The classifications of power transformer

1. By function:

Power transformers are divided into two categories: step-up transformers and step-down transformers. Step-down transformers are used in factory substations. The step-down transformer of the terminal substation is also called the distribution transformer.

2. By capacity:

Power transformers are classified according to capacity series, and there are two types of R8 capacity series and R10 capacity series.

R8 capacity series means that the capacity level is increased by multiples of R8≈1.33. China’s old transformer capacity levels use this series, such as: 100kvA, 135kvA, 180kvA, 240kvA, 320kvA, 420kvA, 560kvA, 750kvA, 1000kvA, etc.

R10 capacity series refers to the capacity level is increased by multiples of R10 ≈ 1.26. The capacity class of the R10 series is relatively dense and convenient for reasonable selection. It is recommended by the IEC (International Electrotechnical Commission). China’s new transformer capacity classes use this series, such as: 100KVA, 125kvA, 160kvA, 200kvA, 250kvA, 315kvA, 400kvA, 500kvA, 630kvA, 800kvA, 1000kvA.

3. By the number of phases:

Power transformers are divided into two types: single-phase and three-phase. Factory substations usually use three-phase power transformers.

4. By the pressure regulation method:

Power transformers are divided into two types: voltage regulation with load (also called voltage regulation without excitation) and voltage regulation with load. Most substations in factories use no-load voltage-regulating transformers.

5. According to the winding structure:

Power transformers are divided into winding structures, including single-winding autotransformers, double-winding transformers, and three-winding transformers. Most transformer substations use double-winding transformers.

6. Classification by winding insulation and cooling method:

Power transformers are divided into winding insulation and cooling methods, including oil-immersed, dry and inflatable (SF6). Oil-immersed transformers include oil-immersed self-cooled, oil-immersed air-cooled, oil-immersed water-cooled, and forced oil circulation cooling. Most of the substations in factories use oil-immersed self-cooled transformers.

The so-called gas-filled transformer refers to a transformer in which the magnetic circuit (core) and windings of the transformer are located in a shell filled with insulating gas. In the past, SF6 gas was generally used, so it is also called gas insulated transformer

7. According to winding conductor material:

Power transformers are classified according to the winding conductor material, and there are two types of copper winding transformers and aluminum winding transformers. Factory transformer substations mostly used aluminum winding transformers, but low-loss copper winding transformers are now more and more widely used.