The safe and reliable operation of the twelve-phase synchronous generator-rectifier system is of great significance. This paper analyzes a type of internal short circuit fault of the stator windings in the system

i. e. the phase-to-phase short circuit between the three star-connected phases connected to the same bridge rectifier. A multi-loop mathematical model of twelve-phase synchronous generator-rectifier system with the short circuit fault is set up. In the model

the additional short circuit loop inside the fault phases and its effect on the air-gap magnetic field and circuit topology of the system are taken into account. With the help of the model

electric power quantities such as voltages and currents of stator windings

rotor windings and DC load can be calculated under the fault condition. A series of fault experiments are carried on a special model machine under various load conditions. The experiment data agree well with the simulation results

verifying the correctness of the mathematical model. Based on the simulation results and theoretical analysis

this paper summarizes the electric characteristics of the phase-to-phase short circuit fault between the same group of star-connected phase windings in the twelve-phase machine system. In particular

the features and influencing factors of the short circuit current are treated

which provides a basis for the risk assessment and fault protection of the system. This work is supported by National Natural Science Foundation of China(No. 51277103).