In today's rapidly evolving technological landscape, transformers have emerged as indispensable components that play a vital role across diverse industries. From power distribution systems to electronic devices, transformers encompass a wide array of types, meticulously engineered to meet evolving and specific requirements.

Whether you're an engineer, technician, or simply someone interested in learning about transformers, you've come to the right place. In this blog, we will explore the world of transformers, discussing their different types, how they work, and their extensive applications in various industries.

Understanding Transformers

A transformer is an electrical device that plays a vital role in the distribution and transmission of electricity. It allows electrical energy to be transferred efficiently from one circuit to another through electromagnetic induction.

Transformers are widely used in electrical power distribution systems. They allow for the efficient transmission of electricity over long distances by stepping up the voltage for reduced losses and then stepping it down again for safe use in homes and businesses. Besides voltage transformation, transformers also provide isolation between the input and output circuits.

They can be found in various sizes and types, ranging from small transformers used in electronic devices to large power transformers found in substations.

How Does a Transformer Work?

A transformer works by utilizing electromagnetic induction to transfer electrical energy between circuits. It consists of two or more coils of wire, known as windings, which are wound around a common magnetic core.

The primary winding, also called the input winding, is connected to the power source or the input circuit. When an alternating current (AC) flows through the primary winding, it generates a magnetic field around the windings and the core. This magnetic field continuously changes in strength and direction due to the alternating current.

The secondary winding, or output winding, is connected to the load or the output circuit. The changing magnetic field induces an electromotive force (EMF) in the secondary winding. This EMF causes an alternating current to flow in the secondary winding, which is then used to power electrical devices or systems.

The core of the transformer plays a crucial role in its operation. It is typically made of a ferromagnetic material such as iron or steel, and provides a closed magnetic circuit, allowing the magnetic flux generated by the primary winding to link with the secondary winding more effectively.

Types of Transformers

Let's explore some common types of transformers: 

Based on Unit

The types of transformers based on the unit depends on the number of phases in the electrical system they are designed to operate with.

Single-Phase Transformers

Single-phase transformers are designed to transfer electrical energy between circuits in single-phase power systems. These transformers consist of a primary winding, a secondary winding, and a laminated iron core.

The primary winding is connected to the input voltage source, while the secondary winding is connected to the load. The primary and secondary windings are magnetically coupled through the iron core.

Applications

Single-phase transformers find application in several areas, including:

  • Power Distribution: Single-phase transformers are commonly employed in residential and commercial buildings. They step down high-voltage power from distribution lines to lower voltages suitable for household and office equipment.
  • Electronics: These transformers are utilized in electronic devices, such as power supplies, to adjust voltage levels according to the requirements of the connected components. They can step up or step down the voltage as needed.
  • Control Systems: Single-phase transformers find applications in control circuits. They provide essential functions such as isolation, impedance matching, and voltage regulation.

Three-Phase Transformers

Three-phase transformers are designed to handle three-phase power systems, which are commonly used in industrial and high-power applications.

These transformers consist of three primary windings and three secondary windings, connected in a variety of configurations, such as Delta (Δ) or Wye (Y) connections.

Applications

Three-phase transformers find application in numerous industries due to their ability to handle higher power loads. Some key applications include:

  • Power Distribution: Three-phase transformers are vital in power plants and substations. They step up the voltage generated by generators for efficient transmission over long distances through power lines.
  • Industrial Applications: These transformers are extensively used in industries to power heavy machinery, motors, and other equipment requiring high electrical power.
  • Electrical Grids: Three-phase transformers facilitate the transformation and distribution of electricity, ensuring a stable and reliable power supply to meet the demands of different users.

Based on Substation

In a substation, transformers play a crucial role in facilitating the efficient and safe delivery of power from high-voltage transmission lines to low-voltage distribution lines. They perform various functions, including voltage conversion, distribution, and protection.

Based on their specific roles within substations, they can be classified into three main types.

Power Transformers

Power transformers are large-sized transformers designed to handle high power levels and step-up or step-down voltage levels to facilitate long-distance transmission of electricity. These transformers typically operate at high voltages ranging from 66 kV (kilovolts) to 765 kV or higher.

They are utilized in various applications, including:

  • Power Generation: Power transformers step-up the voltage generated by power plants to facilitate efficient transmission over long distances.
  • Transmission Substations: These transformers step-down the voltage from transmission lines to a lower level suitable for distribution.
  • Industrial Applications: Power transformers are used in industrial facilities to supply electricity at the required voltage levels for machinery and equipment.

Distribution Transformers

Distribution transformers, also known as service transformers. These transformers operate at lower voltages, typically up to 33 kV, and step-down the voltage received from power transformers to levels suitable for distribution through local networks. Distribution transformers find application in:

  • Powering Residential & Commercial Areas: Distribution transformers supply power to homes, offices, shopping centers, and other commercial establishments, meeting the electrical requirements of lighting, HVAC systems, and electronic devices.
  • Supplying Power to Small Industrial Units: They facilitate the distribution of power to small-scale industrial facilities for operating machinery and equipment.

Instrument Transformers:

Instrument transformers are specialized transformers used for measuring and protecting electrical systems in substations. They are employed in conjunction with instruments and meters to provide accurate readings of voltage and current levels.

Instrument transformers can be further categorized into current transformers (CTs) and voltage transformers (VTs). These transformers serve the following purposes:

  • Metering and Measurement: Instrument transformers enable the precise measurement of high currents and voltages, allowing accurate billing and monitoring of electrical consumption.
  • Protection and Safety: CTs and VTs provide signals to protective relays and devices, ensuring timely detection of faults and the activation of protective mechanisms.
  • Control and Monitoring: Instrument transformers facilitate the monitoring and control of electrical parameters within a substation, allowing operators to maintain system stability and reliability.

Based on Core Design

Cores play a key role in the operation of transformers by providing a path for the magnetic flux generated by the primary winding to induce a voltage in the secondary winding.

Based on the core design, transformers can be broadly categorized into two types:

Core-Type Transformers

Core-type transformers have a core made of laminated iron or steel. The core serves as a magnetic circuit and provides a low reluctance path for the magnetic flux. It consists of a primary winding and a secondary winding wound around the core.

Applications:

Core-type transformers are widely used in:

  • Power Transmission and Distribution: Core-type transformers are extensively used in power transmission and distribution networks to step-up or step-down voltage levels.
  • Electric Grid Infrastructure: Core-type transformers are crucial components in electric grid infrastructure, such as substations and power stations. They facilitate the transformation of voltage levels for efficient power transfer and distribution.

Shell-Type Transformers

Shell-type transformers, also known as core-form transformers, have a core that surrounds the windings. The core is made of a stack of laminations and has a rectangular or circular shape. The primary and secondary windings are placed on either side of the core, with the core providing a path for the magnetic flux.

Applications:

Shell-type transformers find applications in specific scenarios, such as:

  • Instrumentation: Shell-type transformers are commonly used in instrumentation systems where high accuracy and isolation are required. They are used to step down voltage levels and provide electrical isolation for sensitive instruments.
  • Low-Power Applications: Due to their compact size and lower power ratings, shell-type transformers are suitable for low-power applications like audio equipment, small electronic devices, and control circuits.
  • High-Frequency Applications: Shell-type transformers are preferred in high-frequency applications due to their lower losses and improved efficiency. They are commonly used in radio frequency (RF) circuits, telecommunications equipment, and switch-mode power supplies.

Based on Windings

Windings play a crucial role in transferring electrical energy between circuits through electromagnetic induction. They are the conductive coils of wire that are wound around a magnetic core within the transformer. 

Transformers can be classified into two main types based on their windings:

Two-Winding Transformers

Two-winding transformers, also known as conventional transformers, consist of two separate and insulated windings: the primary winding and the secondary winding. The primary winding is connected to the source of electrical power, while the secondary winding is connected to the load. The number of turns in the primary and secondary windings determines the voltage ratio between the input and output of the transformer.

Applications:

  • Power Distribution: Two-winding transformers are extensively used in power distribution systems to step up or step down the voltage levels.
  • Industrial Applications: These transformers are widely employed in various industrial applications to supply power at different voltage levels, depending on the requirements of machinery and equipment.
  • Residential and Commercial Buildings: Two-winding transformers are used to distribute electricity within residential and commercial buildings. They provide the appropriate voltage levels for lighting, heating, air conditioning, and other electrical appliances.

Autotransformers

An autotransformer is a type of transformer that consists of a single winding with taps along its length. The winding has both primary and secondary functions, as it serves as both the input and output winding. The primary and secondary circuits are electrically connected to each other through these taps, resulting in a shared portion of the winding. The voltage ratio in an autotransformer is determined by the ratio of the number of turns between the taps.

Applications:

  • Voltage Regulation: Autotransformers are commonly used for voltage regulation purposes. By varying the tap position, the output voltage can be adjusted to compensate for fluctuations in the input voltage, providing a stable and regulated output.
  • Power Converters: Autotransformers are utilized in power converters to change voltage levels, convert between single-phase and three-phase systems, and adapt to different international standards.
  • Audio Systems: Autotransformers are employed in audio systems, such as amplifiers and mixers, to match impedance between various audio devices. They help in achieving optimal signal transfer and improved audio quality.

Based on Insulation 

Insulation plays a crucial role in electrical transformers by providing protection against electrical leakage and ensuring efficient power transmission. Based on insulation, there are two primary types of transformers:

Dry-Type Transformers

Dry-type transformers, also known as cast resin transformers, utilize solid insulation materials to provide electrical insulation. These transformers are designed to operate without the need for liquid cooling or immersion in oil. Instead, they rely on air circulation for cooling purposes.

Dry-type transformers are widely used in environments where flammability, safety, and environmental concerns are critical factors. They offer several advantages, such as enhanced fire safety, reduced risk of oil leakage, and easier installation and maintenance.

Applications:

  • Hospitals and Healthcare Facilities: These transformers are preferred in medical facilities due to their fire-resistant properties and minimal maintenance requirements.
  • Schools and Educational Institutions: Dry-type transformers are utilized in educational institutions for powering lighting systems, laboratories, and various electrical equipment.
  • Indoor Industrial Applications: They are suitable for indoor installations in industries where flammable or explosive materials are present, such as chemical plants, refineries, and mining operations.

Oil-Immersed Transformers

Oil-immersed transformers, also referred to as liquid-filled transformers, employ oil as the primary insulation and cooling medium. The windings and core of these transformers are immersed in a special insulating oil, typically mineral oil or silicone oil.

Applications:

  • Power Transmission and Distribution Systems: Oil-immersed transformers are extensively used in electrical substations to step up or step down voltage levels for efficient power transmission across long distances.
  • Heavy Industries: Industries such as steel mills, manufacturing plants, and large-scale industrial facilities rely on oil-immersed transformers to handle high-power demands and ensure reliable power supply.
  • Utilities and Power Generation: These transformers are essential components in power generation plants, including thermal power plants, hydroelectric power stations, and nuclear power plants.
  • Renewable Energy Systems: Oil-immersed transformers play a crucial role in connecting renewable energy sources, such as wind farms and solar power plants, to the main grid.

Based on Voltage

Transformers can be categorized into three main types based on the voltage level they operate at:

Low-Voltage Transformers

Low-voltage transformers are designed to handle relatively lower voltage levels, typically ranging from a few volts up to 1,000 volts. These transformers are commonly used in settings where the voltage requirement is relatively low.

Applications:

  • Residential Applications: Low-voltage transformers are used in residential buildings for voltage conversion and distribution of electrical power to various devices and appliances. They provide the necessary voltage levels required for lighting, heating, and other household equipment.
  • Commercial Applications: In commercial settings such as offices, retail stores, and small businesses, low-voltage transformers are utilized to power lighting systems, security systems, and other low-power devices.
  • Industrial Applications: Industries employ low-voltage transformers for powering machinery, equipment, and control systems. They are instrumental in providing appropriate voltage levels to motors, pumps, and other industrial devices.

Medium-Voltage Transformers:

Medium-voltage transformers are designed to handle higher voltage levels, typically ranging from 1,000 volts up to 69,000 volts. These transformers are commonly used in power distribution systems and industrial applications where higher voltages are required.

Applications:

  • Power Distribution: Medium-voltage transformers play a vital role in the transmission and distribution of electrical power from power plants to substations and other distribution points. 
  • Industrial Applications: Medium-voltage transformers find extensive use in heavy industries such as manufacturing plants, refineries, and mining operations.

High-Voltage Transformers:

High-voltage transformers are designed to handle extremely high voltage levels, typically ranging from 69,000 volts and above. These transformers are primarily used in power generation, transmission, and large-scale industrial applications.

Applications:

  • Power Generation: High-voltage transformers are crucial components in power generation plants, where they step up the voltage generated by generators to higher levels for efficient transmission over long distances.
  • Power Transmission: These transformers are employed in electrical substations to step down the high transmission voltages to lower levels suitable for distribution. They ensure safe and reliable power transmission across long distances.
  • Large-scale Industrial Applications: High-voltage transformers are utilized in industries that require exceptionally high power levels, such as steel mills, aluminum smelters, and chemical plants. They provide the necessary voltage levels to operate heavy machinery, induction furnaces, and other power-intensive processes.

Based on Frequency

The frequency refers to the rate at which alternating current (AC) cycles through a complete waveform in a given time period. Based on frequency, transformers can be classified into two main types: 

Low-frequency transformers

Low-frequency transformers are designed to operate at relatively lower frequencies, typically ranging from 50 to 60 Hz. They can transmit electrical energy efficiently over long distances by reducing the losses that occur during transmission.

Applications:

  • Power Transmission: Low-frequency transformers facilitate the transmission of electricity from power plants to substations, where the voltage is then stepped down for distribution to homes, businesses, and industries.
  • Electrical Appliances: Many household appliances, such as refrigerators, air conditioners, and televisions, utilize low-frequency transformers to convert the incoming electrical voltage to a level suitable for their operation.

High-Frequency Transformers

High-frequency transformers are designed to operate at frequencies above the standard 50-60 Hz range. They are commonly used in applications where higher frequencies are required for specialized purposes.

Applications:

  • Power Electronics: High-frequency transformers play a crucial role in power electronic systems, such as inverters and converters. These systems are utilized in renewable energy generation, electric vehicles, and various other advanced power applications.
  • Telecommunications: High-frequency transformers are employed in telecommunication systems to convert electrical signals into different voltage levels for transmission and reception purposes.
  • Switching Power Supplies: High-frequency transformers are an integral part of switching power supplies, which are used in a wide range of electronic devices. These transformers help regulate the voltage and provide efficient power conversion.

Special Transformers for Specific Applications

Special transformers are designed for specific applications that require unique performance characteristics. These transformers are often used in industrial, medical, and military applications. Some examples of special transformers include:

Pulse Transformers

Pulse transformers are an essential component in electrical systems that are used to transfer electrical energy from one circuit to another. They play a crucial role in transmitting pulses of energy while maintaining electrical isolation between input and output circuits.

Pulse transformers are specifically designed to handle short-duration, high-voltage pulses, making them ideal for various applications in electronics, telecommunications, and power systems.

Applications:

    • High-Speed Data Transmission: Pulse transformers are widely used in high-speed data transmission systems, such as Ethernet networks and telecommunications infrastructure. They enable the transmission of digital signals with minimal distortion and provide galvanic isolation, protecting sensitive electronic components from electrical noise and interference.
    • Power over Ethernet (PoE) Systems: PoE technology allows the transmission of power and data over a single Ethernet cable, eliminating the need for separate power cables in devices such as IP cameras, wireless access points, and VoIP phones. Pulse transformers play a crucial role in PoE systems by isolating the power and data circuits, preventing potential electrical hazards and maintaining signal integrity.
  • Pulse Width Modulation (PWM) Control: Pulse transformers help in transmitting PWM signals accurately, allowing precise control of the power delivered to the load. Pulse transformers provide electrical isolation, protecting control circuits from high-voltage switching and reducing the risk of electrical noise affecting the control signals.
  • Radar and Communication Systems: In radar and communication systems, pulse transformers provide impedance matching and galvanic isolation, ensuring efficient power transfer and protecting sensitive components from electrical noise and interference.

SMPS Transformers (Switch-Mode Power Supply Transformers)

SMPS transformers are designed to work in switch-mode power supplies, which convert electrical power from one form to another using high-frequency switching techniques. They are usually smaller in size compared to traditional transformers due to the higher operating frequency.

They typically consist of a primary winding, secondary winding, and sometimes an auxiliary winding. These windings are wound around a magnetic core made of materials like ferrite or powdered iron.

Applications:

    • Consumer Electronics: SMPS transformers are commonly used in consumer electronic devices such as televisions, DVD players, set-top boxes, gaming consoles, and audio amplifiers. Their compact size and high efficiency make them ideal for these devices, where space and power consumption are significant factors.
    • Computer Power Supplies: SMPS transformers are extensively used in computer power supplies to convert the AC input voltage to the DC voltage required by the computer components.
    • Telecommunications: SMPS transformers provide efficient power conversion and are widely used in telecommunications equipment, including routers, switches, modems, and mobile base stations.
  • Renewable Energy Systems: SMPS transformers are increasingly employed in renewable energy systems such as solar inverters and wind turbine power converters. 
  • Aerospace and Defense: SMPS transformers are employed in aerospace and defense applications, including avionics systems, radar equipment, and satellite communication systems. Their compact size, lightweight design, and high efficiency make them useful for these demanding environments.

Current Transformers (CTs)

Current transformers, as the name suggests, are used to measure electric current. They provide a reduced current output proportional to the primary current flowing through them.

Applications:

  • Metering and Billing: CTs are extensively used for accurate current measurement in utility metering applications. They transform high currents into manageable values suitable for measurement by meters, enabling precise billing based on energy consumption.
  • Ground Fault Detection: Current transformers are utilized in ground fault detection systems, which monitor the flow of current from power lines to the ground.
  • Motor Control and Monitoring: In motor control centers (MCCs) and motor protection applications, CTs are employed to measure the currents drawn by motors. This information is used for motor performance monitoring, overload protection, and determining the need for maintenance or troubleshooting.
  • Power Quality Analysis: CTs can be utilized in power quality monitoring systems to measure current harmonics, voltage sags, swells, or transients. By analyzing the captured data, power quality issues can be identified and appropriate corrective measures can be implemented.

Summing Up

From the humble single-phase transformers found in our homes to the powerful high-voltage transformers present in substations, each type plays a crucial role in facilitating the efficient transmission and distribution of electricity.

Therefore, when selecting a transformer for a specific electrical power system, it's important to understand factors like voltage transformation capabilities, working principles, efficiency, and safety requirements associated with each type. This understanding will help ensure the right transformer is chosen to meet the specific needs of the electrical system.