This study aims to develop a Phase Sequence Protector trainer as a learningmedium for the Basic Electrical Energy practicum. The trainer is designed to support students in understanding the principle of phase sequence detection in three-phase systems, addressing the limited availability of practical media that can simulate phasesequence conditions safely and realistically. The research adopts a Research and Development (R&D) approach using the 4D development model, consisting of the define, design, and develop stages. During the validation process, a Likert-scale assessment instrument was employed to obtain quantitative evaluations of the product’s feasibility. Validation was carried out by two media experts and two design experts. The results indicate that the trainer achieved a feasibility percentage of 90.5% for media aspects and 91.65% for design aspects, both categorized as Highly Feasible. Functionally, the trainer successfully detects various phase sequence conditions and provides accurate indicatorresponses. In conclusion, the Phase Sequence Protector trainer is considered suitable for use as an instructional medium and effective in helping students comprehend phase sequence concepts more concretely and applicatively. This product also holds potential for further development as a supporting learning tool in three-phase electrical system courses