3 Essential Knowledge Points About Transformers: Guide to Understanding Transformers

A transformer is a stationary electrical device used to change alternating voltage and current levels while transmitting AC power. It operates on the principle of electromagnetic induction, facilitating the transfer of electrical energy between circuits. Based on their applications, transformers can be categorized into power transformers, testing transformers, instrument transformers, and special-purpose transformers:

• Power Transformers: Essential for power transmission and distribution in power grids and for end-users.
• Testing Transformers: Used to perform dielectric strength (voltage-withstand) tests on electrical equipment.
• Instrument Transformers: Serve as measurement and protection devices in power systems, such as potential transformers (PTs) and current transformers (CTs).
• Special-Purpose Transformers: Include electric furnace transformers for smelting, welding transformers, rectifier transformers for electrolysis, and small adjustable transformers.

Power Transformer Operation: Power transformers are stationary electrical apparatus that convert one value of alternating voltage (or current) into another or several values of the same frequency. When the primary winding is supplied with AC, it generates a varying magnetic flux. This flux, guided by the iron core, induces an alternating electromotive force (EMF) in the secondary winding. The magnitude of the induced EMF in the secondary winding is proportional to the number of turns in the windings, meaning the voltage is directly related to the turns ratio.

The primary function of a transformer is to transmit electrical energy, making its rated capacity one of the most important parameters. Rated capacity is a conventional expression of power, indicating the amount of electrical energy that can be transmitted, measured in kVA or MVA. When a transformer is subjected to its rated voltage, this parameter determines the rated current that can be carried under specified conditions without exceeding the temperature rise limit.

Energy-Efficient Transformers: Non-crystalline alloy core distribution transformers are known for their energy efficiency, particularly due to their exceptionally low no-load losses. Ensuring the lowest possible no-load loss is a central consideration during the design process. When designing the product structure, it's crucial not only to protect the non-crystalline alloy core from external forces but also to accurately and reasonably select the material's characteristic parameters.

Importance in Power Systems: Power transformers are one of the main pieces of equipment in power plants and substations. They play a multifaceted role by stepping up the voltage to efficiently transmit electricity over long distances and stepping down the voltage to various levels suitable for different uses. Both voltage elevation and reduction must be accomplished using transformers.

During the transmission of electrical energy in power systems, there are inevitable losses in both voltage and power. Voltage losses are inversely proportional to the voltage level, while power losses are inversely proportional to the square of the voltage. By using transformers to increase the voltage, the transmission losses are reduced.

Transformer Construction and Installation: A transformer consists of two or more windings wound around a common iron core, connected through a varying magnetic field according to the principle of electromagnetic induction. The installation location of a transformer should consider ease of operation, maintenance, and transportation, as well as safety and reliability.

Proper Capacity Selection: When using a transformer, it's essential to choose the appropriate rated capacity. During no-load operation, transformers require significant reactive power, which must be supplied by the power system. If the transformer's capacity is oversized, it increases initial investment and results in the transformer operating at no-load or light load for extended periods, increasing the proportion of no-load losses, lowering the power factor, and increasing network losses, leading to uneconomical and inefficient operation. Conversely, if the transformer's capacity is undersized, it may lead to prolonged overload operation, potentially damaging the equipment. Therefore, the rated capacity of a transformer should be selected based on the actual load requirements, avoiding both oversizing and undersizing.

By understanding these 20 fundamental aspects of transformers, you can better appreciate their critical role in modern power systems and the importance of proper selection and application.

【 Classification of Transformers 】

Transformers can be categorized into various types based on their applications and construction. The main classifications include:

• Distribution Transformers: Used to step down the voltage from transmission levels to distribution levels for end-user consumption.
• Power Transformers: Essential for stepping up or stepping down voltages in power transmission and distribution networks, serving as a critical link between power plants and consumers.
• Fully Sealed Transformers: Designed to prevent moisture and contaminants from entering, offering enhanced durability and reliability.
• Pad-Mounted Transformers (Composite Transformers): Integrated units that combine the transformer with protective devices, typically installed in outdoor environments.
• Dry-Type Transformers: Utilize air for cooling and are suitable for indoor applications where fire safety is a priority. They are known for their clean operation, energy efficiency, and low maintenance requirements.
• Oil-Immersed Transformers: Use mineral oil for cooling and insulation, commonly used in outdoor applications. They offer higher efficiency and longer service life but require stringent maintenance and environmental precautions.
• Single-Phase Transformers: Designed for single-phase AC systems, often used in residential and light commercial applications.
• Furnace Transformers: Specialized for use in electric arc furnaces for smelting processes.
• Rectifier Transformers: Convert AC to DC by providing the necessary voltage levels for rectification, used in electrolysis and other industrial processes.
• Reactors (Chokes): Devices used to provide inductance, helping to control current flow and filter out harmonics.
• Interference-Suppressing Transformers: Designed to reduce electromagnetic interference (EMI) in electrical systems, ensuring cleaner power quality.
• Lightning Protection Transformers: Equipped with features to protect against surges caused by lightning strikes.
• Transformer Units (Pad-Mounted): Compact, all-in-one units that include the transformer and associated switchgear, typically used in outdoor installations.
• Testing Transformers: Used for conducting high-voltage tests on electrical equipment to ensure their dielectric strength.
• Corner-Tap Transformers: Feature additional tapping points to allow for fine-tuning of output voltage.
• High-Current Transformers: Designed to handle very high currents, often used in special applications such as welding or testing.
• Excitation Transformers: Provide the necessary excitation voltage for synchronous generators and other rotating machines. 

【 Components of a Transformer】

A transformer primarily consists of the following components:

• Core: The magnetic core provides a path for the magnetic flux and is typically made of laminated silicon steel to minimize eddy current losses.
• Windings (Coils): The primary and secondary windings are wound around the core. The number of turns in each winding determines the voltage transformation ratio.
• Tank (Oil Tank for Oil-Immersed Transformers): Houses the core and windings, providing mechanical support and protection. For oil-immersed transformers, the tank also contains the cooling oil.
• Conservator (Oil Pillow): An auxiliary reservoir that compensates for changes in oil volume due to temperature variations, maintaining the oil level within the tank.
• Insulating Bushings: Provide electrical insulation for the high-voltage and low-voltage terminals, allowing them to pass through the tank wall safely.
• Tap Changer: Allows for adjustments in the voltage output by changing the number of turns in the windings, either on-load or off-load.

【Primary Functions of a Transformer】

The primary role of a transformer is to transform electrical energy by either increasing (stepping up) or decreasing (stepping down) the voltage level while maintaining the same frequency. This capability is crucial for efficient power transmission and distribution:

In summary, both step-up and step-down transformations are essential functions performed by transformers, ensuring that electrical energy can be efficiently transmitted and distributed to meet the diverse needs of various users.