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.   

Radial motor cores are laminated steel structures inside electric motors. They carry magnetic flux radially, in and out from the shaft. Their main job is guiding flux across the air gap to produce torque efficiently in radial flux motors.   Here, "radial" describes the direction of the magnetic flux crossing the air-gap: perpendicular to the shaft. It does not refer to radial internal combustion engines, a common mix-up. Think of these cores as the motor's magnetic highway. You will find them in most mainstream motors today.   Key Takeaways Radial motor cores use thin steel sheets to guide magnetic flux and produce torque efficiently. Thinner sheets reduce energy losses but cost more to make, so choose thickness based on your motor's needs. Radial flux motors are common and cost-effective, while axial flux motors offer higher power density for specific uses. Check stacking quality carefully: measure the bore and stacking factor to avoid efficiency losses. Match the core design and steel grade to your application for the best performance and cost.   Radial Motor Cores Defined Construction Basics A radial motor core is a stack of thin steel sheets. Each sheet is called a lamination. You stamp each lamination as a full ring, then stack the rings along the shaft in a straight vertical column. This build forms the stator and rotor magnetic circuits in a radial flux motor. The stack gives flux a low-reluctance path through the machine.   Stacking direction matters. The steel grain and the insulation coating run in the plane of each sheet. Flux travels within that plane, so the stack carries magnetic flux along the intended route instead of across the sheet edges. Rotational registration between slots is the main alignment task during stacking. A slight twist between rings can shift the slot pattern and disturb the air gap field.   Thickness is a design choice. Ruixin Mould lists common lamination thickness for radial flux motor cores at 0.35 mm to 0.5 mm. Thinner sheets cut eddy-current losses. Thicker sheets cost less to stamp and handle. You balance the two against the efficiency target of the motor.   Components and Materials The usual material is non-grain-oriented electrical steel. "Non-grain-oriented" means the steel has similar magnetic properties in every direction within the sheet plane. That suits a radial design, where flux spreads in many directions around the ring. Grain-oriented steel, by contrast, performs best along one rolling direction.   A radial stator core and a radial flux motor core share the same basic build. Both use stacked cylindrical steel laminations cut from coated sheet. The coating insulates each sheet from its neighbor and blocks current from flowing between them. Laminated iron cores therefore run cooler than solid steel parts under the same magnetic load.   SHUNZHISHEN TECHNOLOGY supplies laminated core steel for these builds. You can source electrical steel laminations in the grade and thickness your design calls for, then stamp and stack them to the drawing.   The table below summarizes the standard build details for this motor topology. Attribute Radial Flux Motor Cores Stacking method Laminations stamped as full rings, stacked along the shaft in a straight vertical column; alignment mainly controls rotational registration between slots Common lamination thickness 0.35 mm to 0.5 mm These cores serve most electric motors in daily use. The next section explains how flux moves through them to make torque.   How Radial Flux Motors Work Magnetic Flux Paths Start with the magnets. They push flux outward across the air gap to the teeth. The flux then runs along the back iron and returns across the air gap to another rotor pole. EMWorks describes this magnetic flux path in radial flux machines as considerably longer than in axial machines, and it spans three stages: From one rotor pole to the first tooth Through the back iron to the second tooth Back to another rotor pole   Each circuit crosses the air gap twice. That gap is the weakest link in the magnetic circuit, so a small air-gap error costs real torque. Reluctance rises sharply as the gap widens, and the field spreads sideways near the slot openings. The radial direction — perpendicular to the shaft — defines this motor topology. You can trace the electromagnetic flux by eye: out from the rotor, across the gap, along the back iron, and back again. A short return path keeps reluctance low. A long one forces you to spend more copper and more steel for the same output. Pole count changes the pattern but not the rule. Each pole pair repeats the same loop around the bore.   Lamination Design and Stacking Thin laminations fight eddy currents. A changing magnetic field induces small circulating currents in steel. Each insulated sheet breaks that loop, so magnetic losses stay low. Sheet thickness sets the trade. Thinner sheets cut losses and raise stamping cost. Stack the sheets along the shaft axis, and flux stays in the plane of each sheet. A radial flux motor core relies on this rule, and so does a radial stator core. Any radial motor core you stack follows the same logic. Rotate a sheet out of line, and the path bends at the joint.   Stacking direction also sets the air-gap profile. A straight column keeps the bore round. A tilted stack shifts the bore and opens the air-gap on one side. Check registration between slots as you build. Then measure the finished bore before you press the core into the housing.   Builders join the sheets in several ways. Interlocking dimples save fixtures but add a small local short. Welds along the outside diameter hold a stack firmly and suit high-volume lines. Cleats and rivets work well for short runs. Whichever method you pick, watch burr height and coating damage. A burr bridges two sheets and creates a current path. Stress relief annealing after stamping restores the steel's properties near cut edges. Stacking factor tells you how much of the stack is really steel. Tight stacking raises it. Loose stacking leaves gaps that behave like extra air.   This layout suits most motor designs. Its long route costs some material. In exchange, you get a simple round bore, easy winding, and proven manufacturing. Those traits explain why this layout dominates mainstream motor production. Apply these electromagnetic principles and you can predict where a design will lose motor efficiency before you cut steel. Match the core type and the steel grade to the duty cycle, and the design will hold up.   Radial Flux Motor vs. Axial Radial Flux Direction The difference starts with flux orientation. In a radial flux motor, magnetic flux crosses the air gap perpendicular to the shaft. In an axial design, flux runs parallel to the shaft axis. Boating Mag puts it plainly: the flux acts in parallel—axial—with the axis of the shaft. Stanford Magnets summarizes both paths in the table below. Motor Type Magnetic Flux Direction Radial flux motor Flux moves radially outward from the rotor center toward the stator, or radially inward; perpendicular to the axis Axial flux motor Flux is aligned parallel to the axis of rotation   A third option, the transverse flux topology, routes flux in yet another pattern. Each motor topology trades simplicity against density. Axial machines often use electrical steel in wound or other forms rather than typical laminated stacks, so their core supply chain differs from a radial stator core build.   Performance and Cost Axial designs push density higher. Turntide reports axial flux motors can reach up to four times the torque and power density of equivalent radial machines, with up to 50% less motor weight and IE4-class efficiency. Beyond Motors cites 30–40% higher torque density and roughly 10 kW/kg power density for a yokeless architecture. Radial flux permanent magnet motors remain the baseline for good reason: their windings sit in a proven, scalable format.   Cost tells the other side. PatSnap notes radial flux motors benefit from decades of manufacturing optimization and high-volume economies of scale. Axial builds need specialized tooling and tight tolerances, which Tech Briefs says limits volume production and raises unit costs. Regulatory compliance applies to both: electromagnetic compatibility and safety standards shape design and can add compliance costs, according to a LinkedIn market outlook. Match the topology to your duty cycle, not to a headline number.   Applications and Sourcing Where Radial Cores Fit Best You will find radial motor cores in the mainstream of electric motors. Leili Motor lists electric vehicles, household appliances, pumps and compressors, and industrial automation as common homes for this design. A conveyor line that values cost and uptime often runs a radial flux induction motor. The cylindrical casing also cools easily with airflow, so fan-based cooling suits industrial settings. Leili Motor expects radial flux machines to stay the standard in industry, thanks to low cost, simplicity, and availability.   Sourcing Checklist Start with steel grade. Non-oriented electrical steel is the isotropic default for radial flux traction motors, while grain-oriented steel appears in niche segmented stators. Standard lamination thickness runs from 0.35 mm to 0.5 mm. Thinner laminations cut eddy-current loss, which matters at higher frequencies. Check stack perpendicularity too; precision work typically holds within 0.1 mm per 50 mm of stack height. Criterion What to Check Steel grade Non-oriented steel for most radial designs Thickness 0.35–0.5 mm standard; thinner for high frequency Stacking factor At least 0.92 per IEC 60404-8-8 Tolerances Stack perpendicularity near 0.1 mm per 50 mm Supplier capability Bonded stacks, tooling lead time, traceability Ask suppliers for core loss testing on sample stacks. Confirm they can ship bonded, pre-assembled stacks and hold tooling lead times under eight weeks, as Strategic Market Research reports many OEMs now require. SHUNZHISHEN TECHNOLOGY serves as a sourcing resource for laminated core steel in the grade and thickness your design needs.   Radial motor cores are laminated steel structures. They guide magnetic flux radially across the air gap to produce torque. Lamination design sits at the center of motor efficiency, so sheet thickness and stacking quality deserve your attention early.   Radial flux motors suit most mainstream applications. Axial motors fit specific high-power-density niches. Neither wins everywhere, so weigh duty cycle and volume before you choose.   Match core type and steel grade to your application. Check the flux path, the air-gap tolerance, and the loss target together. SHUNZHISHEN TECHNOLOGY offers laminated core steel as a sourcing resource when you specify radial motor cores for your next build.   FAQ What makes a radial motor core different from a solid steel part? A solid steel part lets current circulate freely inside the metal. A radial motor core uses thin, coated sheets instead. Each sheet blocks those circulating currents, so the core runs cooler and wastes less energy. You get the same magnetic path with far lower losses. Why does lamination thickness matter so much? Thinner sheets cut eddy-current losses, and that gain grows at higher frequencies. Standard thickness runs from 0.35 mm to 0.5 mm. At higher frequencies, you should move toward thinner grades. Balance the loss savings against the higher stamping cost before you commit. How do I check stacking quality before assembly? Measure the finished bore and confirm the stack stands perpendicular. Precision work typically holds within 0.1 mm per 50 mm of stack height. Check the stacking factor too; IEC 60404-8-8 sets a minimum of 0.92 for uncoated steel. Loose stacks behave like extra air in the gap. Can I use one core design across several products? Sometimes, but the duty cycle decides. A radial flux motor core tuned for a pump may lose efficiency in a high-speed traction drive. Match steel grade, sheet thickness, and slot pattern to each application. Reusing a proven radial stator core saves tooling cost when the duty cycles align. Which motor topology should I pick for a tight space? Space and volume drive the answer. A radial flux design gives you a simple round bore, easy winding, and proven manufacturing at scale. An axial design packs more power into less weight, yet it needs specialized tooling. Weigh your production volume against the density target.

A radial flux motor core contains five main components: the stator core, the rotor core, the windings, permanent magnets (if applicable), and the air gap. This core forms the magnetic circuit of a radial flux motor. In that circuit, flux travels perpendicular to the axis of rotation.   The radial layout shapes how electric motors produce torque. Each radial motor stator core holds the windings, and each radial motor rotor core carries the magnets or coils. The air gap separates these two parts. A small gap strengthens the magnetic coupling between them. Together, the five components turn electrical input into rotation in any motor of this type.   Key Takeaways A radial flux motor core has five main parts: stator, rotor, windings, magnets, and air gap. The stator stays still and holds the windings. The rotor spins and carries the magnets. Thin steel sheets stacked together reduce energy loss and keep the motor cool. A small, even air gap makes the motor stronger and more efficient. Good steel and careful assembly make the motor last longer and work better.   Stator: The Stationary Core of the Radial Flux Motor Core Yoke and Slot Structure The stator is a cylindrical iron core with slots cut into its inner surface. These slots hold the copper coils that carry current. The radial motor stator core sits around the rotor and guides flux across the gap between them.   The yoke forms the outer ring of this ferrous core. It connects the slot teeth and completes the magnetic circuit. A thick yoke carries more flux without saturating, while a thin yoke saves weight. Engineers balance these two needs during design. The yoke also anchors the stator inside the motor housing.   Laminated Steel Construction Builders stack thin steel sheets to form the stator and rotor. Each laminate carries an insulating coating that blocks eddy currents. Stacked cylindrical laminations reduce energy losses and keep the core cool. SHUNZHISHEN TECHNOLOGY supplies high-grade lamination steel for stator cores, and the same grade suits rotor stacks.   Heat removal deserves attention in radial designs. The stator core carries heat away from the coils, and steel conducts heat less readily than copper. EMWorks notes the tradeoff: In contrast, radial machines must dissipate heat through the stator core, typically composed of steel with lower thermal conductivity.   Designers therefore treat the stator as both a magnetic path and a thermal path. Slot liners and impregnation resin help move heat from the winding into the iron. Ferromagnetic cores with tight stacking tolerances transfer flux with fewer losses. Careful material choice keeps the motor efficient under continuous load.   Rotor: The Rotating Component Permanent Magnet and Wound Rotor Types The rotor sits inside the stator in a traditional radial flux motor. This inner placement lets the stator surround the rotating part and drive it through the magnetic field. The rotor turns on a shaft and carries the moving half of the magnetic circuit.   Most designs place permanent magnets on the rotor. These magnets supply a fixed magnetic field without any external current. A wound rotor takes a different path. It carries a coil that receives current through slip rings or an exciter. Each type suits different duties. Magnet rotors favor compact, efficient machines, while wound rotors allow field control from outside the machine. Both types rely on the same radial flux rotor geometry, where the field crosses the gap in a radial direction.   Rotor Lamination Stack Builders assemble the radial motor rotor core from stacked cylindrical laminations. Thin steel sheets press together into a solid stack, and each sheet carries an insulating layer. The stack holds the magnets or coils in place and gives the flux a low-loss path through the iron.   SHUNZHISHEN TECHNOLOGY offers rotor lamination steel options for these stacked cylindrical laminations. The right grade limits eddy current losses and keeps the rotor cool at speed. Magnets mounted on the surface need a secure retention sleeve or band. Interior magnets sit in pockets cut into the stack. Either layout keeps the magnets on the rotor firmly fixed against centrifugal force. A well-built stack also balances well, and balance matters at high speed. Precise stacking and tight tolerances protect the air gap and keep the motor quiet.   Core Design Elements: Windings, Magnets, and Air Gap Distributed Windings and Copper Coils Most radial flux motors use distributed windings in the stator slots. These windings spread across several slots per pole, and this spread smooths the magnetic field and cuts torque ripple. Copper coils carry the current that builds the field. The ferrous cores inside the coils concentrate that field and give it a defined path.   Permanent magnet placement offers a key design variation. Surface-mounted magnets sit on the rotor surface and deliver high flux with a simple build. Interior magnets sit in pockets inside the rotor, and this layout adds reluctance torque and protects the magnets at speed. Each choice shapes how the coils and magnets interact across the gap.   Flux Path Across the Air Gap Magnetic flux crosses the air gap in a radial direction, perpendicular to the axis of rotation. This radial path defines the machine type. The gap sets the magnetic flux density that reaches the rotor, and a small gap raises permeance and efficiency. Builders hold the air gap to tight tolerances, because a wide gap wastes flux and weakens torque.   The air gap also demands precise assembly. A small, even gap keeps magnetic flux density high and losses low. The radial motor stator core and radial motor rotor core must align well, or the flux path distorts. Careful machining of the iron and balanced rotor stacks protect this critical space. A well-controlled air gap lets the coils, magnets, and iron work as one efficient magnetic circuit.   The five components of a radial flux motor core work as one magnetic circuit. The stator and rotor cores carry the flux path, the windings generate the field, the magnets supply a fixed field, and the air gap links the two sides.   Material quality shapes performance. Lamination steel from suppliers like SHUNZHISHEN TECHNOLOGY directly affects efficiency and torque density, so the grade of the radial motor stator core and radial motor rotor core matters. Precise assembly completes the picture. Tight tolerances keep the gap even and let flux transfer with minimal loss, and that discipline separates a good motor from a great one.   FAQ What are the five main components of a radial flux motor core? The core contains a stator, a rotor, windings, permanent magnets, and an air gap. The stator and rotor carry the magnetic path. The windings and magnets create the field. The air gap links both sides and lets flux cross between them. Why do manufacturers stack thin steel laminations instead of one solid block? Thin sheets with insulating coatings block eddy currents. A solid block would let these currents circulate freely and waste energy as heat. Stacked laminations keep losses low and help the motor run cooler under load. How does the air gap affect motor performance? A small, even gap raises magnetic permeance and efficiency. A wide or uneven gap wastes flux and weakens torque. Builders hold tight tolerances on the radial motor stator core and radial motor rotor core to protect this space. Do all radial flux motors use permanent magnets? No. Many designs mount magnets on the rotor for a compact, efficient build. Others use a wound rotor that receives current through slip rings or an exciter. Each type suits different duties, and both share the same radial geometry. Why does lamination steel grade matter? The steel forms the magnetic path in the radial motor stator core and radial motor rotor core. A suitable grade limits eddy current losses and carries flux with fewer losses. Material quality directly shapes efficiency and torque density in electric motors.

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).