Transformer is to transform AC voltage, current and impedance device, when the primary coil with alternating current, the core (or cores) will be generated in the exchange of flux, the secondary coil induces a voltage (or current). Transformer from the core (or core) and the coils, there are two or more coil windings, in which power supply is called the primary coil winding, the other is called the secondary coil winding.

First, the classification by cooling Category: Dry (from cold) transformer oil (from cold) transformer, fluoride (evaporative cooling) transformer. Moisture-proof manner by Category: Open-type transformers, potting transformers, enclosed transformers. Sort by core or coil structure: core-type transformers (Insert core, C-type core, ferrite core), shell-type transformer (plug-chip core, C-type core, ferrite core), ring-type transformer, metal foil transformers. Press the power phases Category: single-phase transformers, three phase transformers, multi-phase transformer. By Type: Power transformers, regulating transformers, audio transformers, intermediate frequency transformers, high frequency transformers, pulse transformers.

Second, SG Single / three phase dry type transformer parameters;
1. Frequency - frequency of the transformer core loss and a great relationship, it should be used to design and use of frequency, this frequency of said operating frequency.
2. Rated Power - provides frequency and voltage, the transformer can be long-term work, not exceeding the prescribed temperature rise of output power.
3. Rated voltage - is allowed on the transformer winding voltage is applied, the work is not greater than the specified value.
4. Voltage ratio - means the transformer primary voltage and secondary voltage ratio, a load voltage and load voltage ratio than the differences.
5. No load current - the transformer secondary open, the primary is still a certain current, this part of the current called no-load current. No-load current from magnetizing current (flux generated) and the iron loss currents (caused by the core loss) component. 50Hz power transformer, the load current is essentially equal to the magnetizing current.
6. Load loss - refers to the transformer secondary open, the primary measure power loss. The main loss is the core loss, followed by the no-load current is generated on the primary coil copper resistance loss (copper loss), this part of the loss is small.
7. Efficiency - refers to the secondary power P1 P2 and the ratio of the percentage of primary power. Usually the larger the rated power transformer, the higher the efficiency.
8. Insulation resistance. That the coil transformer, the insulation between coil and core. Insulation resistance level of performance with the use of insulating materials, temperature and moisture level of the degree.