Working Principle:

Dry type transformers use the principle of electromagnetic induction to transmit electrical energy or signals from one circuit to another. When AC current passes through the primary coil (i.e. the primary winding), alternating magnetic flux is generated in the iron core. Since the primary and secondary windings are on the same iron core, when the magnetic flux passes through the secondary winding (i.e. the secondary winding), induced electromotive force is generated on the secondary side of the transformer, thereby achieving voltage conversion. The output voltage is determined by the ratio of the turns of the primary coil and the secondary coil.

Structural composition:

Iron core: The iron core is the magnetic circuit part of the transformer, usually made of high-quality cold-rolled grain oriented silicon steel sheets stacked together. The silicon steel sheets use 45 degree fully oblique joints, allowing magnetic flux to pass along the direction of the silicon steel sheet joints, which can reduce eddy current losses and improve the efficiency of the transformer. To prevent rusting and insulation of the iron core, a layer of insulating paint will be applied to the surface of the iron core.

Winding: The winding is the circuit part of a transformer used to transmit electrical energy. The winding of dry-type transformers is usually made of copper or aluminum wire, and can be divided into various types according to different insulation methods and structural forms. Common winding forms include winding type, epoxy resin and quartz sand filled casting type, glass fiber reinforced epoxy resin casting type (i.e. thin insulation structure), multi strand glass fiber impregnated epoxy resin winding type, etc.

Insulation system: As dry-type transformers do not have insulation oil as the insulation medium, other insulation materials need to be used to ensure the insulation performance between windings and between windings and iron cores. Common insulation materials include epoxy resin, Nomex paper, etc. Epoxy resin has good insulation properties, mechanical strength, and heat resistance, and is widely used in the insulation packaging of dry-type transformers; Nomex paper is a high-performance insulation material with excellent heat resistance, flame retardancy, and insulation properties, commonly used in H-grade dry-type transformers.

Temperature control system: In order to ensure the safe operation of dry-type transformers, a comprehensive temperature detection and protection system is usually equipped. The system monitors the temperature of the transformer in real time through temperature control probes embedded inside the winding, and transmits the temperature signal to the temperature controller. When the temperature exceeds the set value, the thermostat will automatically start the fan for heat dissipation, or issue signals such as alarm and trip to protect the transformer.

Shell: The shell serves to protect the internal components of the transformer and also has a certain level of protection, which can prevent external dust, moisture, and other impurities from entering the interior of the transformer. The material of the shell is generally stainless steel or steel plate. Depending on the usage environment, different protection levels can be selected, such as IP20, IP30, IP43, IP54, etc.

Classification:

Resin dry-type transformer: high mechanical strength, strong short-circuit resistance, good moisture and corrosion resistance, small partial discharge, long operating life, low loss, strong overload capacity.

Immersion dry-type transformer: With high insulation and heat resistance, it has better fire resistance and does not produce a large amount of smoke during high-temperature combustion.

Advantages:

High safety performance: No use of insulating oil, no risk of fire or explosion, and no release of toxic gases, harmless to the environment and human health.

Good fire resistance: It has the characteristic of being difficult to ignite and self extinguishing, suitable for places with high fire prevention requirements.

Low maintenance workload: There is no need to monitor and maintain the insulation oil during operation, reducing maintenance workload and costs.

High operational efficiency: low losses, significant energy-saving effects, and can improve the operational efficiency of the power system.

Small size and light weight: easy to install and transport, can be installed at the center of the load, does not require special foundations, saves floor space and installation costs.

Strong adaptability to the environment: able to operate in high humidity and harsh environments, with good moisture and dust resistance.

Low noise: The noise generated during operation is relatively small, and the impact on the surrounding environment is minimal.

Disadvantages:

High cost: Compared with oil immersed transformers, dry-type transformers have higher manufacturing costs, so their prices are relatively expensive.

Poor heat dissipation performance: relying on air convection for cooling, the heat dissipation effect is not as good as oil immersed transformers, and the overload capacity is relatively weak.

High environmental requirements: Although it has strong adaptability to the environment, it may still affect its normal operation in some extremely harsh environments, such as places with strong corrosive gases and a large amount of metal shavings.

Application scenarios:

High rise buildings: Due to their high requirements for fire prevention and limited space, dry-type transformers have the characteristics of small volume and good fire resistance, making them an ideal choice for high-rise building power distribution systems.

Subway, airport, theater and other public places: These places are densely populated and have extremely high safety requirements. The safety performance of dry-type transformers can meet the needs of these places.

Industrial enterprises: In some industrial enterprises with high environmental requirements, such as electronics factories, pharmaceutical factories, etc., dry-type transformers can avoid insulation oil pollution to products.

In the field of new energy, such as photovoltaic power generation, wind power generation and other new energy generation systems, dry-type transformers have also been widely used.