Electricity comprises two essential components: current and voltage.

• Current represents the flow rate of electrical energy, measured in amps.

• Voltage denotes the force of that electrical energy, measured in volts.

Visualize electricity akin to water flowing through a pipe.

• Current mirrors the rate of water flow.

• Voltage equates to the water pressure.

To transport water from the city reservoir to various destinations, a substantial pipe and considerable water pressure are essential. City water lines are constructed to accommodate massive water volumes, swiftly propelled by robust water pressure.

Now, envisage connecting a high-volume, high-pressure city water pipe directly to your kitchen sink. The faucet would burst upon activation, resulting in a torrent flooding your home. For usability, water pressure from the main line must be moderated using pressure regulators.

Transformers perform a parallel role in managing electricity. Electricity flowing through power lines can surpass 300,000 volts—an immense “electrical pressure.” Transformers render electricity usable by decreasing the voltage at the point of use, known as step-down transformers.

These transformers vary from sizable substation transformers in utility substation yards to prominent green padmount transformers adjacent to businesses, to smaller pole-mount transformers atop power poles.

Commercial and industrial operations employ large transformers, providing three-phase voltages such as 480 or 208 volts. Conversely, homes and small businesses utilize smaller single-phase transformers for 120/240v single-phase power. Our focus here centers on three-phase distribution transformers.

How Transformers Operate?

Transformers adhere to the fundamental law of energy conservation, asserting that energy cannot be created nor destroyed, only transformed. Hence, transformers do not generate electricity; their role is to alter voltage to align with the user’s requirements.

This voltage modification is achieved through the principle of electromagnetic induction.

Electromagnetic Induction

When an alternating electric current courses through a conductor, it engenders an imperceptible yet dynamic magnetic field around the electrified conductor. Introducing a second conductor into this evolving magnetic field results in the generation of current within the second conductor, courtesy of the moving flux lines in the field.

Leveraging electromagnetic induction, voltage can be either increased or decreased between the two conductors by configuring them into coils. One coil, with more loops, experiences electrification, inducing a current in the second coil with fewer loops at a lower voltage compared to the first coil. This ingenious process allows transformers to adeptly adjust voltage levels, catering precisely to the diverse needs of users.

Bushings

Transformer bushings serve as insulated terminals facilitating the safe passage of electricity through the transformer tank wall without establishing direct electrical contact. These components play a crucial role in connecting the transformer to the power source on the high voltage side and linking to the load on the low voltage side.

Core & Coils

The transformer’s core and coils, positioned at its core, are pivotal in the induction process. As electricity travels from the power line to the transformer, the coils govern the transformation of incoming voltage. These coils, crafted from either aluminum or copper, are intricately wound around the core. This dynamic interplay between the core and coils lies at the heart of the transformer’s functionality.

Load Break Switches

A load break switch (LBOR switch) for transformers is a unique rotary switch enabling electrical workers to manually disconnect the transformer from the power grid, effectively de-energizing the core and coils. Termed load break switches, these switches hold the capability to be employed even when the transformer is energized and operational, commonly referred to as being “under load.”

Fuses

Transformer fuses protect the electrical system in case there’s a problem with the transformer or in the equipment further down the electrical stream. When exposed to a dangerously high current or excessive heat, a thin wire (called an “element”) within the fuse melts. This opens or “breaks” the flow of electricity, disconnecting the transformer from the power grid.

Voltage Adjustment Taps

The voltage adjustment taps on a transformer enable the adjustment of secondary voltage to ensure accuracy when the primary voltage deviates from the expected range, whether higher or lower. The tap setting is modified by manipulating the tap changer. As the tap changer rotates, it disengages small sections of the primary windings, thereby adjusting the ratio of primary to secondary windings. This adjustment effectively lowers the primary voltage rating to maintain the desired secondary voltage.

Fluid

Transformer oil or fluid serves the crucial role of cooling transformers as they generate heat during operation. A designated tank is filled with this specialized fluid to ensure temperature control. The fluid circulates through channels or “ducts” situated between the transformer’s windings, functioning as both an insulator and a cooling medium. It’s important to note that only liquid-filled transformers incorporate transformer fluid in their design.

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