A conventional medium-voltage large-capacity bidirectional chopper used in a battery energy storage system for dc electric railways is equipped with a heavy and bulky inductor for current smoothing. This paper presents the experimental verification of a bidirectional chopper with an auxiliary converter for the purpose of reducing the size and weight of an inductor. The auxiliary converter is formed by the cascade connection of multiple single-phase full-bridge converter cells. Applying the so-called “phase-shifted PWM” to each of the cells can reduce the voltage step across an inductor and increase the ripple frequency, resulting in a significant reduction in size and weight of the inductor. This paper discusses the operating principles and control method of the bidirectional chopper, followed by experiments using a 150-V, 2-kW down-scaled model.