In Chapter 1, we gained an overview of distribution electrical transformers and
their role in the power distribution system. Now, let us delve into the fundamental
principles that underpin the operation of transformers. Understanding these
principles is crucial for comprehending the inner workings of distribution
transformers and their ability to transform voltage levels.
Understanding Electromagnetism:
• To comprehend how transformers operate, it is necessary to grasp the basics of electromagnetism. Electromagnetism is the branch of physics that deals with the interaction of electric currents or fields and magnetic fields. Key concepts include electric charge, electric current, magnetic fields, and
electromagnetic induction.
Transformer Operation and Core Principles:
• A distribution transformer consists of two essential components: a primary winding and a secondary winding, both wound around a magnetic core. The core is typically made of high-permeability materials such as laminated silicon steel, which facilitate magnetic flux flow.
• When an alternating current (AC) flows through the primary winding, it generates an alternating magnetic field in the core. This alternating magnetic field induces a corresponding alternating voltage in the secondary winding, thanks to the principle of electromagnetic induction. The voltage induced in the secondary winding is directly proportional to the turns ratio between the
primary and secondary windings.
Transformer Types and Configurations:
Transformers come in various types and configurations to meet specific voltage
requirements and applications. The most common types include:
1- Single-Phase Transformers: Single-phase transformers are used for residential and small commercial applications. They have a primary and secondary winding, providing a step-down or step-up voltage transformation.
2- Three-Phase Transformers: Three-phase transformers are employed in industrial and commercial settings, where three-phase electrical power is prevalent. They consist of three sets of windings, each connected to a different phase, enabling efficient three-phase voltage transformation.
3- Auto Transformers: Auto transformers are a special type of transformer where a portion of the winding serves as both the primary and secondary winding. Auto transformers are used for voltage adjustments, as they provide a variable or tapped output voltage.
Transformer Equations and Voltage Ratios:
• Transformers follow a set of equations that relate voltage, current, and turns
ratios. The turns ratio determines the voltage transformation between the primary and secondary windings. According to the turns ratio equation, the primary voltage divided by the secondary voltage equals the turns ratio:
Turns ratio = (Primary voltage) / (Secondary voltage) Efficiency, Losses, and Load Considerations:
• Transformers are not perfectly efficient, and energy losses occur during operation. These losses include copper losses in the windings (due to electrical resistance) and core losses (due to hysteresis and eddy currents).
Transformers are designed to minimize these losses and improve overall efficiency.
• Transformer efficiency is defined as the ratio of output power (secondary power) to input power (primary power). Factors such as load conditions, transformer design, and core materials influence efficiency. Transformers
typically operate most efficiently at or near their rated load capacity.
Conclusion:
Understanding the basic principles of transformers is fundamental to
comprehending their operation and importance in the power distribution system.
The principles of electromagnetism, the functioning of primary and secondary
windings, and the relationships between voltage, current, and turns ratios provide
the foundation for the design and operation of distribution transformers.In the next chapter, we will explore the construction and components of distribution transformers in detail. We will delve into the core materials, winding types, insulation systems, and other critical components that contribute to the
efficient and reliable operation of distribution transformers.