Transformers are essential electrical devices that play a crucial role in the transmission, distribution, and utilisation of power. They are designed to “transform” electrical energy from one voltage level to another. This makes it possible for electricity to efficiently flow over long distances and deliver it at suitable voltages for various applications.
From powering our businesses to supporting industrial machinery and infrastructure, transformers act as the backbone of electrical systems, ensuring a reliable and safe electricity supply. That’s why it is important to know your transformers, learn how many types of transformers are available, and then make an informed decision that is best suited to meet your business needs.
Types of Transformers Based on the Core Design
A transformer is categorised into three types, based on the arrangement of the windings around its core.
1. Core-Type Transformer
This type of transformer features a frame composed of two cylinders and two horizontal bars. The magnetic core takes on a square shape, forming a unified magnetic circuit. The cylindrical coils for the high-voltage (HV) and low-voltage (LV) circuits are positioned on the two cylinders.
2. Shell-Type Transformer
The shell-type transformer consists of a central cylinder and two outer cylinders. Both the HV and LV coils are located on a central column. This transformer incorporates a dual magnetic circuit.
3. Berry-Type Transformer
The magnetic circuit of this transformer resembles a wheel. A sturdy metal shell securely encases the transformer, and it is filled with oil internally.
Types of Transformers Based on Voltage Conversion
1. Step-Up Transformer
2. Step-Down Transformer
A step-down voltage transformer, as the name suggests, reduces the output voltage. In other words, it converts high voltage, low current power into low voltage, high current power. For instance, a power supply may have a voltage of 230-110V, while a doorbell only requires 16V. Therefore, it is advisable to utilise a step-down transformer to decrease the voltage from 110V or 220V to 16V.
In many regions, voltage is reduced to 440V/230V for safety purposes, which necessitates a lower number of turns on the secondary winding compared to the primary winding. Consequently, a reduced voltage is generated at the output (secondary) end of the transformer.
Types of Transformers Based on Purpose
1. Power Transformer
Power transformers are primarily employed in high-voltage transmission networks. There are many types of power transformers. These are rated at levels such as 400kV, 200kV, 110kV, 66kV, and 33kV, with many having ratings exceeding 200 MVA. These transformers are installed at generating stations and transmission substations requiring high-capacity transformers. Power transformers are designed for maximum efficiency, reaching 100%, and are larger in size compared to distribution transformers.
Due to the high voltage generated, power cannot be directly distributed to consumers. Therefore, a step-down power transformer is used to reduce voltage to the desired level. These transformers operate at partial load, leading to core losses throughout the day while copper losses depend on the load cycle of the distribution network.
When connected to the transmission network, power transformers experience significantly less load fluctuation compared to direct connection to consumers. However, if connected to the distribution network, load fluctuations are more prevalent. Power transformers operate for 24 hours at transmission stations, resulting in core and copper losses occurring throughout the day. These are cost-effective for power generation at low voltage levels. Raising the voltage level reduces the current in the power transformer, resulting in lower I2R losses but increased voltage regulation.
2. Distribution Transformer
A distribution transformer, also known as a consumption transformer, serves the purpose of stepping down voltage from a medium-voltage source to the voltage required for residential and industrial appliances. Designed to reduce voltage for distribution to end-users for commercial purposes, these transformers offer good voltage regulation and operate efficiently at 50% load for 24 hours.
3. Isolation Transformer
Isolation transformers feature independent primary and secondary windings, with a magnetic flux relationship connecting them. Unlike autotransformers, isolation transformers have separate primary and secondary windings linked only through a magnetic field. This configuration ensures electrical independence and defines the key characteristics of an isolation transformer:
- Any point on the secondary coil has zero voltage relative to the ground, providing safety against electrical shocks.
- Voltage varies between different points of the secondary winding, reducing the risk of electrical leakage in device housings and enhancing user safety.
- Each primary or secondary winding possesses different volt-ampere characteristics based on the turns ratio in their respective sections
