What are the specifications and models of transformers? How are specifications and models formulated?

I. classification

According to the cooling mode, they are dry (self-cooling) transformer, oil-immersed (self-cooling) transformer and fluoride (evaporative cooling) transformer.

Classified according to moisture-proof mode: open transformer, encapsulated transformer and sealed transformer.

According to the structure of core or coil: core transformer (insert core, C core, ferrite core), shell transformer (insert core, C core, ferrite core), ring transformer, metal foil transformer.

According to the number of power supply phases: single-phase transformer, three-phase transformer, multi-phase transformer.

Classified by use: power transformer, voltage regulating transformer, audio transformer, intermediate frequency transformer, high frequency transformer, pulse transformer.

2. Characteristic parameters of power transformer

1. Working frequency

Transformer core loss has a great relationship with frequency, so it should be designed and used according to the use frequency, which is called working frequency.

2. rated power

Under the specified frequency and voltage, the transformer can work for a long time without exceeding the output power of the specified temperature rise.

3. rated voltage

The voltage allowed to be applied on the coil of the transformer shall not be greater than the specified value in operation.

4. Voltage Ratio

Refers to the ratio of primary voltage to secondary voltage of transformer. There are differences between no-load voltage ratio and load voltage ratio.

5. No-load Current

When transformer secondary open circuit, the primary still has a certain current, which is called no-load current. The no-load current consists of magnetization current (producing flux) and iron loss current (caused by core loss). For 50Hz power transformer, no-load current is basically equal to magnetization current.

6. No-load Loss

It refers to the power loss measured at the primary stage when the secondary transformer is open. The main loss is the core loss, followed by the loss of no-load current on the primary coil copper resistance (copper loss), which is very small.

7, efficiency

Percentage of the ratio of secondary power P2 to primary power P1. Usually the higher the rated power of transformer, the higher the efficiency.

8. Insulation Resistance

Indicates the insulation performance between transformer coils and between coils and cores. The insulation resistance is related to the performance, temperature and humidity of the insulating materials used.