole length.
This slot increases the thermal exchange between copper and coolant by introducing an additional surface. The folding of the flat wires is made by elettrodynamic clamps. The machine is powered by several servo-motors controlled through PLC by axis cards. The setting of the machine is assisted by computer. The controls are made and displayed on a color touch screen panel hanging from the top of the structure through a pivoting arm.
The machine operates according to a new transposing principle that makes use of rollers for displacing the strips from one stack to the other. This innovative principle allows a very smooth, precise and fast bending shape without any damage to the enamel in the edges. The original configuration of the machine, made of two opposite transposing heads, allows an easier handling of the CTC. The two opposite heads can be independently moved up and down to fit either different heights of the cable or different positions of the center line. The heads can also be opened to a max stroke in order to allow the total release of the cable. The machine is powered by a servo-motor. The setting of the operation parameters is made on a control panel connected to a dedicated PLC. The data are displayed on an LCD colour screen. This control panel, with its keyboard, is hanging from the machine top by a pivoting arm; this results in a very ergonomic working position.
The machine is composed of a rigid frame holding the pulling group that can rotate 90° around its longitudinal axis to clamp the cable from top or side, depending on which condition is more effective. The cable is pressed between and pulled by two reinforced wear-resistant belts. The clamping pressure is given by pneumatic pistons through groups of swinging rollers. At both ends of the machine two groups of adjusting rollers keep the cable centered. The machine is driven by two independent AC motors working as electric differential device. All settings are made on a control panel on board, that includes also the valves for the air pressure regulation.
This take-up is a portal type self-traversing on rails by means of a servo motor for a precise winding of the cable. The reversing position is controlled by an encoder and protected by limit switches. The bobbins are clamped by tailstocks that can close/open and move up/down by means of independent servo motors. The winding is controlled either by pull or by speed, in order to properly operate with a wide range of cables. The machine is equipped with dedicated control panels, one mounted on a separate column, and two mounted on the side uprights. The machine is also equipped with an adjustable cable guide.