In this paper, we introduce the control mode of excitation regulator with constant α. WL-06B double-microcomputer excitation regulator in Shenwo power plant of Liaoning province is taken as an example. By changing the induction generator from self-shunted type into separately-excited type, we carry out three-phase short-circuit test for steady-state characteristics of generator, and obtain characteristic curve of the test. Moreover, we obtain the three-phase current of stator winding by altering the control angle and excitation current of rotor winding. We can also determine the symmetry of three-phase current and identify short-circuit failures among windings of rotor by using the characteristic curve. The research results offer reference for similar tests in the future.