We shall take the following two factors into consideration when selecting steel, the one is the machinability of the steel, the other is the vervice character during the processing, we hope the steel has a low strength and high elongation, which make ti easy to cut, stamp or form. But in the service of steel, we hope it has high strength, good impact performance to suffer extreme service condition. For these two reasons, we should select suitable steel form its mechanical properties.  Main Mechanical Properties Include Yield Strength  The yield strength or yield point of a material is defined in engineering and materias science as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its orignal shape whem the applied stress is removed. Once the yield point is passed some fraction of the deformation will be permanent  and non-reversible.  Tensile Strength Tensile strength is indicated by the maximum stress before the break of specimen. In general, it indicates when necking will occur.  Elongation  Elongation , or percent elongation at break, is defined as  the change in gauge length after break per unit of the original gauge length. A high enlongation means the material can stand great permanet deformation before break, or high deformability.   The parameter yield strength, tensile strength, enlongation are measured by tensile test.  Impact Energy Impact energy, or toughness, is determined by the energy absorbed by the specimen during fracture in the impact test. It is measured in units of joules. Impact energy indicates material's resistance to impact load. It is tested by charpy V-notch test.  If welding is required during the process, we should consider the welding performance of the steel.  Welding  For the steel, welding is a fabrication to combine different pieces of steel together. In the welding, normally the binding sites melt together and cool to form a strong joint, such as electric arc welding, gas welding and electric resistance welding.  Weldability Weldability, also known as joinablility, of a material refiers to its alibityy to be welded. Most steels can be welded,but some are easier to weld than others. It greatly influences weld quality and is an important factor in choosing which welding process to use.   

1. Extremely short axial length, saving chassis space.Radial motors are cylindrical in shape, typically increasing power output by extending their length; axial-flux motors resemble "pancakes," allowing for a significantly shorter axial dimension for the same power output. Industry comparisons show that axial-flux motors often achieve an axial length of only about 30%–50% that of radial motors with equivalent power, with some high-performance prototypes being even thinner. 2. Large effective disc area and long lever arm; delivers high torque at low speeds.The axial torque of an axial-flux core depends heavily on the rotor's outer diameter (roughly based on the lever-arm effect of the disk radius); consequently, large-diameter axial-flux designs offer a distinct advantage in torque density at low speeds. For a given volume or outer diameter, an axial-flux core can deliver higher torque than a radial-flux core. 3. Axial-flux cores feature short magnetic paths, relatively low iron losses, and a broad high-efficiency operating range.An axial core follows a straight path across the planar air gap, resulting in a shorter flux path compared to the radial "tooth-yoke-tooth" configuration. When combined with thin silicon steel,concentrated windings, and oil cooling, some designs achieve peak efficiencies exceeding 96%–97% and offer a broader high-efficiency range at low to medium speeds. For electric vehicles, this translates to greater energy savings during city driving, frequent stop-and-go traffic, and regenerative braking. 4. The power output of the axial core can be increased through modular stacking.To increase the power of a radial-flux core, one typically lengthens the core or increases its diameter, but a high length-to-diameter ratio makes the layout difficult; in contrast, an axial-flux core is inherently a flat disc, making coaxial stacking a natural fit.

Scenario 1: New Energy Vehicle Main Drive For high-performance main drive units (800V) in new energy passenger vehicles, 0.2mm non-oriented silicon steel laminations—whether yoke-type or segmented—are recommended. This type of axial core offers advantages such as high saturation torque, low iron losses (due to the thin laminations), compatibility with oil cooling, and cost-effectiveness for mass production.   Scenario 2: Humanoid Robot Joints For the high-performance full-body joints of humanoid robots, axial cores made of ultra-thin silicon steel are recommended.   Scenario 3: eVTOL/Low-altitude Aircraft Operating characteristics: Fundamental frequency of 500–1500 Hz, power density >8 kW/kg, extreme sensitivity to weight, low production volume (hundreds to thousands of units), and high cost tolerance. Therefore, an axial core made of 0.1 mm thin silicon steel is recommended, as it offers a favorable thrust-to-weight ratio and the market for ultra-thin silicon steel is relatively mature.   Scenario 4: Industrial Servo / High-Speed Spindle For general-purpose servo applications (medium speed), axial cores made of 0.2–0.35 mm silicon steel laminations are recommended, as this technology is mature and offers a favorable cost-performance ratio. For high-speed spindle applications (>20,000 rpm), we recommend using amorphous/nanocrystalline axial cores, as controlling iron loss is critical in such scenarios. For applications involving frequent servo start-stop operations, an axial core made of 0.2 mm thin silicon steel is recommended due to its advantages of low inertia and low iron loss.   Scenario 5: White Goods / Air Conditioner Compressors Operating characteristics: fundamental frequency of 50–200 Hz, low torque density, extremely high production volume (100,000 to over a million units), and extreme cost sensitivity. Therefore, an axial iron core made of 0.35mm non-oriented silicon steel—characterized by low frequency, high volume, and cost-efficiency—in either wound or stamped form is sufficient. However, the high-speed motors found in some high-end vacuum cleaners and hair dryers can also utilize axial cores made from thin (0.2 mm) silicon steel laminations, offering certain advantages during high-frequency operation.

The application of axial cores is primarily concentrated in scenarios with an extreme pursuit of "thinness, lightness, and high torque density." Its essence is a flat electromagnetic conversion core, so wherever there is a need to "make the motor flat, light, and powerful," it will be found.   Currently, the more mature and cutting-edge applications are mainly concentrated in the following areas: 1. New Energy Vehicles: In-Wheel Motors and Main Drive Motors This is currently the most watched and imaginative application scenario.   In-Wheel Motors: The motor is directly inserted into the wheel. The flat shape of the axial core perfectly fits the limited space inside the wheel, and its inherent high torque characteristics allow it to directly drive the wheel, eliminating the need for a reducer and differential. Mercedes-Benz, Ford, GM, BYD, Dongfeng, and other automakers have related in-wheel motor concept cars or mass production plans, with the axial core being the core component. Hybrid/Pure Electric Main Drive: Some high-end models are beginning to use axial flux motors as auxiliary drive on the front or rear axle. Due to its extremely short length, it can be easily placed between the engine and transmission, or nestled in a chassis gap, without occupying valuable cabin space.   2. Joint Motors for Humanoid Robots Humanoid robot joints require extremely high power and torque density, while maintaining a very compact size. Traditional radial motors are often too long, protruding outside the joint and affecting aesthetics and flexibility. Axial motors, with their flattened shape, can be perfectly integrated into the joints of robot arms and legs, like a "muscle package." Many are researching or already using axial iron-core motors to achieve more natural movements and greater explosive power.   3.Industrial Automation and Machine Tools: High-Speed Spindles and Servo Motors High-Speed Spindles: Axial cores, due to their short magnetic circuits and low iron losses, are ideal for high-frequency, high-speed rotating spindles. For example, the spindles of PCB drilling machines and engraving machines can reach speeds of tens of thousands or even hundreds of thousands of revolutions per minute (RPM). Axial cores effectively reduce heat generation and energy loss. Servo Motors: In automated equipment requiring rapid start-stop and precise positioning (such as the seventh axis of a robot and packaging machinery), the low inertia of axial motors allows for extremely fast response times, making them more suitable than traditional radial servos.   4.Home Appliances & Consumer Electronics Air Conditioner Compressors: Some high-end Japanese air conditioners are beginning to use axial core motors in their inverter compressors. Its flat structure allows for a shorter overall compressor profile, making it easier to integrate into ceiling or wall-mounted units.   Vacuum Cleaners & Hair Dryers: While radial structures are the mainstream for high-speed digital motors from some high-end brands, axial solutions are under research. Axial motors allow for shorter overall lengths, making them more comfortable to hold, while maintaining high suction power.   Drones/Flying Cars (eVTOL): For electric vertical takeoff and landing (eVTOL) aircraft, every gram of weight is critical. The high power density and lightweight advantages of axial core motors are amplified here, and many eVTOL projects utilize axial topology for their propeller motors.

From a process perspective, the core difference between Oil-immersed transformers and Dry-type transformers lies in the construction method of the insulation system and the winding encapsulation process. Simply put: oil-immersed transformers achieve insulation and heat dissipation by being "immersed in oil," while dry-type transformers achieve insulation by being "encapsulated with solid materials." 1.Insulation system construction process (the most crucial difference)Oil-immersed transformersThe windings are "barely wound": copper wire is wrapped with cable paper or corrugated paper, and is not fully encapsulated after winding. Insulation is filled with oil: all gaps between the windings and the core, between the windings, and between the windings and the tank are filled with insulating oil. Key process: Vacuum oil injection—After the transformer body is dried, filtered and degassed insulating oil is injected under vacuum to ensure that the oil completely wets all insulation gaps and removes air bubbles. Dry-type transformers (taking the mainstream epoxy resin casting type as an example) The windings are "solidified": after the copper wire is wound, it is placed in a mold, and epoxy resin is poured under vacuum. After curing, it forms a hard insulating entity. Insulation relies on epoxy resin: the resin itself is both an insulating material and a structural support. Key process: Vacuum casting—the epoxy resin is mixed with curing agent and filler under vacuum and then injected into the mold to eliminate air bubbles and ensure that the insulation layer is dense and defect-free. 2.Winding Manufacturing Process： Oil-Immersed Transformer No overall encapsulation after winding Interlayer insulation is done with cable paper, and the ends are insulated with insulating cardboard or laminated wood. The wound coil is directly fitted onto the iron core, and then the entire coil is immersed in oil. Dry-Type Transformer Vacuum casting or vacuum pressure impregnation (VPI) is mandatory after winding. Low-voltage coils are mostly wound with copper or aluminum foil to reduce eddy current losses. High-voltage coils use enameled round or flat wire, and are then cast with epoxy resin. After casting, curing treatment (temperature curing) is required to allow the resin to reach its final strength.   3.Assembly and Sealing Process： Oil-Immersed Transformer After the transformer body (core + windings) is assembled, it must be installed in a sealed oil tank. The oil tank welding requirements are strict, and leak testing (air pressure or water pressure test) is required. Installation accessories: oil conservator, radiator, gas relay, dehumidifier, etc. Finally, vacuum oil filling is performed. Dry-Type Transformer After the transformer body is assembled, an oil tank is not required. The protective outer shell (metal plate or mesh cover) is installed directly, mainly for protection rather than sealing. Temperature control probe and cooling fan (optional) are installed. No oil conservator, no radiator, no gas relay   4.Testing Procedures： Oil-Immersed Transformers In addition to routine electrical tests, oil hydration tests are required (breakdown voltage, water content, acid value, chromatographic analysis, etc.). A sealing test is required (to check for tank leakage). Partial discharge measurements are usually performed after oil filling. Dry-Type Transformers No oil hydration test required. Focus on partial discharge levels (typically ≤10pC, advanced European level ≤5pC). Insulation resistance and absorption ratio tests are required to check for moisture.

In Africa, the demand for oil-immersed and dry-type water treatment systems differs significantly—oil-immersed systems overwhelmingly dominate in terms of quantity, while dry-type systems represent a niche growth driver characterized by "small scale and high growth rate." They are not competing in the same arena, but rather serving entirely different scenarios. In terms of unit quantity, the African transformer market is characterized by "Oil-immersed transformers being the majority".   l Why is there a much greater demand for oil-immersed containers in Africa? Africa's natural environment and socioeconomic conditions are almost tailor-made for Oil-immersed transformers: 1. Adaptability to extreme high-temperature environments: Temperatures in Africa (especially North Africa, the Sahel, and the Gulf region) often exceed 50°C. Oil-immersed transformers use insulating oil as their cooling medium, and their thermal management system remains stable at high temperatures; Dry-type transformers rely on air convection for heat dissipation, which significantly reduces their efficiency in high-temperature environments. This is the core physical reason why Oil-immersed transformers dominate in North Africa, the Sahel, and the Gulf region. 2. Outdoor Scenarios Dominate Africa's electricity demand primarily comes from: Rural electrification (outdoor pole-mounted/ground-mounted transformers)、Mining microgrids (open-pit mines)、 Distributed photovoltaic power stations Urban power grid expansion (outdoor box-type transformers). Over 90% of these scenarios are outdoors, and Oil-immersed transformers outperform Dry-type transformers in terms of cost-effectiveness, strong overload capacity, and weather resistance. 3. Cost Sensitivity Standard oil-immersed distribution transformers cost approximately $15-30/kVA, while Dry-type transformers cost $30-50/kVA, more than double the price. In most African countries and projects with tight budgets, Oil-immersed transformers are preferred over Dry-type transformers whenever possible. 4. Technological Maturity and Ease of Maintenance In Africa, there is a shortage of local skilled workers. Oil-immersed systems are mature equipment with globally applicable inspection and maintenance systems. Dry systems, on the other hand, require more technical expertise from maintenance personnel should problems occur.   However, with the increase in urbanization rates in Africa, the accelerated construction of data centers in South Africa, Nigeria, and Kenya, and the development of commercial real estate, the proportion of dry-type roofing will continue to climb from the current penetration rate of ~17%, and is expected to reach 30%+ in the commercial building sector around 2030. Even so, in terms of unit numbers, the overwhelming advantage of oil-immersed roofing in Africa is unlikely to be shaken in the next 10-15 years.

From the perspective of raw materials, the fundamental difference between Dry-type transformers and Oil-immersed transformers lies in the different insulating media and winding encapsulation materials, which determines the composition of their entire material system.   Core insulation medium: oil or air + solid insulation Oil-immersed transformer Main insulation material: Mineral insulating oil (refined from petroleum fractions, such as naphthenic oil and paraffinic oil The insulating oil performs two main functions: electrical insulation and heat dissipation. The oil fills all gaps between windings, between windings and the core, and between windings and the tank. Dry-type transformers Main insulation material: Solid insulation system, no liquid insulation used Three common technical approaches: Epoxy resin casting type (mainstream): Windings are vacuum-cast and wrapped with epoxy resin Nomex paper insulation type (H-class Dry-type transformers): DuPont aromatic polyamide paper + air Glass fiber impregnation type: Glass fiber reinforced resin Heat dissipation relies entirely on air convection (AN) or forced fan blowing (AF)   Core Material: Basically the same Both cores use cold-rolled grain-oriented silicon steel sheets (CRGO), processed by stacking or winding. There is no fundamental difference in this raw material. Some high-end Dry-type transformers use amorphous alloy cores to reduce no-load losses, but this is not a dividing line between product categories.   Differences in materials between fuel tank and structural components Oil-immersed transformer Oil tank: Welded steel plate, inner surface coated with insulating varnish Accessories: Oil conservator, radiator/cooling pipes, gas relay, explosion-proof pipe, desiccant (silicone filter), oil filter valve These components are themselves important raw material components. Dry-type transformer Enclosure: Protective enclosure made of aluminum alloy or steel plate (IP20/IP23), no oil tank No oil conservator, no radiator, no gas relay Only a temperature control system (PT100 sensor + temperature controller) and cooling fan (optional) Overall material usage is significantly less than that of oil-fired transformers   Oil-fired transformers rely on "oil" for insulation and heat dissipation, so the windings can be bare and the oil tank must be thick and heavy; dry-fired transformers rely on "epoxy resin sealing" for insulation and "air" for heat dissipation, so the overall materials are lighter and cleaner, but the cost of epoxy materials themselves is not low.

Compared to oil-immersed transformers, Dry-type transformers have significant advantages in four core dimensions: fire safety, flexible installation, environmental friendliness and maintenance-free operation, and suitability for special environments.   1. Intrinsically Safe: Oil-free, Non-flammable, and Non-explosive No flammable liquids: Dry-type transformer windings are directly insulated with epoxy resin or NOMEX paper, eliminating the risk of leakage, combustion, or explosion. Zero Firefighting Burden: No need for emergency oil tanks, sump pits, sprinkler systems, or firewalls; can be directly installed in buildings, basements, shopping malls, hospitals, data centers, subway stations, and other densely populated areas. In the event of a fire in an oil-immersed transformer, the oil will spread, burn, and release toxic fumes; Dry-type transformers completely avoid this.   2. Extremely Flexible Installation Location Can be installed close to the load center: Dry-dry transformers can be placed in the middle of a floor, inside a shaft, or in a corner of the machine room, without requiring a separate transformer room (provided ventilation is sufficient). Unrestricted by height/number of floors: Oil-cooled transformers are generally only installed on the ground floor or one basement level (considering oil tank and transportation), while dry-dry transformers can be installed on the roof or equipment floor of high-rise buildings. Small footprint: Without oil tankers, radiators, oil conservators, gas relays, and other accessories, the structure is compact.   3. Simple Operation and Maintenance, No Leakage Risk Oil-Free Handling: No need for regular oil sample filtering, oil breakdown voltage testing, oil level replenishment, or leak repair. No Seal Aging Issues: Oil-lubricated transformers are most susceptible to leaks due to aging gaskets; Dry-type transformers completely eliminate this problem. Routine Inspections Only Require Checking the Temperature Controller and Fan; Almost No Consumables Required.   4. Environmental Protection and Cleanliness No Oil Pollution: Even after dismantling, there is no waste oil disposal issue, and copper and silicon steel sheets are recycled more cleanly. No Odor or Oil Vapor Emissions: Suitable for air-sensitive environments such as food factories, pharmaceutical workshops, and precision electronics cleanrooms.   5. Strong Short-Circuit Resistance (Under Certain Structures) The windings of resin-cast Dry-type transformers are integrally cured, resulting in extremely high mechanical strength. Their ability to withstand short-circuit electrodynamic forces is superior to that of hydraulic transformers of the same capacity (hydraulic transformer windings are loose and secured by pressure pins). In industrial and mining power distribution systems subjected to frequent short-circuit impacts, Dry-type transformers often have a lower failure rate.   6. Controllable Partial Discharge Level The vacuum casting process can control partial discharge to a very low level (≤5 pC), and its tolerance to high-frequency harmonics and operating overvoltages is better than that of oil-cooled transformers (partial discharge in oil-cooled transformers tends to increase with the deterioration of oil quality).

Compared to Dry-type transformers, Oil-immersed transformers offer significant advantages primarily in capacity and voltage rating, heat dissipation and overload protection, operating efficiency, procurement costs, and environmental adaptability.   Larger capacities and voltage levels are possible. Oil-immersed transformers rely on oil circulation for insulation and heat dissipation, eliminating the resin/air bottleneck of dry-type transformers. Therefore: Single unit capacity: Dry-type transformers typically reach 2500-3150 kVA as the mainstream upper limit, while Oil-immersed transformers can easily reach tens or even hundreds of MVA. Voltage levels: Dry-type transformers commonly reach 35 kV, while Oil-immersed transformers can reach 110 kV, 220 kV, and even higher, making them the mainstay of power transmission and distribution networks. In short: For large-capacity, high-voltage applications, Oil-immersed transformers are almost the only option. Strong heat dissipation and overload capacity Transformer oil has a much higher specific heat capacity and thermal conductivity than air. Combined with oil convection/forced oil circulation, it can quickly dissipate heat from the windings. Short-term overload capacity is significantly stronger than dry-type transformers (higher thermal inertia, more easily withstands impact loads). During long-term high load rate operation (≥75%), winding temperature rise control is more stable, and it is less likely to be forced to shut down or derating by temperature management strategies.   Superior operating efficiency (especially under high load conditions) Lower Pk (load loss) at actual operating temperatures: oil cooling ensures uniform temperature distribution, and winding resistance doesn't spike with localized hot spots like in dry-type systems. In scenarios with prolonged high loads and long operating times, oil-cooled transformers typically offer lower overall losses (electricity costs) than dry-type systems. Furthermore, the amorphous alloy oil-cooled transformer route allows for extremely low Po (no-load loss), making it a crucial option for achieving "ultimate efficiency," while dry-type amorphous transformers are limited by heat dissipation constraints, resulting in a much narrower application range. Lower Procurement Costs for the Same Capacity For the same capacity, the price of hydraulic substations is generally significantly lower than that of dry-type substations. The larger the capacity, the more substantial the absolute price difference. For large-capacity substations (e.g., ≥1600 kVA), there are fewer dry-type models to choose from, while hydraulic substations offer a wider selection, mature competition, and superior cost-effectiveness.   Lower operating noise Oil dampens vibrations in the core and windings, and combined with the inherent buffering effect of outdoor/panel-mounted substations, oil-cooled substations typically operate 5-10 dB quieter than dry-type substations. In noise-sensitive environments, oil-cooled substations are actually more suitable.   Enhanced environmental adaptability (outdoor-oriented) Good weather resistance: Unaffected by low temperatures (oil won't freeze and crack), and can withstand high temperatures thanks to its heat dissipation design; wider temperature range than dry-type systems. For outdoor platforms, transformer substations, mountainous areas, and rural power grids—scenarios where there is "no one to manage the environment and the conditions are harsh"—oil-type systems are more robust.

1. No-load loss Po – basically at the same level Po mainly depends on the core material and the design magnetic flux density. For the same efficiency class, Oil-immersed transformers and Dry-type transformers use the same level of cold-rolled grain-oriented silicon steel sheets (CRGO) or even amorphous alloys, so Po can be very close. 2. Load Loss Pk – Oil-immersed transformers have an advantage at "actual operating temperature" This is the key point of divergence: Oil-immersed: Winding heat is quickly carried away by the oil, resulting in uniform oil temperature and more controlled hot spot temperatures. Resistance temperature rise is relatively controllable ⇒ R(T) in Pk = I²R(T) won't spike too high. Dry-immersed (epoxy resin cast SCB): Although F-class (155℃)/H-class (180℃) insulation materials allow for higher temperatures, for lifespan management, the control system usually keeps the winding temperature within a more conservative range (e.g., ≤120~130℃ long-term). Once it approaches the threshold, it will limit the load or force the fan to stop running at full speed. Result: With the same conductor quantity and design margin, the Pk of an oil-immersed transformer is more likely to stabilize at a lower effective value during long-term high-load operation – this is not due to "different copper wires," but rather a more powerful heat sink. 3. Heat dissipation determines a hidden efficiency factor: "Available Overload Efficiency". This means that if your load characteristics are consistently high (>75%), the overall operating efficiency curve of a hydraulic transformer will look better and be more durable than that of a dry-type transformer. Conversely, if the load rate fluctuates at a low to medium level year-round, the efficiency difference between the two will be minimized.   In short, efficiency isn't a difference in label between oil-immersed and Dry-type transformers, but rather a difference in the matching of operating conditions. Oil-immersed transformers excel in "lower overall losses and larger thermal margins under high load rates and long operating times"; Dry-type transformers excel in "maintenance-free operation, cleanliness, safety, and comparable efficiency under reasonable load rates (avoiding pushing the limits). What truly drags down efficiency is never the type itself, but rather—two mismatches: overloading (powering up a small load while the transformer is underutilized) or underloading (overheating and limiting the load capacity).

The selection of Dry-type Transformers based on application scenarios revolves around their "oil-free and fireproof" safety characteristics, while also comprehensively considering factors such as heat dissipation methods, protection levels, and insulation materials. Core Selection Dimensions 1.Insulation Types: Epoxy Resin Cast Type: The windings are completely encapsulated in epoxy resin, providing excellent moisture, dust, and corrosion resistance. It is maintenance-free, has low noise, and is the mainstream choice.Unencapsulated/Winding Type: The windings are impregnated with insulating varnish, resulting in better heat dissipation and slightly stronger overload capacity. However, its moisture and dust resistance is weaker, and it is often used in specific industrial environments. 2.Protection Rating (IP Code): IP20: Standard protection, prevents finger contact with live parts, suitable for clean, dry dedicated electrical rooms. IP23: Protects against water droplets within a 60° vertical angle, suitable for general factory buildings, semi-outdoor environments, etc.   3.Cooling Methods: Natural Air Cooling (AN): Relies on air convection, suitable for applications with smaller capacity or lower load rates. Forced Air Cooling (AF): Utilizes a fan, increasing the transformer's short-term overload capacity by 40-50%, suitable for applications with large load fluctuations and periodic overload requirements. Summary of selection steps： 1. Determine safety and location: Confirm whether dry systems are necessary (e.g., indoors, in densely populated areas). This is a prerequisite.2. Insulation type: For most scenarios (buildings, public facilities), epoxy resin casting (SCB) is preferred; non-encapsulated (SGB) can only be considered in industrial workshops with extremely high heat dissipation requirements and clean environments. 3. Protection rating: IP20 for cleanroom electrical distribution rooms; IP23 for factories with slight moisture or dust; IP54 and above for outdoor or extreme environments. 4. Cooling method: Select natural cooling (AN) when the load is stable; if the load fluctuates or requires short-term overload, forced air cooling (AF) must be installed. 5. Specific requirements: Whether on-load tap changer, low noise, high insulation class (H class) or explosion-proof function is required.

The key to selecting an Oil-Immersed transformer based on the application scenario is balancing safety, environment, cost, and performance. The following are selection guidelines for different scenarios:   1. Conventional Outdoor Substations / Regional Power Distribution Scenario Characteristics: High capacity demand, high voltage level, and high heat dissipation requirements. Preferred Type: Non-enclosed or Energy-efficient enclosed type Reason: Ample outdoor space and good heat dissipation. High-efficiency energy-saving models are preferred, although the purchase price is slightly higher, the long-term electricity cost savings are significant, resulting in a lower total lifespan cost.   2. Industrial and Mining Enterprises (General Environment) Scenario Characteristics: Load may fluctuate, requiring stable power supply; environment may contain dust but is not highly corrosive. Preferred Type: Enclosed type or fully sealed type. Reason: The enclosed structure effectively prevents dust and moisture, extending maintenance intervals. If voltage fluctuations within the workshop are large, affecting equipment operation, an on-load tap changer type should be selected to stabilize the voltage.   3. Harsh/Hazardous Environments such as Petroleum, Chemical, and Mining Industries Scenario Characteristics: Flammable and explosive gases, high dust levels, high humidity, or corrosive substances are present. Preferred Type: Fully sealed type or explosion-proof special transformers. Reason: The fully sealed structure eliminates contact between oil and air, preventing aging of the insulating oil and the ingress of external flammable gases. It must meet the explosion-proof requirements of the location; this is a safety red line.   4. Agricultural Irrigation and Rural Power Grid Scenario Characteristics: Dispersed load, large seasonal fluctuations, limited maintenance conditions, and cost sensitivity. Preferred Type: Economical non-enclosed type or basic enclosed type Reason: To control initial investment while meeting basic needs. Enclosed type reduces maintenance workload and is more suitable for unattended field operations.   5. Locations with extremely high power quality requirements Scenario characteristics: Data centers, precision manufacturing facilities, hospitals, laboratories, etc., requiring extremely stable voltage. Preferred type: On-load tap-changing sealed transformer Reason: On-load tap-changing function can adjust the output voltage in real time when the load changes, ensuring power quality and protecting precision equipment.