Power Transformers: Understanding Its Types, Working Principles & Features

The electrical management world uses various transformers. Among these, the most important ones are the power transformers. They are widely used in multiple industries to step up and down voltages. However, even after being widely used, you might not be aware of what power transformers are. To help you with this, we have a comprehensive guide explaining everything necessary about these transformers. So, start reading below to unveil the details. 

What are Power Transformers?

What are power transformers? Do you often look for an answer to this question? Your search ends now. These transformers are electrical devices that transfer electrical energy between varying voltage levels in an electrical power grid. There are two primary functions of power transformers. It steps up or increases the electricity voltage at the electrical power generating station. These transformers also step down or decrease electricity voltage at the electrical power distribution station. These functions of a power transformer facilitate efficient transmission and distribution of electrical energy over a long distance. 

The electricity generated at power plants in power grids typically has high current and low voltage. Therefore, to minimise the energy loss during transmission over long distances, the high and low-voltage electricity is transformed into high and low currents. A step-up power transformer is used for this. On the other hand, a step-down power transformer transforms electricity into low-voltage electricity to make it safer for use in homes, industries and businesses. We will explain both types of power transformers in detail later in this guide. 

Power transformers play a significant role in maintaining the efficiency and stability of power distribution systems. These devices help reduce energy loss, ensure safe electricity delivery to end users, and enhance voltage regulation. They are used for various applications, ranging from smaller distribution points to large substations. Therefore, they are an integral part of the modern electrical infrastructure. 

Power Transformer Working Principle

Power transformers work on the principle of electromagnetic induction, which was discovered by Michael Faraday. The principle states that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil. A power transformer contains two main components: primary and secondary windings. These coils of wire are wound around a common iron core. 

A changing magnetic field is generated in the iron core when an alternating current flows through the primary winding. This alternating magnetic field results in an alternating voltage in the secondary winding. This induced voltage depends on the turn ratio of the windings. If the turns are more in the secondary than the primary winding, the transformer increases the voltage. On the other hand, if the secondary winding has fewer turns than the primary winding, the transformer steps down the voltage. The role of the core in a transformer is to efficiently transfer the magnetic flux between the windings with minimal energy loss. 

Power Transformer Specifications

• Rated Power- 3 MVA to 200 MVA
• Typical Primary Voltages- 11, 22, 33, 66, 90, 132, 220 kV
• Typical Secondary Voltages- 3.3, 6.6, 11, 33, 66, 132 kV
• Phases- Single or three-phase transformers
• Rated Frequency- 50 or 60 Hz
• Cooling Type- Oil Forced Air Forced Cooling
• Installations- Outdoor or Indoor
• Tapping - On-load or off-load tap changers

Power Transformer Applications

Some typical applications of power transformers are as follows. 

• Power transformers are used to reduce power losses during electric power transmission.
• They are used in electric power distribution and generation. 
• These transformers are preferred in cases where the load requirement is at total capacity 24x7. 
• Power transformers are used in high voltage step-up and step-down.

Construction of Power Transformers

Power transformers have the following components. 

• Steel Tank (Body)
• Core
• Coil Winding
• Conservator
• Breather
• Thermometer
• Vent Pipe
• Valves
• Buchholz Relay
• Tap Changing Switch

Types of Power Transformer

• Step-up and step-down Transformers: These transformers alter the voltage of an AC supply. A step-up transformer increases voltage with many more turns in the secondary winding than in the main winding. Alternatively, a step-down transformer decreases voltage with fewer turns in the secondary winding compared to the main winding.

• Single-phase and Three-phase Transformers: Single-phase transformers, which have one primary and one secondary winding, are used for single-phase AC supplies. Three-phase transformers, which are used for three-phase AC supplies, have three primary windings and three secondary windings hooked up in a star or delta configuration. These are ideal for manufacturing uses and big power systems.

• Two-winding and Autotransformers: Two-winding transformers have different primary and secondary windings, perfect for excessive voltage ratios (greater than two). Autotransformers, with individual winding serving both secondary and primary circuits, are more effective for lower voltage ratios (less than two) and economical for many uses.

• Distribution and Power Transformers: Distribution transformers step down voltage for regional distribution to businesses and homes, operating close to total load with effective voltage regulation. Power transformers, utilised in transmission networks to step up and step down voltage between generating substations and stations, handle varying voltages and big power transfers.

• Instrument Transformers: These are special transformers employed for measuring high currents and voltages. These transformers reduce higher currents to a lower, measurable value, while prospective transformers (PT) reduce higher voltages for measurement by standard instruments, ensuring accuracy and safety.

• Oil-cooled and Dry type Transformers: Oil-cooled transformers work with mineral oil for cooling spreading through radiators or heat exchangers, which is ideal for high-power applications. Dry-type transformers utilise air for cooling, facilitated by fans or vents, and are generally used inside or perhaps in locations where fire safety is an issue.

Read More:- WHAT ARE THE DIFFERENT FUNCTIONS OF ISOLATION TRANSFORMERS AND SURGE PROTECTIVE DEVICES

Wrapping Up

What are power transformers? Yes, we know you can now answer this question very well. But do you know the right place to buy these transformers? Yes, you guessed it right. Shop online from Schneider eShop for the best quality, durability, and convenience. 

Frequently Asked Questions

Q1. How to Maintain Power Transformers?

Ans: Maintaining power transformers is essential for their optimum performance and long lifespan. You must regularly inspect, test and service them regularly to ensure reliable functioning. Tightening connections, replacing insulating oil, cleaning cooling systems and conducting electrical tests are some of the many steps to maintain power transformers. 

Q2. What are the Common Causes Behind Failure of Power Transformer?

Ans: Common causes behind the failure of a power transformer are as follows. 

• Contamination of insulating oil
• Overheating
• Mechanical damage
• Overloading
• Electrical surges
• Insulation breakdown

Q3. How to Measure the Efficiency of a Power Transformer?

Ans: The efficiency of a power transformer is measured with the following formula-

Efficiency = (Output Power / Input Power) × 100%

It is measured by comparing the output and input power.