Variable Frequency Transformer - State of the Art Review

The Variable Frequency Transformer (VFT) is basically a controllable, bidirectional transmission device that can transfer power in-between asynchronous power system networks. The construction of VFT is similar to conventional asynchronous machines, where the two separate electrical networks are connected to the stator winding and the rotor winding, respectively. One power system is connected with the rotor side of the VFT and another power system is connected with the stator side of the VFT. The electrical power is exchanged between the two networks by magnetic coupling through the air gap of the VFT and both are electrically isolated. This paper gives an overview about core components, commissioning, mechanical design, model, operation, analysis and applications of VFT.