Load selector for varying the transformation ratio of three-phase transformers having windings connected in delta

摘要

In the case of such load selectors, the stationary selector contacts (8) of each of the three phases normally lie in in each case one plane (1, 2, 3), (located at right angles to the apparatus axis), distributed over the circumference of an insulating cylinder (6), and a preselector having stationary preselector contacts (8.1) is provided on planes (4, 5, 4') (which likewise lie at right angles to the apparatus axis) in order to enlarge the range of variation which can be set. According to the invention, a further chamber (18) for accommodating the preselector contacts (8.1) is provided coaxially underneath a chamber (17) for the selector contacts (8) on the insulating cylinder (6) whose diameter is the same over its entire length, and mutually corresponding preselector contacts (8.1) of the three phases in each case lie on a plane (10) (which intersects the apparatus axis at an acute angle) on an ellipse and at the same time form the corners of an approximately equilateral triangle. Advantageous solutions result especially in the case of an arrangement of the preselector contacts (8.1) of in each case at least one phase at an apex of this ellipse. A structure of load selectors according to the invention also makes it possible (if the cylinder diameters are relatively small) to provide a sufficiently large distance between the preselector contacts (8.1) to be insulated from one another, for rated voltages up to at least 400 kV, and said structure is thus particularly suitable for load selectors for high output voltages. IMAGE