+86-574-87520996
sales@fzmag.com
Laminated magnets suppress eddy-current loss by structurally interrupting the current loops:
Root cause of eddy current: Sintered NdFeB is electrically conductive. In a time-varying magnetic field (high speed / high frequency), flux change induces large closed-loop eddy currents inside the solid magnet. The I²R loss is dissipated as heat, raising temperature and reducing efficiency.
Skin depth quantification: The penetration depth of an alternating field into a conductor is
δ = √(2ρ / ωμ)
For sintered NdFeB (ρ ≈ 1.4×10⁻⁶ Ω·m), skin depth is only ~0.6 mm at 1 kHz, ~0.27 mm at 5 kHz, and ~0.19 mm at 10 kHz — at high frequency, the flux change is concentrated in a very thin surface layer.
How lamination breaks the loop: Slice the magnet into 0.20–0.50 mm sheets (much thinner than the skin depth) and coat each with a 10–25 μm epoxy / ceramic / polyimide insulation layer. The eddy-current path is then confined within each individual sheet — it cannot cross the insulation to form a large loop. Eddy-current loss scales with the cube of lamination thickness: a 0.35 mm sheet vs a 5 mm solid block reduces single-sheet loss by ~99.7% (i.e. (0.35/5)³ ≈ 0.34%).
Engineering result: Total stack eddy-current loss is typically reduced 60–90% versus an equivalent solid magnet. Steady-state magnet temperature drops 30–50%, enabling higher speed, higher power density, and longer service life.
How Laminated NdFeB Magnet Technology Solves the Eddy-Current Problem and Unlocks the Next Generation of High-Frequency Electrical Machines
Laminated magnets — also called laminated NdFeB magnets, laminated permanent magnets, or stacked sintered magnet assemblies — are a specialized class of permanent-magnet components built from many thin sheets of sintered NdFeB (neodymium-iron-boron) bonded together with an inter-lamination insulation layer. They are the engineering answer to one of the most stubborn problems in modern electrical-machine design: how to operate a high-energy-density rare-earth magnet in a high-speed or high-frequency environment without losing a large fraction of that energy to internal eddy currents.
In a conventional solid sintered NdFeB magnet, the magnet itself is electrically conductive. When the rotor or stator is exposed to a rapidly changing magnetic field — for example, the slotting harmonics of a high-speed permanent-magnet motor, the variable reluctance field of a magnetic gear, or the high-frequency excitation of a magnetic-bearing spindle — circulating eddy currents are induced inside the magnet body. These currents do no useful work, generate heat, raise the magnet temperature, increase the risk of irreversible demagnetization, and ultimately cap the achievable speed, power density, and efficiency of the machine.
Laminated magnets solve this problem by slicing the magnet into thin sheets, typically 0.20 mm to 0.50 mm thick, and coating each sheet with a thin electrically insulating layer before stacking. The result behaves magnetically almost like a solid magnet of the same total height, but electrically it is broken up into many isolated layers in which eddy currents cannot easily form. The eddy-current loss can be reduced by 60 percent to more than 90 percent, magnet temperature rise can drop by 30 to 50 percent, and the machine can run faster, cooler, and more efficiently.
Laminated magnets are now standard in the most demanding high-performance machines on the market. They are inside the axial-flux traction motors of premium electric vehicles, the direct-drive generators of multi-megawatt wind turbines, the high-speed servo motors driving semiconductor pick-and-place heads, the linear motors moving photolithography stages, and the high-speed magnetic couplings that hermetically seal chemical pumps. This guide explains how laminated magnets work, where they are used, what design parameters matter, and how FAIZEAL engineers and manufactures laminated magnet assemblies to customer specification.
Every electrically conductive material exposed to a time-varying magnetic field develops eddy currents. In a permanent-magnet motor, the time-varying component of the magnetic field at the magnet surface comes from several sources: the slotting of the stator or rotor laminations, the inverter-induced current harmonics, the variable reluctance as the magnet moves past salient poles, and — most severely — the high fundamental electrical frequency at high mechanical speed.
The classic skin-depth formula gives the depth to which an alternating magnetic field penetrates a conductor:
skin depth δ = √(2ρ / (ω·μ)) where ρ is the electrical resistivity, ω is the angular frequency, and μ is the magnetic permeability.
For a sintered NdFeB magnet, the resistivity is roughly 1.4 × 10⁻⁶ Ω·m and the relative permeability is about 1.05. At 1 kHz electrical frequency, the skin depth is on the order of 0.6 mm. At 5 kHz it is around 0.27 mm, and at 10 kHz it drops to about 0.19 mm. This means that in any high-speed or high-frequency machine, the magnetic flux change is concentrated in a thin skin layer on the magnet surface — exactly the layer in which eddy currents will flow and where resistive heating is greatest.
A solid NdFeB magnet of 5 mm or 10 mm thickness cannot dissipate this skin-layer heat quickly. The center of the magnet stays cool but the surface can overheat, raising the local temperature above the magnet's maximum operating limit and causing partial demagnetization. The result is a derated machine: lower continuous power, lower peak torque, more cooling required, and a shorter magnet life.
Lamination breaks the magnet into many thin slices, each thinner than the skin depth at the operating frequency. Because each slice is so thin, the eddy currents that can form within it are small, and the ohmic loss is proportional to the cube of the lamination thickness. A 0.35 mm lamination, for example, generates roughly 1/100 of the eddy-current loss of a 5 mm solid block at the same frequency. The cumulative effect across the stack is dramatic: typical machines see 60 to 90 percent reduction in total magnet eddy-current loss when switching from a solid magnet to a properly laminated magnet of the same magnetic grade and overall volume.
A laminated magnet is a carefully engineered composite. The production chain has five critical steps: slicing, surface preparation, insulation coating, stacking and bonding, and final magnetization.
Sintered NdFeB blanks are first produced by the standard powder-metallurgy route: alloy melting, hydrogen decrepitation, jet milling, pressing in a magnetic field, sintering, and annealing. The resulting dense magnet has the magnetic properties the customer needs — for example, N42SH or N40UH — and is dimensionally accurate within roughly ±0.05 mm.
The blank is then sliced into thin sheets. The two common slicing methods are wire electrical discharge machining (wire EDM) and diamond sawing. Wire EDM is preferred for high-precision work and for complex shapes, because it can cut very thin slices with no mechanical stress on the brittle NdFeB material. Diamond sawing is faster and more economical for large volumes of simple shapes. Lamination thickness is typically held to ±0.02 mm.
Each slice is then surface-treated to apply an electrically insulating layer. The most common options are an epoxy resin coating of 10 to 25 μm, a ceramic coating of 5 to 10 μm for high-temperature applications, an organic polyimide coating of 15 to 30 μm for very high reliability, or a parylene coating of 5 to 15 μm for medical, semiconductor, and vacuum applications. The coating must be thin enough not to consume useful magnetic volume, but thick and uniform enough to break the electrical conduction path between adjacent sheets.
The coated sheets are stacked in a precision fixture that aligns them within 0.02 to 0.05 mm total indicated runout, and bonded with a structural adhesive — usually a high-temperature-curing two-component epoxy, an anaerobic adhesive, or in some cases a cyanoacrylate for low-temperature assemblies. The stack is then cured, sometimes under pressure and heat, to lock the laminations into a single rigid assembly.
Finally, the laminated stack is magnetized. Because the magnet is now an assembly, it can be magnetized in the same multi-pole magnetizer that would be used for a solid magnet of the same outer dimensions, or it can be magnetized piece-by-piece before stacking if a particular field geometry is required. Halbach arrays, skewed magnetization, and high-pole-count patterns (up to 48 poles) are all achievable.
The result is a magnet assembly that is magnetically equivalent to a solid sintered NdFeB magnet of the same overall dimensions and grade, but with dramatically lower eddy-current loss at high frequency.
The benefits of laminated magnets in high-performance electrical machines can be grouped into seven categories.
First, eddy-current loss reduction. As described above, lamination cuts magnet eddy-current loss by 60 to 90 percent depending on lamination thickness, operating frequency, and insulation quality. This is the primary engineering reason to choose a laminated magnet.
Second, lower temperature rise. Because the heat generated inside the magnet is much lower, the steady-state operating temperature of the magnet drops by 30 to 50 percent compared to a solid magnet under the same load. This directly improves reliability, allows higher continuous power output, and extends magnet life.
Third, higher efficiency. Magnet eddy-current loss is part of the total machine loss budget. Reducing it directly raises the electrical efficiency of the motor or generator, often by 1 to 3 percentage points — a very large number in machine design.
Fourth, higher achievable speed. Because the magnet no longer self-heats as severely, the machine can run at higher mechanical speed without thermal derating. Laminated magnets are routinely used in machines designed for 20,000 to 100,000 RPM and beyond.
Fifth, demagnetization safety. The lower operating temperature means the magnet stays further away from its maximum-use temperature and its intrinsic coercivity is preserved. This improves the safety margin against irreversible demagnetization during fault events such as short-circuit current or overload.
Sixth, better high-frequency response. For machines that operate at high electrical frequency — for example, very high-speed spindles, magnetic bearings, and high-pole-count machines — the lamination thickness can be chosen so that the magnet is essentially transparent to the high-frequency field. This enables topologies that would be impossible with solid magnets.
Seventh, compatibility with high-grade materials. The most powerful NdFeB grades (N52, N50M, N48SH, N45UH, N42EH) and samarium-cobalt grades (Sm₂Co₁₇, SmCo 2:17) are all available in laminated form. This means a designer does not have to choose between lamination and high performance — both can be achieved.
Laminated magnets are used wherever a high-energy-density permanent magnet must operate in a high-speed or high-frequency magnetic environment. The major application fields are described below, with the specific machine types and real-world examples in each.
Modern EV traction motors are the largest single market for laminated NdFeB magnets. The combination of high torque density, high speed (15,000 to 25,000 RPM is now common), high inverter switching frequency, and continuous duty cycle creates a perfect storm of eddy-current loss in a solid magnet. Premium EV makers use axial-flux and high-speed radial-flux motors that depend on laminated magnets for both performance and durability.
Specific machine platforms that use laminated magnets include axial-flux motors from manufacturers such as YASA, Magnax, Phi-Power, EMRAX, and various Tier-1 EV suppliers, high-speed radial-flux permanent-magnet motors that target 20,000+ RPM operation, and in-wheel motors that combine high power density with limited cooling. The performance benefits in this segment are direct: more torque per kilogram, more power per liter, longer range on the same battery, and better thermal management during sustained highway driving.
Multi-megawatt wind turbines — both onshore and offshore — increasingly use direct-drive permanent-magnet generators in which the rotor carries hundreds of kilograms of NdFeB magnets rotating at low mechanical speed but very high electrical frequency. The magnet poles on a 5 MW direct-drive generator are often larger than 100 mm in length, and the electrical frequency can exceed 100 Hz at rated speed. Lamination of these large magnets is now a standard engineering practice for turbine manufacturers such as Vestas, Siemens Gamesa, Goldwind, Mingyang, and Envision.
Industrial servo motors for robotics, CNC machine tools, semiconductor pick-and-place machines, and high-speed spindles operate at base speeds of 3,000 to 12,000 RPM and field-weakened speeds well above 20,000 RPM. Major servo-motor makers — including FANUC, Yaskawa, Mitsubishi, ABB, Siemens, Beckhoff, and Kollmorgen — use laminated magnets in their premium product lines to push continuous torque density higher and to reduce the thermal load on the machine frame.
Linear motors for semiconductor lithography, wafer inspection, flat-panel-display production, precision CNC, and magnetic-levitation transport all use high-grade NdFeB magnets in a periodic Halbach or alternating-pole pattern moving at high speed relative to the coil array. The relative velocity between magnet track and coil generates the same kind of high-frequency magnetic field at the magnet surface that creates eddy-current loss in a rotating machine. Laminated magnet tracks — built as long stacked assemblies of thin NdFeB sheets in a precision-ground aluminum or steel track — are standard in these applications. The semiconductor industry, in particular, requires very thin laminations (0.20 mm or less) to enable the very high acceleration and velocity of wafer-stage and reticle-stage motion.
Magnetic couplings transfer torque through a non-magnetic containment shell using only magnetic forces. They are widely used in hermetic pumps for chemical, pharmaceutical, and food-processing applications. As the coupling speed rises, the relative velocity between the inner and outer magnet rings increases, and the alternating magnetic field in the containment shell drives eddy currents both in the shell and in the magnet itself. High-speed magnetic couplings — for example, those operating at 5,000 to 20,000 RPM — are routinely built with laminated NdFeB magnets to control magnet heating and to allow the coupling to transmit rated torque continuously rather than only in short bursts.
Active and passive magnetic bearings, as well as high-speed flywheels for energy storage and pulse-power applications, use permanent-magnet-biased bearing paths that operate at very high mechanical speed. Laminated magnets in the bias path reduce rotor losses and enable stable levitation at speeds up to and beyond 100,000 RPM.
Aircraft actuators, UAV propulsion motors, and space-grade mechanisms all require high torque density in a small envelope, often at high speed and with very tight thermal management. Laminated SmCo and laminated high-grade NdFeB magnets are used in these applications because they combine the high magnetic performance of rare-earth materials with the high-speed capability of lamination. SmCo is preferred where the operating temperature exceeds 200°C or where radiation tolerance is required.
Magnetic gears use the interaction of high-pole-count magnet arrays to transmit torque without contact. The internal magnet fields in a magnetic gear are very high frequency, and the magnets themselves are exposed to rapidly varying fields. Laminated magnets in magnetic gears reduce loss and enable higher power density than is achievable with solid magnets.
Small to medium permanent-magnet generators for aerospace, military, marine, and remote-power applications often run at high speed to extract maximum power from a small envelope. Laminated magnets are used in these machines to enable the high electrical frequency and continuous-duty operation required.
High-end research and medical instruments, including magnetic refrigeration prototypes and certain types of particle accelerators and mass spectrometers, use laminated magnets to push operating frequency higher while keeping the magnet cool.
The choice of magnetic material is one of the first design decisions for a laminated magnet. The most common options are sintered NdFeB, samarium-cobalt (SmCo), and bonded NdFeB, with aluminum-nickel-cobalt (AlNiCo) reserved for very specific high-temperature or temperature-stable applications.
Sintered NdFeB is the workhorse of laminated-magnet design. It offers the highest energy product of any commercial permanent-magnet material, with grades from N35 to N52 in the standard temperature range and from N33M to N50M, N30SH to N48SH, N28UH to N42UH, N28EH to N40EH, and N28AH to N38AH in the high-temperature and ultra-high-temperature grades. The maximum operating temperature depends on grade: N35 to N42 are limited to about 80°C continuous, N42M to N50M reach about 100°C, N30SH to N48SH reach about 150°C, N28UH to N42UH reach about 180°C, N28EH to N40EH reach about 200°C, and N28AH to N38AH reach about 220°C or higher with proper design. Sintered NdFeB is the natural choice for almost all EV, wind, servo, and linear-motor applications.
Samarium-cobalt (SmCo) is the material of choice when the operating temperature exceeds about 200°C, when radiation tolerance is required, or when long-term thermal stability is critical. SmCo 1:5 (SmCo₅) operates from about 250°C to 300°C continuous. SmCo 2:17 (Sm₂Co₁₇) operates from about 300°C to 350°C continuous. SmCo is more expensive than NdFeB and has a lower energy product, but in many high-temperature and aerospace applications there is simply no substitute. Laminated SmCo magnets are routinely produced for downhole oil and gas tools, aerospace actuators, and high-temperature generators.
Bonded NdFeB is made by compression-molding or injection-molding a mixture of NdFeB powder and a polymer binder. Bonded NdFeB can be produced in very complex shapes with tight tolerances, but its magnetic properties are lower than sintered NdFeB, and it is rarely used in laminated form because the polymer binder itself acts as an insulator. Where complex geometry is more important than magnetic performance, bonded NdFeB may be the right answer; in most high-performance laminated applications, sintered NdFeB or SmCo is preferred.
AlNiCo has excellent temperature stability but a much lower coercivity than NdFeB or SmCo, and it is rarely used in laminated form. It appears mainly in legacy applications and in certain instruments where a specific temperature coefficient of magnetization is required.
The manufacturing process for laminated magnets has six critical parameters that determine the final quality.
Lamination thickness is the single most important parameter. Typical choices are 0.20 mm for high-frequency applications above 1 kHz, 0.35 mm for the most common high-speed motor applications, 0.50 mm for moderate-speed applications, and 1.00 to 2.00 mm for very low-frequency or low-cost applications. Each lamination is held to a thickness tolerance of about ±0.02 mm.
Lamination thickness tolerance control is critical because any variation in thickness between sheets accumulates in the final stack height. A 0.02 mm variation across a 30-sheet stack would be 0.6 mm of total height error if not controlled, so modern lamination lines use precision slicing and precision stacking fixtures to keep total stack height within ±0.05 mm even on stacks of 50 to 100 sheets.
Insulation layer uniformity is the second key parameter. A thin, uniform insulation layer that reliably covers every sheet — including the edges — is essential. A single pinhole or uncoated edge can create an electrical short between two adjacent sheets, which in turn creates a localized eddy-current path that can run hot and degrade the magnet. Modern production lines use dip-coating, spray-coating, or electrophoretic deposition (E-coat) to ensure complete coverage, and 100% inspection of insulation resistance between adjacent sheets is part of the standard QA flow.
Bonding strength between laminations is the third key parameter. The structural adhesive used to bond the stack must be strong enough to withstand centrifugal force at the operating speed of the machine, thermal cycling over the operating temperature range, and any vibration or shock loads imposed by the application. Two-component high-temperature-curing epoxy is the most common choice. For SmCo magnets that will see temperatures above 200°C, ceramic-based adhesives or even diffusion bonding may be required.
Stack alignment precision is the fourth key parameter. The individual laminations must be aligned in a precision fixture so that the total indicated runout (TIR) of the stack is within about 0.02 to 0.05 mm. Misalignment creates magnetic asymmetry that produces vibration, noise, and uneven torque in the finished machine.
Dimensional accuracy of the finished stack is the fifth key parameter. After bonding, the stack is ground to its final dimensions — outer diameter, inner diameter, height, flatness, and parallelism. Tight-tolerance grinding to ±0.02 mm is standard.
Magnetization pattern is the sixth key parameter. The finished stack is magnetized in a multi-pole magnetizer. The number of poles, the magnetization direction (radial, axial, Halbach, skewed), and the field strength must all match the application. For a Halbach array, the laminations are sometimes magnetized individually before stacking, so that each sheet carries the correct angular magnetization direction for its position in the array.
FAIZEAL customizes laminated magnets along eight major parameter axes.
The first axis is lamination thickness. Standard thicknesses are 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.50 mm, 0.70 mm, 1.00 mm, and 1.50 mm. Custom thicknesses between 0.10 mm and 2.00 mm can be produced for special applications.
The second axis is insulation material and thickness. Epoxy resin at 10 to 25 μm is the most common choice. Ceramic (Al₂O₃) at 5 to 10 μm is preferred for high-temperature applications. Polyimide at 15 to 30 μm is preferred for high-reliability applications. Parylene at 5 to 15 μm is preferred for medical, vacuum, and semiconductor applications.
The third axis is stack height and lamination count. Stacks from 5 mm to 200 mm in total height, with lamination counts from 10 to 500, are all routine.
The fourth axis is stack geometry. Arc segments, rectangular blocks, D-shapes, T-shapes, custom profiles, Halbach array configurations, and skew-magnetized configurations are all available.
The fifth axis is material grade. N35 through N52, M, H, SH, UH, EH, and AH grades of NdFeB, and SmCo 1:5 and 2:17 grades, are all available. Each grade is selected based on the operating temperature, the required energy product, and the cost target of the application.
The sixth axis is surface treatment. Ni-Cu-Ni triple plating at 20 to 35 μm is the standard. Zn plating at 5 to 15 μm is the cost-effective option. Black epoxy is preferred where additional insulation is required. Everlube, parylene, and other specialty coatings are available for specific environments.
The seventh axis is dimensional tolerance. Standard tolerance is ±0.05 mm on length, width, and height. Precision tolerance of ±0.02 mm is available on request. Flatness and parallelism are typically held to 0.02 to 0.05 mm.
The eighth axis is magnetization pattern. Standard multi-pole magnetization from 4 to 48 poles is routine. Halbach arrays with up to 8 segments per pole period can be supplied. Skewed magnetization, surface magnetization, and custom field profiles are all available.
The typical lamination thickness for an EV traction motor operating at 15,000 to 25,000 RPM with an electrical fundamental frequency of 500 Hz to 1 kHz is 0.30 to 0.50 mm. The most common grade is N42SH or N40UH, which gives the right balance of high energy product and high coercivity for sustained high-temperature operation. The most common insulation is epoxy at 15 to 20 μm. The most common stack geometry is an arc segment (rotor segment for a radial-flux motor) or a fan-shaped trapezoidal segment (rotor segment for an axial-flux motor).
Wind generator magnets are typically much larger — arc segments up to 200 mm or more in length. The electrical frequency is low (10 to 100 Hz) because the mechanical speed is low, so the lamination thickness can be relaxed to 0.50 mm or even 1.00 mm. The material grade is usually N38SH or N40SH because the operating temperature is moderate and the magnet cost is a significant fraction of the generator cost.
Servo motor magnets are typically small arc segments or rectangular blocks. The electrical frequency can exceed 2 kHz at field-weakened speeds, so the lamination thickness is usually 0.20 to 0.35 mm. The most common grade is N40SH or N42SH. The tightest possible dimensional tolerance is required because servo motor torque ripple is highly sensitive to magnet geometry.
Linear motor magnets are typically rectangular blocks or Halbach-array segments. Lamination thickness is usually 0.20 to 0.50 mm depending on the speed and acceleration. Halbach arrays are very common because they concentrate the magnetic field on the coil side and reduce stray field on the back-iron side, which simplifies the mechanical design of the linear track.
Magnetic coupling magnets are typically full rings or arc segments, often in a Halbach configuration to maximize torque transmission. Lamination thickness depends on the operating speed — at 3,000 RPM a 0.50 mm lamination is fine; at 15,000 RPM a 0.20 mm lamination is preferred. Material grade is usually N40SH or N42SH.
Magnetic bearing magnets are usually rings or arc segments with very tight dimensional tolerance and very uniform magnetization, because any magnetic asymmetry creates a force ripple that excites the bearing. Lamination thickness is usually 0.20 to 0.35 mm. The material grade is usually N42SH or N40UH depending on the operating temperature.
Every laminated magnet that leaves the FAIZEAL factory goes through a documented quality-control flow.
Incoming NdFeB blanks are dimensionally inspected, magnetic-property tested on a vibrating-sample magnetometer (VSM) or Helmholtz coil, and visually inspected for cracks or inclusions.
Laminations are dimensionally inspected on each sheet — thickness at multiple points, length, width — to a tolerance of about ±0.02 mm. Sheets outside tolerance are rejected.
Insulation coating is visually inspected and tested for insulation resistance between adjacent sheets. A typical acceptance criterion is greater than 10 MΩ at 100 V between any two adjacent sheets.
Stacked assemblies are dimensionally inspected — total height, outer diameter, inner diameter, flatness, parallelism, total indicated runout. A typical acceptance criterion on stack height is ±0.05 mm.
Bonded assemblies are pull-tested to verify adhesive strength. A typical acceptance criterion is greater than 20 MPa shear strength between adjacent sheets, or as required by the customer specification.
Magnetized assemblies are field-mapped on a Helmholtz coil or gauss-meter fixture to verify that the magnetic field distribution matches the design. The peak surface field, the harmonic content, and the field uniformity are all logged.
Finished assemblies are 100% visually inspected for cracks, chips, and surface defects. Selected samples from each production batch are sent for thermal cycling, vibration testing, and high-temperature aging as required by the customer specification.
FAIZEAL is ISO 9001:2015 certified. Material certificates, dimensional inspection reports, magnetic property reports, and traceability records are provided with every shipment.
The decision between a laminated magnet and a solid sintered magnet is fundamentally a decision about how much eddy-current loss the application can tolerate.
A solid sintered NdFeB magnet is the right choice when the operating speed is low, the electrical frequency is low, the operating temperature is moderate, and the cost target is tight. Typical applications include low-power consumer motors, simple DC brushless motors, magnetic sensors, and magnetic fixtures. A solid magnet is cheaper to produce and offers slightly higher magnetic performance per unit volume because the insulation layer does not consume any of the active magnetic material.
A laminated NdFeB magnet is the right choice when the operating speed is high, the electrical frequency is high, the operating temperature is high, or the efficiency target is aggressive. Typical applications include EV traction motors, wind generators, high-speed servo motors, linear motors, high-speed magnetic couplings, magnetic bearings, and aerospace motors. A laminated magnet is more expensive to produce and consumes a small percentage of its active volume in insulation, but the reduction in eddy-current loss, the lower temperature rise, the higher achievable efficiency, and the higher continuous power output more than justify the additional cost.
A useful rule of thumb is that any magnet exposed to an electrical fundamental frequency above about 500 Hz, or any magnet that operates at a surface speed above about 50 m/s, will benefit from lamination. Below those thresholds, lamination is a marginal improvement and may not be cost-justified.
The laminated magnet market is being driven by four major forces.
First, the rapid growth of the electric vehicle market. Every premium EV traction motor today uses laminated magnets. As the EV market grows toward 40 to 50 million vehicles per year by 2030, the demand for laminated NdFeB will scale with it.
Second, the rapid growth of direct-drive wind turbines. Offshore wind in particular is moving to larger and larger direct-drive generators, all of which use laminated magnets in their rotor.
Third, the rapid growth of high-speed industrial automation. Semiconductor manufacturing, lithium battery production, and high-end CNC all require high-speed servo and linear motors, all of which use laminated magnets.
Fourth, the electrification of aerospace. Electric vertical-takeoff-and-landing (eVTOL) aircraft, hybrid-electric regional aircraft, and full-electric urban air mobility vehicles all use high-speed high-power-density motors, all of which benefit from laminated magnets.
The market for laminated NdFeB magnets is expected to grow at a compound annual rate of more than 15 percent over the next decade, significantly faster than the underlying NdFeB market. The supply chain for laminated magnets is more specialized than the supply chain for solid NdFeB magnets, and FAIZEAL's integrated capability — from raw alloy production through final magnetization — is well positioned to serve this growth.What is the minimum lamination thickness FAIZEAL can produce? FAIZEAL can produce laminations as thin as 0.10 mm in research quantities and 0.20 mm in production quantities. For most high-frequency applications, 0.20 to 0.35 mm provides the best balance of performance, manufacturability, and cost.
Can FAIZEAL produce Halbach-array laminated magnets? Yes. Halbach-array laminated magnets are one of our specialties. We can supply both radially-magnetized and axially-magnetized Halbach arrays, with the number of segments per pole period chosen to match the application. Common configurations are 3, 4, and 6 segments per pole period.
What lamination thickness should I use for a high-speed servo motor? For a servo motor operating at 6,000 to 12,000 RPM base speed and 20,000+ RPM field-weakened speed, a lamination thickness of 0.20 to 0.35 mm is typically the right choice. The exact thickness depends on the electrical frequency at the highest operating speed and on the customer's eddy-current loss budget.
How does lamination affect motor efficiency? Lamination reduces the magnet eddy-current loss, which is a direct component of the total machine loss. The efficiency improvement depends on the machine design but is typically in the range of 1 to 3 percentage points. For a machine that was 92% efficient as a solid magnet, the laminated version may reach 93% to 95% efficient.
What insulation type is best for high-temperature applications? For continuous operating temperatures above 180°C, a ceramic (Al₂O₃) insulation or a high-temperature polyimide insulation is preferred. For temperatures above 250°C, the magnet material should be SmCo and the insulation should be ceramic or no insulation (with a small air gap between sheets).
Can laminated magnets be used in high-torque applications? Yes. The lamination process does not significantly reduce the peak magnetic performance of the magnet. A laminated N42SH magnet has essentially the same peak field at the magnet surface as a solid N42SH magnet of the same dimensions. The laminated version simply runs cooler under continuous high-torque operation.
What is the difference between a laminated magnet and a segmented magnet? A segmented magnet is made by gluing together several pre-magnetized arc segments to form a ring or a sector. A laminated magnet is made by stacking many thin un-magnetized sheets, then magnetizing the finished stack. Segmented magnets reduce magnet material waste but do not significantly reduce eddy-current loss because each segment is still a solid block. Laminated magnets are the correct solution for eddy-current loss reduction.
How does FAIZEAL control stack height tolerance? Each lamination is sliced to ±0.02 mm thickness tolerance. The stacking fixture measures total stack height during assembly and adjusts the lamination count if necessary to reach the target height within ±0.05 mm total. A final grinding step on the bonded stack refines the height to the final specification.
What is the typical lead time for a laminated magnet prototype? For standard geometries, prototype lead time is 2 to 4 weeks. For custom geometries, lead time is 4 to 6 weeks including tooling. Production lead time after prototype approval is typically 4 to 8 weeks depending on volume.
Does FAIZEAL provide magnetization service? Yes. FAIZEAL has in-house multi-pole magnetizers capable of magnetizing assembled stacks of up to 500 mm in diameter with up to 48 poles. Halbach arrays, skewed magnetization, and custom field profiles are all available. We can also ship un-magnetized laminations for the customer to magnetize in their own fixture if that is preferred.
Laminated magnets are the enabling technology behind the highest-performance electrical machines in service today. They solve the eddy-current problem that limits solid sintered magnets at high speed and high frequency, and they do so without sacrificing the magnetic performance of the underlying NdFeB or SmCo material. From the axial-flux motors in premium electric vehicles to the direct-drive generators in multi-megawatt wind turbines, from the high-speed servo motors in semiconductor pick-and-place machines to the linear motors in photolithography stages, laminated magnets are quietly doing the work that makes the modern high-performance electrical machine possible.
FAIZEAL engineers, manufactures, and supplies laminated magnet assemblies in sintered NdFeB and SmCo, in geometries from 5 mm arc segments to 500 mm OD rings, in lamination thicknesses from 0.10 mm to 2.00 mm, and in stack heights from 5 mm to 200 mm. If you are designing a high-speed motor, a high-frequency generator, or a high-power-density magnetic system and you need a partner who can move from concept to production without losing the engineering details along the way, FAIZEAL is ready to help.
For a technical consultation, a custom quotation, or a sample request, contact FAIZEAL at sales@fzmag.com or visit www.fzmag.com.
