Problem Definition


Transformers in conjunction with tap changers are utilized in the power industry to regulate the amount of power traveling through transmission lines. The number of windings in a transformer induces a proportionate voltage in the adjacent transmission line. Tap changers are implemented  to alter the number of operational windings in a transformer, and thus the amount of power that passes through the line. 


Fig. A1. Original concept design from our Senior Design predecessors (image courtesy of SEL).
Two years ago the phase-shifting transformer tap changer originated as a senior design project with an emphasis on the electrical workings of the design. This design was to be used for simulating real-life situations in the University of Idaho (UI) power lab for students, and for fault-testing at SEL. The original design team specked and purchased three transformers, and constructed an initial tap changer prototype. However, this prototype needs further refinement with regards a functional make-or-break contact pattern, position locking mechanism, and polarity switch.

Problem Statement

The goal of this project is to design a small-scale, phase-shifting transformer tap changer for implementation in the UI's power lab and for fault testing at SEL.


  • Schweitzer Engineering Laboratory
  • University of Idaho Electrical and Computer Engineering Department
  • Current and future senior design teams
  • University of Idaho students

  • Specific Requirements

    spec sheet

    Our Goal

    This project will focus on the mechanical aspects of the tap changer, and addressing problems incurred by the previous design. These obstacles include implementing an effective make-before-break design, operational position locking mechanism, and a drive and control system. The previously stated concepts are key to producing a successful tap changer that meets the needs and requirements of all stakeholders.