Finite element analysis of a Virtual Air Gap Variable Transformer

A variable transformer has many applications in the power industry. It is usually implemented by physically changing the winding ratio through mechanical or electronic switches. The virtual air gap technique allows an effective change of the winding ratio through an electronic flux routing technique. This papers presents a finite element method (FEM) analysis of the virtual air gap variable transformer (VAG-VT) that demonstrates the behaviour of the variable transformer with virtual air gap. It is shown through both static and transient analysis that a variable winding ratio can be achieved. The transient simulation shows that this variable ratio is not constant over a complete cycle, thus additional control is required to achieve a constant winding ratio.