1. Classification of transformers
Classified by cooling method: dry-type (self-cooling) transformer, oil-immersed (self-cooling) transformer, fluoride (evaporative cooling) transformer.
Classification according to moisture-proof method: open transformer, potted transformer, sealed transformer.
Classified by core or coil structure: core-type transformers (blade core, C-type iron core, ferrite core), shell-type transformers (blade core, C-type iron core, ferrite core), Toroidal transformer, metal foil transformer.
Classification 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, medium frequency transformer, high frequency transformer, pulse transformer.
2. Characteristic parameters of power transformer
1. Working frequency
The core loss of the transformer has a great relationship with the frequency, so it should be designed and used according to the frequency of use. This frequency is called the operating 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
Refers to the voltage allowed to be applied to the coil of the transformer, which must not exceed the specified value during operation.
4. Voltage ratio
Refers to the ratio of the primary voltage and the secondary voltage of the transformer. There is a difference between the no-load voltage ratio and the load voltage ratio.
5. No-load current
When the secondary of the transformer is open circuit, there is still a certain current in the primary. This part of the current is called no-load current. The no-load current consists of magnetizing current (generating magnetic flux) and iron loss current (caused by core losses). For a 50Hz power transformer, the no-load current is basically equal to the magnetizing current.
6. No-load loss
Refers to the power loss measured on the primary side of the transformer when the secondary side is open circuit. The main loss is the core loss, followed by the loss (copper loss) caused by the no-load current on the primary coil copper resistance. This part of the loss is very small.
7. Efficiency
Refers to the percentage of the ratio of secondary power P2 to primary power P1. Generally, the greater the power rating of the transformer, the higher the efficiency.
8. Insulation resistance
Indicates the insulation performance between the coils of the transformer and between each coil and the iron core. The insulation resistance is related to the performance of the insulating material used, temperature and humidity.
