- Published Aug 13, 2025
- Last Modified Aug 13, 2025
- 5 min
What Are Electrical Transformers?
Whether isolating a current or decreasing or increasing a voltage, there is a transformer for every need.
Reviewed by Mithun Subbaroybhat, Technical Support Engineer (August 2025)
Transformers are seen nearly wherever there is an electrical circuit, from power grids to office computers. But what is the function of a transformer, how do they work, and are there different types?
What Do Electrical Transformers Do?
Electrical transformers are essential components in the Philippines' power distribution system, often called passive electrical devices. They play a crucial role in transferring electrical currents between circuits. Whether it’s distributing electricity from power plants or powering households and businesses, transformers adjust voltage levels to suit specific needs.
These devices can increase (step-up) or decrease (step-down) voltage, making them vital for a wide range of applications, from small household appliances to large industrial machinery. Transformers enable efficient and safe power transmission across the archipelago’s various terrains and help support the growing demand for electricity in urban and rural areas alike.
How Do Electrical Transformers Work?
Transformers operate based on Faraday’s Law of Electromagnetic Induction. Simply put, they connect two electrical circuits without a direct electrical connection by using a magnetic field, enabling the transfer of current while maintaining the same frequency.
A transformer typically consists of three main parts: a magnetic core, a primary winding, and a secondary winding. Picture the core as a square or rectangular iron core, with coils of wire (windings) wrapped around opposite sides. When an alternating current flows through the primary coil, it creates a magnetic field in the core, which induces a voltage in the secondary coil. This process transfers electrical energy from the primary circuit to the secondary circuit, either stepping the voltage up or down, depending on the winding ratios.
In the Philippines, this principle is key to supporting the country’s power grid, which requires stepping up voltage for long-distance transmission and stepping it down for safe residential and commercial use.
What Does a Step-Up Transformer Do?
A step-up transformer increases voltage from a lower level to a higher level. For example, power plants in the Philippines use step-up transformers to raise the voltage of electricity generated before it travels across long distances via transmission lines. This helps prevent energy loss, which is crucial given the archipelago’s geography of islands and varied terrain.
In operation, a step-up transformer has fewer turns of wire around the primary coil and more turns around the secondary coil, boosting the voltage at the output side. While voltage increases, the current decreases proportionally, but the frequency remains unchanged which is important for consistent power quality.
What Does a Step-Down Transformer Do?
Conversely, a step-down transformer reduces voltage from a higher level to a safer, lower voltage suitable for homes and businesses. For instance, once electricity reaches distribution substations in urban centers like Quezon City, Davao, or Cebu, step-down transformers lower the high transmission voltages to levels that can be safely used by consumers.
Step-down transformers have more turns in the primary coil than the secondary, allowing them to reduce voltage while increasing current. These transformers are sometimes called autotransformers and are essential for powering household appliances, lighting, and electronics safely across the Philippines.
Electrical Transformer Types
As well as coming in different sizes, transformers can come in different types, to suit energy needs.
Voltage Transformer (Potential Transformer)
Voltage transformers, also known as potential transformers, are commonly used by power companies to monitor and regulate electricity voltage across the grid. They reduce high voltages to measurable levels, ensuring accurate readings and safe system operations.
Power Transformer
Power transformers are usually large, stationary devices found at power plants or substations. These step-up or step-down transformers handle very high voltages and are key to transmitting electricity across cities. Due to their size and heat generation, many require cooling systems, often using oil or air for heat dissipation.
Air Core Transformer
Used in some specialized electronics or smaller equipment, air core transformers do not have a metal core. Instead, the windings are wrapped around materials like plastics, using air as the magnetic medium. These types are less common in large power setups but are found in smaller devices.
PCB Transformer
PCB (Printed Circuit Board) transformers are integral to electronics manufacturing here in the Philippines, especially for gadgets and computer-based products made in local tech hubs. These transformers isolate current and adjust voltage levels within circuit boards, ensuring component safety.
More Transformer Types
Where Are Electrical Transformers Used?
Transformers have diverse applications, from powering urban infrastructure to enabling electricity access in remote areas. They’re found in household devices like doorbells and electric fans, as well as in industrial machines and power plants.
On a macro scale, transformers ensure that electricity generated from geothermal plants, hydroelectric facilities, or coal power plants efficiently reach homes and businesses across the islands.
They also stabilize and isolate electrical currents, measure circuit voltages accurately, balance power loads, and, most importantly, ensure safety by reducing dangerous voltages to manageable levels. Given the Philippines’ unique geography and growing energy demands, transformers are indispensable for strengthening the national grid and supporting sustainable energy initiatives.
