S11 Three Phase Electric Power Distribution Transformer

S11 Three Phase Electric Power Distribution Transformer

Features
1 Hermetically sealed or breathing tank
For Distribution Transformers, the default construction is the hermetically sealed non-rigid tank completely filled. Air cushion in used with rigid tanks. The variation of oil volume, due to its temperature variation, is absorbed in the flexible fins of the corrugated panels, and in the air cushion when applicable.
Breathing tank with conservator is also a possible configuration.
2. Tank types
The transformer tank is usually of a non rigid structure with corrugated panels, designed to withstand the mechanical stresses, absorb the oil expansion, and meet the thermal evacuation constraints.
For power rating above 3150kVA, the tank is usually designed with rigid structure, cooling radiators and conservator.
3. Cover
For distribution transformers, covers are made of steel plates with bended edges, thus improving the esthetical aspect and reinforcing the cover which is especially important when untanking the unit.
Accessories are mounted on the cover through adequate connectors. Multifunction holes can be provided to receive different type of accessories.
For example, on the same hole, alternatively a DMCR or a pressure relief valve or a thermometer can be mounted.
4. Magnetic circuit
The magnetic circuit is of the three legs construction, Step lap.or GT.
It is made out of a cold rolled, grain oriented silicon steel strips, each strip (0.23, 0.27or 0.30mm thick) being insulated from both sides by Carlite.
5. Winding coils
Both the primary and secondary windings are made of copper or aluminum.
The primary voltage is directly wound on the secondary voltage winding, with insulating barriers and cooling channels between the two windings.
Secondary voltage coils are of rectangular wires or foil conductors. Primary voltage coils are of round enamelled wires, or rectangular paper insulated wires for high power ratings, or round paper insulated wires.
Adequate channels for oil circulation are integrated in the windings to provide an efficient cooling and limit the hot spot temperature.

Typical test values and performances are performed in the painting lab on steel plates during the whole painting process in order to confirm the following:
• Minimum paint thickness film (ISO 2808): 70µm
• Specular gloss factor at 60 Deg (ISO 2813): 90 +/- 5%
• Falling weight test (ISO 6272): 1Kg/050cm
• Erichsen cupping test (ISO 1520): 08mm
• Scratch test (Adhesion ISO 2409): 0
• Bend Test (cylindrical mandrel ISO 1519): 3,0mm
• Salt spray (Fog) test (ISO 7253): Over 1000 Hours