Lesson series

Fundamentals of three-phase electrical transformers

This course covers electromagnetism, voltage and current transformation, ratios and polarity, potential and current transformers, 3-phase transformer construction, transformer classifications, losses and cooling, per unit, etc. The final exam and certification are included.

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 What's included

Electromagnetic forces interact with electrically charged particles and electromagnetic fields; this course will study how these forces lead to voltage & current transformation. Ratios and polarity is also studied leading to the introduction of potential transformers & current transformers, and their use in conjunction with the relevant instruments such as ammeters, voltmeters, watt meters and energy meters. Transformer core construction along with losses & cooling mitigation techniques. 3 phase transformer configurations are studied along with harmonic distortion, CT saturation and on-load tap-changer problems and how these problems are dealt with. Over-current and restraint differential transformer protection is developed along with a look at some examples of " Old School relays" as well as modern IDE (intelligent Electrical Devices) relays.

Transformer Connections: (Y – Y; Delta - Delta; Y - Delta; Delta - Y & Y - Zag Zig) are examined along with Transformer Clock System Vector Nomenclature.

Oil Analysis and the Buchholz Relay are also studied.

 Course Content

  • Chapter 0 - Introduction
  • Chapter 1 - The Ideal Transformer
  • Chapter 2 - The Real Transformer
  • Chapter 3 - Instrument Transformers 
  • Chapter 4 - Three Phase Power Transformers
  • Chapter 5 - Transformer Clock System Vector Nomenclature
  • Chapter 6 - Transformer Construction and Cooling
  • Chapter 7 - Transformer Protection
  • Chapter 8 - Transformer Relays
  • The Final Exam With 24 Questions
Total Course length: 5h 37min

 Who Is This Course For

Engineers; Technologists; Technicians; Electricians; Managers; Supervisors; Superintendents; Electrical Students.


Basic Electrical; Mathematics; Trigonometry.

Graham Van Brunt

Lead Instructor and Founder of PSPT

About Graham Van Brunt

An entire career in the power sector of engineering, Graham graduated from Queen's university coupled with subsequent studies with Wilfrid Laurier University to travel the globe and apply his skills and garner his protection and control experience internationally.
His passion for staying in touch with his profession and his kinship for mentoring has kept him in front of an audience of learners.


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