Types of Distribution and Power Transformers

9 May 2023

What is a Transformer?

Transformers are devices that transfer energy from one circuit to another through electromagnetic induction. In other words, they are devices used to reduce or increase the voltage and current of any alternating current (AC) without changing its frequency by the desired amount. The abbreviated form of the transformer is “trafo.” Transformers are electrical machines that, based on the principle of electromagnetic induction, convert electrical energy from one or more circuits into different voltage and current values at the same frequency.

Distribution Transformers and Their Characteristics

Distribution transformers are transformer devices that lower the voltage of electrical energy, making it suitable for distribution to consumers.

Where and for What Purpose Are They Used?

The primary purpose of transformers is to adjust current and voltage levels according to the need, making electrical energy suitable for consumption or transmission. Distribution transformers, specifically, lower the voltage for distribution and deliver electrical energy to consumers at the required voltage and current levels. Distribution transformers reduce the voltage to match consumer needs (e.g., 11 kV, 6.6 kV, 3.3 kV, 440 V, 220 V).

Distribution transformers are commonly used in factories, hospitals, homes, and other locations. Factories and hospitals with high electricity consumption have dedicated distribution transformers for their use. In contrast, homes and places with relatively lower electricity consumption may share a single distribution transformer.

Distribution transformers with a capacity of S ≤ 400 kVA are mounted on poles, while those with S > 400 kVA are installed in transformer substations.

Distribution transformers are typically step-down transformers.

Types of Distribution Transformers:

  1. Oil-Immersed Transformers
  2. Hermetically Sealed Transformers
  3. Dry-Type Transformers (Epoxy Resin-Encapsulated)

Materials Used in Production:

Distribution transformers are categorized by cooling type, and common materials used in these types include the main tank containing magnetic cores and windings, magnetic iron cores for magnetic flux circulation, voltage tap changers to adjust voltage levels (YG-AG), and arc horns to prevent damage to insulation material due to high-voltage discharge. The primary winding consists of fine wire conductors, while the secondary winding uses thick wire conductors.

What Is a Power Transformer and Its Types?

Power transformers are devices that change the magnitude of electrical energy without altering its frequency. These transformers are used to adjust voltage levels in electrical energy transmission and distribution. Power transformers are produced using laminated silicon steel sheets and feature insulated windings. When alternating current is applied to one winding, it generates a time-varying magnetic flux that induces voltage in the other winding. The ratio between the number of turns in the primary and secondary windings determines the voltage transformation between the input and output circuits.

Technical Specifications of Power Transformers

Power transformers have a power range of 2.5 MVA to 25 MVA with different power ratings. The voltage range is between 20 kV and 36 kV. They come in 1 or 3-phase options with various tap positions. Tap changes can be made under no-load and load conditions. Power transformers can have ONAN or ONAF cooling systems and can be used in both indoor and outdoor settings. Copper is the preferred conductor type based on customer needs. Models with porcelain insulators, side terminals, and cable boxes are typically chosen with expansion chambers. Radiator groups are used as cooling equipment. Different models with varying protection equipment are available based on usage and location.

Transformers are used for the following purposes:

  1. To reduce or increase voltage or current.
  2. To provide impedance matching.
  3. To protect multiple circuits connected to the same power line from short circuits that may occur in case of reverse connections.

Materials Used in Production:

Materials commonly used in the production of distribution transformers vary based on cooling type. In general, they include the main tank containing magnetic cores and windings, a magnetic core made of silicon steel for magnetic flux circulation, a voltage tap changer to adjust the YG-AG level, an arc horn to prevent damage to the insulation material from high-voltage discharge, and input (primary) windings consisting of fine wire conductors and output (secondary) windings consisting of thick wire conductors.