Phase Shifting Winding Structure of Rectifier Transformer
For a rectifying transformer with a phase shifting winding, a meander winding connection, an epitaxial delta winding and a hexagonal winding are generally used. The phase shifting winding and the main winding may be arranged in a radial direction or in an axial direction. In the oil immersed rectifier transformer, a structure in which the phase shifting winding and the main winding are arranged in a radial direction is generally adopted. In the dry rectifier transformer, the structure in which the moving winding and the main winding are axially arranged is more used.
When the main winding and the phase-shifting winding are arranged in the radial direction, under the action of the lightning impulse voltage, the whole winding system is prone to oscillation of the impact potential, resulting in a large voltage gradient between the winding cakes. Some of the wire cake potentials will greatly exceed the amplitude of the incoming wave, especially in the connection between the shed winding and the main winding, and should be paid enough attention in the design of the insulation structure.
The high-voltage winding of a high-voltage epitaxial triangular phase shift product has a winding potential distribution under lightning impulse voltage. The potential of the entire phase shifting winding and a part of the main winding exceeds the amplitude of the input wave, and even at the connection portion of the phase shifting winding and the main winding, it even reaches 160% of the amplitude of the incoming wave. In order to ensure the reliability of this product, the insulation strength of the windings and leads should be properly strengthened on the basis of wave process analysis or model test, the weak points of insulation should be eliminated, and the insulation of the product should be avoided, resulting in insulation during test and operation.