[Objective] As a core component of the synchronous generator excitation system, the accuracy of the equivalent circuit modeling for brushless AC exciters directly determines the reliability of output performance analysis. Traditional equivalent circuit models often overlook the magnetic circuit asymmetry caused by the salient pole effect of AC exciters during parameter equivalence, resulting in systematic deviations between theoretical calculations of commutation reactance parameters and actual operating conditions. These deviations further compromise the evaluation accuracy of key performance indicators, such as AC voltage distortion rate and DC voltage ripple. To address this issue, an improved equivalent circuit modeling method is proposed, with a focus on the influence of the salient pole effect on commutation reactance. [Methods] First, the equivalent circuit model of the brushless AC exciter was derived based on its flux linkage and voltage equations. Second, by analyzing the operational process of the brushless AC exciter over half a cycle in conjunction with the working modes of a three-phase bridge rectifier circuit, the effect of commutation reactance on AC voltage distortion rate and DC voltage ripple was systematically investigated. Finally, a solution for determining commutation reactance under varying salient-pole effect intensities was developed, and a refined commutation reactance calculation model incorporating the salient-pole effect was re-established. [Results] To validate the effectiveness of the model, a two-dimensional transient field-circuit coupling simulation model was established using finite element analysis. Simulation results showed that an increase in commutation reactance significantly increased both the AC voltage distortion rate and DC voltage ripple. The proposed equivalent circuit model, which incorporated the salient-pole effect, exhibited higher accuracy in calculating commutation reactance parameters, with significantly reduced errors compared to conventional methods. [Conclusion] The proposed equivalent circuit modeling method not only offers a high-precision tool for analyzing the commutation characteristics of brushless AC exciters, but also extends to generator systems with rectifier circuits, such as permanent magnet synchronous motors and electrically excited doubly-fed generators. This approach has significant implications for dynamic performance prediction and multi-physics co-optimization of complex electromagnetic devices.