Seamless star-delta winding changeover circuit for AC generators

This paper proposes a circuit, which can change the winding connection of a generator from the star connection mode to the delta connection mode by changing the circuit operation. In the conventional method, the outage time exits during the dead-time of two magnet contactors. Therefore, the generator current cannot maintain its continuity. Moreover, the surge voltage occurs in the terminal of the generator. In order to achieve the seamless winding changeover, this paper proposes a new circuit, which consists of a PWM rectifier, a diode bridge rectifier and three additional switches. From the simulation results, the transition from the star connection mode to the delta connection mode, and the continuous generator current during the transition time are confirmed. In addition, it is confirmed that the current THD can reduce by supplying the reactive current with the generator of the delta connection mode. When the generator has percent reactance of 30%, the current THD is improved from 19% to 3%.