The Electromagnetic Design And Parameter Calculation Of Powerformer By Fem

Powerformer is a new type of high voltage generator, of which the stator winding consists of XLPE cables. These cables have cylindrical cross-section. The circular conductor yields an even electric field distribution around its entire circumference, which makes that the output voltage can reach the power grid voltage level. So Powerformer offers a direct connection to the power grid without the help for a step-up transformer. It offers the power plant several advantages such as enhanced reliability, higher efficiency etc. As a new type of energy conversion device, Powerformer is different from the conventional generator in stator structure and Powerformer'performance is also influenced by the mechanical and electrical character of cable. Therefore it is difficult to design the Powerformer exactly with the conventional electromagnetic design method. Firstly, theory, structure, characteristics and development survey of Powerformer are introduced as well as high voltage cable. The design method of stator primary dimension and slot shape in Powerformer is determined according to the character and size of cable. The stator inner diameter of Powerformer is calculated according to the bend radius of cable and the slot shape is determined by the outer diameter of cable, a rated voltage 35kV and rated power 2550kW Powerformer is designed on the basis of this design method. Secondly, the end region leakage reactance and slot leakage reactance are calculated by the FEM software-ANSYS. Modeling and resolving process of end region leakage reactance is introduced detailedly. Three type of slot shape are discussed respectively when calculated the slot reactance, which including round-shape slot, semicircular shape slot and rectangle slot, the calculation method of semicircular shape slot leakage reactance is determined by the analytic solution of round-shape slot and rectangle slot leakage reactance. Finally, the theory of 2D finite element method, with which reactance parameters were calculated, is introduced in detail. The parameters include the steady reactance, transient and sub-transient reactance of Powerformer. The 2D model was established and the steady reactance, transient and sub-transient reactance are calculated with the finite element software-ANSYS. The electromagnetic parameter of Powerformer with FEM and the design result were compared in order to determine the calculation method of steady parameter.