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Axial flux motors (AFMs) have surged from research labs into real products—from robotics and e-mobility to aerospace and distributed generation. Their disc-like geometry packs high torque in a short axial length, enabling thin, pancake-style machines that fit where traditional cylindrical (“radial flux”) motors struggle. What is an Axial Flux Motor? In an axial flux machine, magnetic flux travels parallel to the shaft (axially) across a flat air gap between a rotor disc with permanent magnets (or a wound field) and a flat stator disc with windings. By contrast, radial flux machines guide flux radially, across a cylindrical air gap between an inner rotor and outer stator. The axial configuration creates a large effective lever arm (mean radius), so for a given air-gap shear stress the torque scales roughly with the cube of radius and only linearly with axial length. That’s why AFMs tend to offer excellent torque density for a given mass and especially for limited axial space. Common AFM topologies Single-stator, single-rotor (SS-SR): Simplest build; unbalanced axial magnetic forces must be handled structurally. Double-rotor, single-stator (DR-SS): Rotors on both sides of one stator balance axial forces and double the active area for the same diameter. Double-stator, single-rotor (DS-SR): A central rotor sandwiched by two stators; also balances axial forces and doubles active copper. Yokeless and segmented armature (YASA-type): Segmented tooth modules without a continuous back iron reduce iron mass and eddy losses, thereby improving torque density. Coreless (air-core) stator: Eliminates iron teeth to remove cogging and iron losses virtually; great for smoothness and partial-load efficiency, but lower flux density and higher copper mass. PCB stator (very low power): Spiral copper traces on FR-4 or polyimide; exceptional thinness and precision for fans/micro-drives at low torque. Why Choose (or Not Choose) an AFM? Strengths High torque density at modest diameter; thin “pancake” packaging with short axial length. Low cogging potential (especially with coreless or yokeless designs), yielding smooth motion and low acoustic noise. Scalability in disc area: Large-diameter, low-speed direct-drive generators/motors (e.g., wind, flywheels, test benches). Short end-turns with concentrated windings (in many AFMs) reduce copper loss. Limitations Tighter air-gap control required: the flat faces must remain parallel under load and temperature. Thermal paths can be tricky: Large, thin discs need thoughtful heat extraction to avoid hot spots. Higher pole counts lead to higher electrical frequency at a given rpm (impacts inverter and losses). Manufacturing complexity for segmented stators, magnet fixtures, and rotor banding—especially at high rpm. Typical Performance Ranges (Indicative) Real performance depends on materials, cooling, control, duty cycle, and safety margins. The following ranges are conservative but useful for initial screening: Peak air-gap flux density (NdFeB): 0.6–0.9 T (teethed), 0.3–0.5 T (coreless) Specific electric loading (A, RMS): 20–60 kA/m (air-cooled), up to ~80 kA/m (aggressive liquid cooling) Continuous torque density: ~8–25 N·m/kg (well-cooled designs); peak can exceed 30–60 N·m/kg for short bursts Continuous power density: ~1–3 kW/kg; peak ~2–6 kW/kg (brief) Peak efficiency: 92–97% (properly optimized) Air gap: 0.3–1.5 mm typical (smaller at lower diameter/lower runout) Pole pairs: 6–40 (higher for large diameters/low speed) These are not hard limits; specialized designs, advanced cooling (spray/oil jet, cold plates), and premium magnets can exceed them. Losses and Efficiency Copper (I²R) losses: Dominant at high torque. Reduce via larger conductor cross-section, lower winding temperature, and higher fill factor (35–55% is typical with round or rectangular wire). Iron losses (hysteresis + eddy): Significant in teethed stators; reduce via thin laminations (0.1–0.35 mm), low-loss grades, or Soft Magnetic Composites (SMC) in 3D flux regions. Proximity & skin effect: Grow with electrical frequency and conductor geometry; mitigated by litz wire (low-power) or shaped bar conductors (higher power). Mechanical & windage: Rotating discs can incur windage; shrouding and smooth surfaces help. Inverter (switching + conduction) losses: Rise with electrical frequency (which rises with pole count at a given rpm). Correct device choice (SiC/MOSFET/IGBT), optimal PWM, and appropriate switching frequency are key. Thermal Management AFMs are thin and wide, so heat must be moved radially and axially out of copper and iron: Conduction paths: From teeth/tooth-coils to back-iron to housing; or directly from slot/coil to a liquid-cooled plate. Cooling options: Air convection over stator faces, with finned housings Liquid cold plates behind the stator Spray/oil-jet cooling directly on windings (advanced) Heat flux ballparks: ~5–15 kW/m² (forced air), ~30–100 kW/m² (liquid plates), and higher for direct oil impingement with careful insulation. Materials and Manufacturing Magnets NdFeB (N42–N52, H/EH grades): Highest energy density; watch max temperature (80–180 °C depending on grade). SmCo: Lower remanence but far better thermal stability (200–300 °C); excellent for high-temp or demag-robust designs. Ferrite: Cheap and stable but low energy density; viable with flux concentration structures. Stator iron Electrical steel laminations (0.1–0.35 mm) for teethed stators; SMC for complex 3D flux; or none for coreless. Windings Round-wire coils, rectangular “hairpin-style” (less common in AFM but possible), or litz for high frequency/small machines. PCB windings for micro-AFMs at low torque. Rotor integrity Magnets bonded to a steel or composite carrier; at higher rpm use non-magnetic banding (e.g., carbon fiber sleeves) to contain hoop stress and prevent magnet throw. Tolerances Flatness and parallelism matter. Air-gap uniformity within tens of microns improves efficiency and lowers acoustic noise. Dynamic balance typically to ISO 21940 G2.5 (or better) for quiet operation. AFM vs Radial Flux vs Transverse Flux Below is a practical comparison. Values are indicative—not absolutes—and assume competent cooling and modern materials. Attribute Axial Flux (AFM) Radial Flux (RFM) Transverse Flux (TFM) Packaging Thin “pancake”, short axial length Longer axial length, smaller diameter Bulky, complex magnetic paths Continuous torque density High (8–25 N·m/kg, higher with liquid cooling) Moderate–High (6–20 N·m/kg) Potentially very high but hard to realize Power density 1–3 kW/kg (cont.), 2–6 kW/kg (peak) 1–2.5 kW/kg (cont.), up to ~4 kW/kg (peak) High potential; complex manufacturing Pole count (typ.) Medium–High (6–40 pairs) Low–Medium (3–12 pairs) High Electrical frequency at given rpm Higher (due to more poles) Lower Higher Cogging & ripple Very low with coreless/yokeless Low–moderate (mitigation required) Depends on design; often challenging Cooling Needs careful planar

The electrification of transportation, robotics, and industrial systems has accelerated the development of compact, high-efficiency electric motors. Among the most innovative designs is the axial flux motor (AFM), known for its flat geometry, high torque density, and space-saving benefits compared to traditional radial flux machines. As industries search for ways to maximize efficiency, two integration pathways have gained prominence: combining axial flux motors with gearboxes for torque multiplication, and deploying them in direct-drive systems where mechanical transmission is eliminated. Understanding Axial Flux Motors Geometry and Operation Unlike radial flux motors, where the magnetic flux flows radially through the stator and rotor, axial flux motors have magnetic flux traveling parallel to the shaft. This flat, pancake-like design yields: High torque density – more torque per unit volume. Compact axial length – ideal for space-constrained applications. Short end windings – improved copper utilization and reduced resistive losses. Key Applications Axial flux motors are increasingly applied in: Electric vehicles (EVs and e-bikes). Aerospace propulsion systems. Industrial robotics. Renewable energy generators (e.g., wind turbines). Integration Pathways: Gearbox vs. Direct-Drive Two main methods exist for integrating axial flux motors into mechanical systems: With Gearboxes – AFMs provide speed, while the gearbox multiplies torque and adapts output to the load. Direct-Drive Systems – AFMs directly couple to the load, eliminating intermediate gears. Every method offers unique benefits and corresponding compromises. Axial Flux Motors with Gearboxes Why Pair with Gearboxes? Despite high torque density, axial flux motors often operate at higher speeds for efficiency. Gearboxes allow engineers to tailor torque and speed to the application. Common gearbox pairings include: Planetary gearboxes – compact, high load capacity. Harmonic drives – precision robotics. Cycloidal gearboxes – high-shock load resistance. Benefits of AFM-Gearbox Integration Torque Amplification – Enables smaller AFMs to drive heavy loads. Flexibility – Gear ratios provide versatility across varying duty cycles. Compact Powertrains – Flat AFMs plus planetary gearboxes reduce system footprint. Challenges Added complexity – More moving parts increase potential failure points. Efficiency losses – Gear meshing introduces friction and heat. Maintenance requirements – Lubrication, wear monitoring, and servicing. Case Example: Electric Vehicles In high-performance EVs, AFMs paired with single- or two-stage gearboxes provide the balance between compact design and road torque demands. Unlike radial flux motors, AFMs reduce overall drivetrain length, freeing space for batteries or passenger comfort. Axial Flux Direct-Drive Systems What Is Direct-Drive? Direct-drive integration eliminates the gearbox. The motor shaft connects directly to the load, relying on the AFM’s intrinsic torque density to deliver required performance. Benefits High Efficiency – No mechanical transmission losses. Reliability – Fewer moving parts reduce wear and failure points. Precision Control – Ideal for robotics and CNC systems requiring smooth motion. Compact Assembly – Reduces overall drivetrain size and weight. Limitations Size and Weight – To produce enough torque without gearing, larger AFMs may be needed. Cost – High-performance AFMs with strong permanent magnets can be expensive. Thermal Management – Direct-drive AFMs generate significant heat under high torque. Case Example: Wind Turbines Direct-drive axial flux generators boost efficiency, cut maintenance, and enhance reliability by eliminating gearboxes. Engineering Considerations in Integration Torque-Speed Matching With Gearboxes: Designers can select smaller AFMs running at high speed, with gear reduction providing torque. Direct-Drive: The AFM must be dimensioned to produce full required torque at low speed. Cooling and Thermal Management AFMs typically use liquid cooling or forced air systems due to their high torque density. In direct-drive systems, cooling becomes more critical because no gearbox dissipates part of the heat. Efficiency Trade-Offs AFM + Gearbox: Motor efficiency (≈95%) × gearbox efficiency (≈90–95%) = combined efficiency ~85–90%. Direct-Drive AFM: Efficiency closer to 93–96%, but requires larger motor footprint. Material Selection Magnets: High-grade NdFeB permanent magnets increase torque density. Laminations: Thin, high-permeability electrical steel reduces eddy current losses. Housing: Lightweight alloys or composites improve system compactness. Cost Factors Direct-drive: Higher initial motor cost, lower lifetime maintenance. Gearbox integration: Lower motor cost, but higher lifecycle maintenance costs. Comparative Analysis Factor AFM + Gearbox Direct-Drive AFM Efficiency 85–90% (due to gear losses) 93–96% (no gear losses) Torque Density High (gears amplify torque) Very high (large AFM required) Size/Weight More compact overall Larger motor, no gearbox bulk Cost Lower upfront, higher maintenance Higher upfront, lower maintenance Reliability Moderate (gear wear, lubrication) High (fewer moving parts) Applications EVs, robotics, industrial machinery Wind turbines, aerospace, precision drives Applications Across Industries Electric Mobility AFM + Gearbox: Suited for passenger EVs, motorcycles, and scooters needing dynamic torque curves. Direct-Drive AFM: Popular in e-bikes and in-wheel EV motors for compact integration. Aerospace Lightweight direct-drive AFMs in propulsion fans or actuator systems, where reliability outweighs cost. Robotics Harmonic-drive gearboxes plus AFMs enable precise manipulation with compact actuators. Renewable Energy Direct-drive axial flux generators in wind turbines reduce maintenance needs compared to gear-driven systems. Future Trends in Integration Advanced Cooling Techniques – Immersion cooling and micro-channel liquid cooling for high-torque AFMs. Additive Manufacturing – Custom laminated stacks and rotor designs to optimize direct-drive torque. Smart Gearboxes – Integration with sensors for predictive maintenance in AFM-driven systems. Rare-Earth-Free Designs –Using ferrite or composites to lessen dependence on critical materials. Hybrid Integration – Semi-direct systems with ultra-low-ratio gearboxes (≤2:1) to balance torque and efficiency. Axial flux motors represent a transformative leap in electric motor technology, offering high torque density and compact form factors that complement both gearbox integration and direct-drive systems. The choice between these pathways depends on the specific application: gearboxes provide flexibility and torque multiplication for mobility and robotics, while direct-drive systems maximize efficiency and reliability in renewable energy and aerospace. As manufacturing techniques, magnet materials, and thermal management technologies advance, the line between gearbox-assisted and direct-drive axial flux applications will blur, enabling even more efficient, compact, and durable electromechanical systems for the industries of tomorrow.

Washing machines are vital household appliances, offering convenience, efficiency, and reliable cleaning performance worldwide. While most people are familiar with the drum, detergent drawer, and water inlet, the drain motor is one of the most important yet often overlooked components. Without it, dirty water would remain trapped in the tub, preventing the wash cycle from completing properly. This guide explores how a drain motor works in washing machines, its components, working principles, maintenance tips, and troubleshooting techniques. Whether you are an appliance repair technician, an engineering student, or a curious homeowner, this article will give you a complete understanding of the drain motor’s role. What is a Drain Motor in a Washing Machine? The drain motor, also called the drain pump, expels dirty water from the washer after washing and rinsing cycles. It works in combination with the drain pump assembly, hoses, and control circuitry to ensure water flows out to the household drain system. Key Functions: Removes dirty water after the wash cycle. Expels rinse water after the rinse phase. Prepares the tub for spinning by eliminating excess water. Prevents water stagnation that could cause odors or mold. Types of Drain Motors While the core function remains the same, drain motors vary depending on washing machine design and manufacturer. Drain Motor Type Description Common Usage Synchronous AC Motor Uses alternating current to drive the pump impeller at a fixed speed. Common in front-load machines. Universal Motor Operates on AC or DC, higher speed capability. Found in some high-speed draining models. DC Brushless Motor Uses electronic commutation for quiet and efficient operation. Used in premium energy-efficient machines. Main Components of a Drain Motor System Understanding the parts of a drain motor assembly is key to understanding its operation. Motor Housing Shields internal parts from water, dust, and physical damage to ensure reliable operation. Rotor and Stator Rotor: The rotating component that drives the impeller. Stator: The stationary coil assembly that creates the magnetic field. Impeller A small fan-like structure connected to the rotor that pushes water through the drain hose. Shaft Seal Prevents water from leaking into the motor chamber. Electrical Connector Links the motor to the washing machine control board or timer. Drain Pump Housing Houses the impeller and channels water flow from the tub directly into the drain hose. How a Drain Motor Works – Step-by-Step Process Let’s explore the step-by-step operation of a washing machine drain motor during its cycle. Step 1: Control Signal Activation At the end of a wash or rinse cycle, the washing machine control board sends an electrical signal to the drain motor. Step 2: Motor Rotation The motor starts spinning the impeller, which generates a centrifugal force that moves water from the tub into the pump chamber. Step 3: Water Movement The spinning impeller pushes water into the drain hose, which is connected to the household drain pipe. Step 4: Tub Emptying The motor continues running until water level sensors or timers indicate the tub is empty. Step 5: Automatic Shut-off Once draining is complete, the motor stops to conserve energy and prepare for the next cycle. The Science Behind the Drain Motor Electromagnetic Operation Most drain motors generate a rotating magnetic field via stator coils, which then drives the rotor to pump water. Hydrodynamic Pumping The impeller uses hydrodynamic principles to convert rotational energy into kinetic energy, pushing water out through the pump housing. Synchronous vs. Asynchronous Operation Synchronous motors maintain a fixed speed matching the power supply frequency. Asynchronous motors can have slight speed variations depending on load. Drain Motor in Different Washing Machine Types Front-Load Washing Machines Use high-efficiency AC drain motors. Often incorporate filter traps to catch debris before it reaches the impeller. Top-Load Washing Machines May use simpler universal motors. Pump assembly may be integrated into the transmission housing in older designs. Compact or Portable Washers Low-power DC motors enhance energy efficiency while ensuring quiet, smooth operation in washing machines. Common Problems with Drain Motors Problem Possible Cause Symptoms Motor not running Electrical fault, blown fuse, faulty control board Machine won’t drain Loud noise during draining Damaged impeller, debris in pump housing Grinding or rattling sound Slow draining Clogged hose or filter Water remains in tub after cycle Leaks Worn shaft seal or cracked pump housing Water under machine Maintenance Tips for Long Motor Life Regularly clean the filter to avoid debris buildup. Check drain hoses regularly for any kinks or blockages. Run periodic cleaning cycles with descaling solution to prevent limescale buildup. Avoid overloading the machine, which can cause excess strain on the motor. Troubleshooting a Faulty Drain Motor Safety First Disconnect the washing machine from its electrical power source. Turn off the washing machine’s main water supply. Steps to Diagnose Check the Filter – Remove and clean any lint or debris. Inspect the Impeller – Check for any cracks, chips, blockages, or visible damage. Test Electrical Continuity – Check coil resistance using a multimeter for accurate measurement. Examine Wiring – Look for loose or corroded connectors. Replacement If the motor is faulty: Disconnect the wiring harness. Remove the mounting screws. Replace with a compatible OEM or high-quality aftermarket motor. Energy Efficiency and Modern Innovations Modern washing machines focus not only on effective water removal but also on energy savings and quiet operation. Brushless DC Motors Consume less electricity. Operate with less vibration and noise. Smart Control Integration Variable-speed draining based on water load. Self-diagnostic features to detect clogs or motor faults. Eco-Drain Technology Some premium washers reuse warm rinse water for the next wash cycle, requiring precise motor control to partially drain. Comparing Drain Motor Designs Feature Synchronous AC Universal Brushless DC Efficiency High Moderate Very high Noise Low Moderate Very low Durability High Moderate High Cost Moderate Low High Lifespan of a Drain Motor On average, a drain motor lasts 5–10 years, depending on: Usage frequency. Water quality (hard water shortens life). Maintenance practices. Signs of end-of-life include frequent clogging, overheating, and increased noise. The drain motor is a vital component that ensures

Electronically Commutated (EC) centrifugal fans have become a preferred choice for HVAC systems, data centers, air handling units, and cleanroom environments due to their energy efficiency, precise speed control, and compact design. While these fans already offer quieter operation than many AC alternatives, noise reduction remains a critical engineering priority—especially in applications where comfort, productivity, or compliance with environmental noise regulations is essential. Fan noise can affect human comfort, disrupt sensitive equipment, and even contribute to long-term hearing damage in high-intensity industrial environments. Therefore, integrating noise reduction technologies into EC centrifugal fan design is not just a performance enhancement—it is a necessity. Noise Sources in EC Centrifugal Fans Before applying noise control solutions, it is essential to first determine the sources of fan noise. In EC centrifugal fans, noise is typically categorized into aerodynamic, mechanical, and electrical sources. Aerodynamic Noise Blade Passing Frequency (BPF): Caused by blades cutting through the air, creating pressure fluctuations. Turbulence: Generated by airflow separation, vortex shedding, and wake interactions. Inlet and Outlet Disturbances: Poor duct design can cause additional turbulence and noise. Mechanical Noise Bearing Noise: Friction and imperfections in bearings generate vibration and tonal noise. Structural Resonance: Fan housings and mounts can amplify mechanical vibrations. Electrical Noise Motor Commutation: Although EC motors use electronic commutation, switching transients can produce high-frequency tonal noise. Electromagnetic Vibration: Interaction between magnetic fields and rotor/stator components may cause audible hum. Key Parameters Affecting Noise in EC Fans Understanding the parameters influencing noise generation helps in selecting the right noise reduction strategies: Parameter Influence on Noise Blade Design Shapes airflow, affects turbulence and tonal components Tip Clearance Impacts vortex formation and high-frequency noise Fan Speed Higher speed increases both tonal and broadband noise Housing Geometry Poor design increases flow separation and turbulence Motor Control Method Switching frequency impacts tonal electrical noise Aerodynamic Noise Reduction Technologies Optimized Blade Profiles Using airfoil-shaped blades reduces turbulence and increases aerodynamic efficiency. Today’s CFD technology enables engineers to: Minimize stall points. Reduce flow separation. Smooth pressure gradients across the blade. Example: Some EC centrifugal fans use backward-curved blades with optimized curvature to reduce vortex shedding. Blade Count and Spacing Adjustments Altering blade number changes the blade passing frequency, potentially moving tonal peaks away from sensitive frequency ranges. Uneven blade spacing can spread noise energy across multiple frequencies, making it less perceptible. Diffuser and Guide Vanes Guide vanes straighten airflow after the impeller, reducing swirl and turbulence at the outlet. This minimizes broadband noise and improves static pressure recovery. Inlet and Outlet Design Improvements Bellmouth inlets smooth the air entry, reducing turbulence at the leading edge. Flared or aerodynamic outlets help maintain laminar flow, lowering noise from sudden expansion. Mechanical Noise Reduction Technologies High-Precision Bearings Low-noise, high-quality ball or sleeve bearings with optimized lubrication reduce friction-induced noise. Some EC fan manufacturers use ceramic hybrid bearings for lower vibration. Vibration Isolation Mounts Rubber, silicone, or spring mounts reduce structure-borne vibration transmission. Particularly effective when fans are mounted in rigid HVAC frames. Structural Damping Applying damping materials (e.g., constrained layer damping sheets) to the fan housing reduces resonance amplification. Electrical Noise Reduction Technologies High-Switching-Frequency Drives Increasing PWM (pulse-width modulation) switching frequency above the human audible range (>20 kHz) eliminates tonal switching noise. Sinusoidal Commutation Replacing traditional trapezoidal commutation with sinusoidal control smooths torque ripple, reducing both mechanical vibration and audible electrical hum. Shielding and Filtering Electromagnetic shielding and proper grounding reduce radiated electrical noise that can be picked up acoustically by other components. Acoustic Treatment Technologies Sound-Absorbing Materials Acoustic foams inside the fan enclosure absorb high-frequency noise. Fiberglass or mineral wool liners in ducts reduce broadband noise. Silencers and Attenuators Reactive silencers target tonal noise using resonators. Dissipative silencers reduce broadband noise via absorption. Enclosures and Acoustic Barriers Placing fans inside an acoustic enclosure with soundproofing materials can drastically reduce radiated noise, though it must be balanced with cooling requirements. Active Noise Control (ANC) in EC Fans ANC systems use microphones, speakers, and digital processors to generate anti-phase sound waves that cancel unwanted noise. While more common in duct systems than individual fans, ANC can: Target specific tonal frequencies (e.g., blade passing frequency). Reduce low-frequency noise that passive materials struggle to absorb. Control Strategy Optimization Since EC motors offer precise speed control, intelligent fan speed management can be a noise reduction strategy: Variable Speed Operation: Reducing fan speed during low load periods decreases aerodynamic and mechanical noise. Soft Start/Stop: Gradual acceleration and deceleration reduce transient noise spikes. Load Matching: Avoiding operation near resonance frequencies improves overall noise performance. Measurement and Validation Noise reduction strategies must be verified through acoustic testing: Test Type Purpose Sound Power Level (SWL) Determines total acoustic energy output Sound Pressure Level (SPL) Measures perceived loudness at specific locations Frequency Spectrum Analysis Identifies tonal peaks and broadband noise content Vibration Analysis Detects mechanical resonance sources Testing should be conducted in accordance with ISO 3744 (free-field over a reflecting plane) or ISO 5136 (ducted fan noise measurement). Real-World Application Examples Case Study 1: Data Center Cooling A large data center reduced cooling fan noise by: Switching from AC to EC centrifugal fans with backward-curved blades. Adding inlet bellmouths and duct silencers. Increasing PWM frequency to 25 kHz. Result: 7 dB(A) noise reduction and improved cooling efficiency. Case Study 2: Hospital HVAC A hospital air handling unit integrated: Acoustic liners in ducts. Variable-speed EC fans with sinusoidal commutation. Vibration isolation mounts. Result: Noise level in patient rooms dropped below 35 dB(A). Comparative Effectiveness of Noise Reduction Methods Noise Source Technology Applied Typical Reduction (dB) Aerodynamic Optimized blade profile 2–5 Aerodynamic Inlet bellmouth + diffuser 3–6 Mechanical High-precision bearings + isolation 2–4 Electrical High-frequency PWM + sinusoidal control 1–3 Acoustic Silencers and duct liners 5–10 Active ANC (targeted tonal frequencies) 5–15 Future Trends in EC Fan Noise Reduction AI-Based Acoustic Optimization Machine learning models can analyze real-time noise spectra and adjust fan speed, blade pitch (in variable-pitch designs), or ANC parameters dynamically. Additive Manufacturing for Blade Design 3D printing allows highly complex blade geometries that improve aerodynamics

The global shift toward energy efficiency, precision control, and reduced maintenance costs has accelerated the adoption of Electronically Commutated (EC) centrifugal fans across industries. At the heart of these fans is the Brushless DC (BLDC) motor, a technology that merges the electrical efficiency of DC operation with the convenience of AC mains connectivity through integrated electronics. While centrifugal fans have long been powered by traditional AC induction motors, the introduction of BLDC motors into fan design has transformed performance possibilities. EC centrifugal fans now offer superior energy efficiency, lower noise, precise airflow control, and extended service life—attributes directly linked to BLDC technology. What is an EC Centrifugal Fan? An EC centrifugal fan is a fan that uses a brushless DC motor powered by an integrated electronic control module. The “electronically commutated” part means that instead of using mechanical brushes and a commutator to switch current in the rotor windings, the switching is done electronically via a control circuit. Key Points: Power Input: EC fans are connected to standard AC mains (single-phase 110–240V or three-phase 380–480V). Motor Operation: Internally, AC is rectified to DC and supplied to the BLDC motor windings. Speed Control: Controlled by pulse-width modulation (PWM), 0–10V analog signal, or digital protocols like Modbus or BACnet. Airflow Generation: The centrifugal impeller accelerates air radially outward, creating a pressure rise for ducted systems. Inside the BLDC Motor A Brushless DC motor inside an EC fan consists of: Stator – Laminated steel core with copper windings, forming the stationary part of the motor. Rotor – Permanent magnets mounted on a shaft, replacing rotor windings found in AC induction motors. Position Sensors – Detection of rotor position using Hall-effect sensors or through sensorless control algorithms. Electronic Controller (ECU) – Rectifies AC to DC, manages commutation, regulates speed, and controls torque. Rotor Uses rare-earth permanent magnets (typically NdFeB) for high magnetic flux density. No rotor copper windings → eliminates rotor I²R losses. Light rotor reduces rotational inertia for faster speed changes. Stator Wound with enamelled copper wire. Optimized slot fill factor for higher efficiency. Often designed with skewed slots to reduce cogging torque. Commutation Performed electronically rather than mechanically. Switches current in windings in sync with rotor position to maintain torque production. Two main methods: trapezoidal (block) commutation and sinusoidal commutation. Trapezoidal: Simple, good for cost-sensitive applications. Sinusoidal: Smoother torque, lower noise, ideal for HVAC fans. How BLDC Motors Work in EC Fans Power Conversion Path AC Input: From mains power supply. Rectification: AC is converted to DC using a diode bridge or rectifier. DC Bus: Filters and capacitors smooth DC voltage. Inverter Stage: High-speed switching (MOSFETs or IGBTs) generates 3-phase AC for the BLDC motor. Electronic Commutation: Controller adjusts phase timing based on rotor position feedback. Output Control: Matches fan speed to required airflow or pressure setpoint. Why BLDC Motors Excel in EC Centrifugal Fans Efficiency BLDC motors achieve 80–90% efficiency compared to 60–75% for equivalent AC induction motors. Reduced rotor losses and optimized winding design. Speed Control Smooth variable-speed control from 20% to 100% of rated speed. High part-load efficiency—important for HVAC systems with variable airflow demands. Noise Reduction Sinusoidal commutation minimizes torque ripple. Precise control reduces mechanical vibration and aerodynamic noise. Compactness Higher torque per volume allows smaller motors for the same output. Eliminates bulky external VFDs by integrating control electronics. Performance Comparison: AC Induction vs BLDC in Centrifugal Fans Parameter AC Induction Motor Fan BLDC Motor EC Fan Motor Efficiency 60–75% 80–90% Speed Control Range Limited without VFD Wide (integrated control) Torque at Low Speed Reduced Maintained Heat Generation Higher Lower Noise Level Higher at part load Lower due to smoother commutation Maintenance Bearings only Bearings only Power Factor 0.6–0.85 >0.95 Design Considerations for BLDC Motors in EC Fans Motor Sizing Must handle peak torque during startup and transient load changes. Oversizing slightly can improve thermal performance and extend lifespan. Thermal Management BLDC motors generate less heat, but integrated electronics require cooling. Common methods: heat sinks on controller housing, forced airflow from impeller. Magnet Selection NdFeB offers highest performance but can lose magnetism at high temperatures (>150°C). For high-heat applications, SmCo magnets may be used. Control Algorithms Field-Oriented Control (FOC) for optimal torque and efficiency. Sensorless control for lower cost, but Hall sensors often preferred for high reliability in HVAC. Integration with Fan Aerodynamics BLDC motors enable new aerodynamic optimizations in EC centrifugal fans: Direct-drive design eliminates belts and pulleys, improving mechanical efficiency. Lower rotor inertia allows adaptive speed changes to meet real-time airflow demands. Integration with variable inlet vanes or EC impeller blades for peak performance. Application Commercial HVAC Systems Fans for supply and return airflow in air handling units Demand-controlled ventilation with CO₂ or occupancy sensors. Data Centers Precise temperature and pressure control for server room cooling. EC fans integrated into Computer Room Air Conditioning units. Refrigeration and Cooling Towers Variable-speed fans reduce energy use during cooler ambient conditions. Improved defrost cycles. Cleanrooms & Laboratories Low-noise, precision airflow for controlled environments. Energy Savings Example Consider a 5 kW centrifugal fan running 6,000 hours/year: AC Induction Fan Efficiency: 70% Input = 7.14 kW Annual Energy Use = 42,840 kWh BLDC EC Fan Efficiency: 88% Input = 5.68 kW Annual Energy Use = 34,080 kWh Savings: 8,760 kWh/year (~$1,050/year at $0.12/kWh) CO₂ Reduction: ~6.2 metric tons/year (based on 0.7 kg CO₂/kWh grid emission factor) Reliability and Maintenance No brushes → no brush wear, less downtime. Bearings remain the only major wear component. Electronics are designed for 40,000–60,000 hour lifespans but require protection from moisture and surges. Industry Standards and Compliance BLDC-powered EC fans often meet or exceed: EU ErP Directive for fan efficiency. US DOE Fan Energy Index (FEI) requirements. ISO 5801 (airflow performance testing). IEC 60034-30-2 for motor efficiency classification. Future Trends Wide Bandgap Semiconductors (SiC, GaN): Improve inverter efficiency and reduce controller size. Sensorless High-Precision Control: For cost and reliability improvements. IoT Integration: Remote monitoring, predictive maintenance, real-time optimization. The Brushless DC motor is the technological backbone of EC centrifugal fans, delivering unmatched efficiency, control precision,

Centrifugal fans serve HVAC, industrial ventilation, clean rooms, electronics cooling, and various air-moving uses. They move air radially, changing its direction by 90 degrees and increasing its pressure. Traditionally, AC centrifugal fans—powered by alternating current induction motors—were the standard choice. However, in the last decade, EC (Electronically Commutated) centrifugal fans, which integrate a brushless DC motor with onboard electronics, have emerged as a high-efficiency alternative. Choosing between EC and AC centrifugal fans involves balancing performance, efficiency, cost, and application requirements. This article examines their differences in depth, providing data, examples, and recommendations. AC Centrifugal Fans Driven by asynchronous induction motors powered directly from the AC mains. Speed is determined by supply frequency (50 Hz or 60 Hz) and motor pole count. Speed control requires additional devices (e.g., VFDs or voltage regulators). Key Features: Simple, robust design. Long-established technology. Lower initial cost. EC Centrifugal Fans Use brushless DC motors with integrated AC-to-DC conversion electronics. Speed control is built-in and managed electronically. Motor commutation is handled via microprocessor-controlled electronics. Key Features: Higher efficiency. Integrated speed control. Precise airflow management. How They Work Feature AC Centrifugal Fan EC Centrifugal Fan Motor Type Induction motor (single or three-phase) Brushless DC motor with integrated electronics Power Supply Direct AC AC converted to DC internally Speed Control External (VFD, voltage regulator) Integrated electronic control Efficiency 50–70% (typical) 80–90% (typical) Maintenance Minimal, but higher wear over long term Very low, fewer wear parts Efficiency and Energy Consumption AC centrifugal fans have limited efficiency due to: Rotor slip losses in induction motors. Fixed speed operation. Lower power factor at partial load. EC centrifugal fans: Use permanent magnets → no rotor slip losses. Operate with variable speed and optimized control algorithms. Provides excellent efficiency across a wide range of operating conditions. Table 1: Typical Efficiency Comparison Motor Power (kW) AC Fan Efficiency (%) EC Fan Efficiency (%) 0.5 60 82 1.0 65 85 2.0 68 88 5.0 70 90 Energy Savings Example Consider a 2 kW fan running 4,000 hours/year: AC fan: 2 kW × 4,000 h ÷ 0.68 efficiency = 11,764 kWh/year EC fan: 2 kW × 4,000 h ÷ 0.88 efficiency = 9,091 kWh/year Annual Savings: 2,673 kWh/year, which could translate to $300–$500/year depending on electricity rates. Speed Control and Airflow Management AC Fans Speed changes require frequency inverters (VFDs) or voltage controllers. Each method adds cost and may introduce harmonic distortion. Mechanical dampers are an option but waste energy. EC Fans Built-in electronic control allows speed adjustment via: 0–10V control signal PWM signal Modbus or BACnet communication Allows dynamic adjustment for demand-based ventilation, leading to significant energy savings. Noise Performance AC fans operate at fixed speed, often generating more noise during low demand periods since airflow cannot be reduced without throttling. EC fans reduce noise by slowing down during partial load, cutting sound levels significantly. Table 2: Example Noise Levels Operating Mode AC Fan Noise (dB(A)) EC Fan Noise (dB(A)) Full Speed 75 74 70% Speed 75 (throttled) 66 50% Speed 75 (throttled) 60 Maintenance and Reliability AC Fans Consistent performance under tough industrial conditions. Bearings require periodic inspection/lubrication. Motor winding insulation can degrade over decades. EC Fans Fewer mechanical wear parts (no brushes). Electronics are the main wear point—quality design is crucial. Often have longer service intervals but can be more complex to repair. Cost Considerations Initial Purchase Cost AC centrifugal fans: 20–40% lower upfront price. EC centrifugal fans: Higher due to integrated electronics and permanent magnet motors. Lifetime Cost When factoring in energy savings and maintenance, EC fans often have a lower total cost of ownership (TCO). Example ROI Calculation (2 kW fan): AC Fan Cost: $1,000 EC Fan Cost: $1,400 Annual Energy Savings: $350 Payback Period: (1,400 – 1,000) ÷ 350 ≈ 1.14 years Environmental Impact EC fans contribute to: Lower CO₂ emissions due to reduced energy use. Compliance with efficiency regulations like EU Ecodesign Directive (ErP) or U.S. DOE fan efficiency rules. Applications and Suitability AC Fans: Best For Heavy-duty industrial settings where speed variation is not critical. Harsh environments where electronics may fail prematurely. Budget-sensitive projects. EC Fans: Best For Commercial buildings requiring variable air volume (VAV) control. Data centers, cleanrooms, and laboratories where precise airflow is critical. Energy-efficient retrofits to meet green building standards. Comparative Summary Table Factor AC Centrifugal Fan EC Centrifugal Fan Efficiency 50–70% 80–90% Speed Control External device required Integrated Noise Control Limited Excellent at partial load Maintenance Low to medium Low Initial Cost Low Higher TCO Higher (over lifetime) Lower (energy savings) Best Use Case Fixed-speed, industrial Variable-speed, efficiency-driven Real-World Example: Data Center Ventilation Upgrade A data center replaced 20 × 2 kW AC centrifugal fans with EC versions: Energy savings: 2,673 kWh/year/fan → 53,460 kWh/year total Annual cost savings: ~$8,000 (at $0.15/kWh) CO₂ reduction: ~25 metric tons/year Payback: 1.5 years Decision-Making Framework When choosing between EC and AC centrifugal fans, consider: Operating Hours – High operating hours favor EC fans for ROI. Airflow Variability – If demand fluctuates, EC offers more control and savings. Budget Constraints – AC may be better for short-term, low-cost installations. Environment – Harsh, high-temperature environments may still favor AC fans unless EC is specifically designed for such conditions. Regulatory Requirements – EC fans may be necessary to meet modern efficiency standards. Both EC and AC centrifugal fans have valid applications: AC fans remain reliable, cost-effective choices for fixed-speed, rugged industrial environments. EC fans shine in energy efficiency, noise reduction, and precision airflow control, making them ideal for commercial, residential, and high-tech facilities. If energy costs are significant and variable airflow is required, EC centrifugal fans almost always offer a better long-term investment. However, in cost-sensitive, fixed-speed industrial environments, AC centrifugal fans can still be the practical choice.

Axial flux motors (AFMs) offer exceptional torque density, a compact form factor, and high efficiency, making them ideal for electric vehicles, aerospace, industrial automation, robotics, and renewable energy applications. A critical design parameter in AFMs is the winding configuration—how the copper coils are arranged around the stator. Two dominant approaches are: Distributed winding (also known as lap winding or distributed armature winding) Concentrated winding (also called tooth-coil winding) The choice between these winding techniques has profound implications on: Motor efficiency Torque ripple Manufacturing complexity Thermal management Cost and weight Axial Flux Motor Winding In an axial flux motor: The stator contains coils that produce an alternating magnetic field when energized. Permanent magnets on the rotor interact with the field to generate torque. Unlike radial flux motors, axial flux motors feature a flat, disc-shaped design, with coil placement optimized for magnetic flux flowing axially.The winding configuration determines: Slot fill factor (how efficiently copper occupies slot space) Inductance and resistance of the coils Magnetic flux distribution Thermal dissipation efficiency Distributed Winding in Axial Flux Motors Definition In distributed winding, the coils are spread over multiple stator slots per pole per phase. Each phase winding is distributed across several slots, resulting in overlapping coil sides. Example: For a 12-slot, 10-pole motor, a phase winding may span several slots in a wave-like pattern. Characteristics Produces a sinusoidal magnetomotive force (MMF) distribution, reducing harmonic content. Higher copper usage compared to concentrated winding. More complex coil insertion and end-winding design. Advantages Low harmonic distortion → minimizes eddy current loss within the rotor magnets Lower torque ripple → smoother operation. Better efficiency at high speed due to reduced core loss from harmonics. Disadvantages Longer end windings → higher copper losses (I²R losses). Heavier and bulkier due to more copper. More complex manufacturing and winding insertion process. Concentrated Winding in Axial Flux Motors Definition In concentrated winding, each coil is wound around a single tooth or stator pole. The coil sides are concentrated on one tooth rather than distributed over several. Example: For a 12-slot, 10-pole motor, each tooth carries one complete coil. Characteristics Produces a more trapezoidal MMF waveform, increasing harmonic content. Shorter end windings, reducing copper length and weight. Easier manufacturing and coil replacement. Advantages Higher slot fill factor → better thermal dissipation and compact design. Lower copper usage → reduced resistance, less I²R loss. Simpler winding process → suitable for automated manufacturing. Disadvantages Higher torque ripple due to harmonic components. Higher AC copper losses at high speeds from increased harmonic currents. Requires additional design measures to control eddy current loss in magnets. Key Performance Metrics: Distributed vs Concentrated Table 1: Comparison of Distributed and Concentrated Winding in Axial Flux Motors Parameter Distributed Winding Concentrated Winding MMF waveform Sinusoidal (low harmonics) Trapezoidal (high harmonics) Torque Ripple Low Higher Copper Usage Higher (longer end windings) Lower (shorter end windings) Slot Fill Factor Medium High Efficiency at High Speed Higher Lower (due to AC losses) Manufacturing Complexity High Low Weight Higher Lower Thermal Management More challenging (dense winding) Easier (compact coil on single tooth) Cost Higher Lower Electromagnetic Impact of Winding Choice Harmonics and Losses Distributed winding minimizes slot harmonics, reducing iron and eddy current losses in rotor magnets. Concentrated winding increases harmonic content, leading to higher eddy currents, especially in surface-mounted permanent magnets. Efficiency Trends Test data for a 5 kW axial flux prototype: Winding Type Peak Efficiency (%) Torque Ripple (%) Copper Loss (W) Core Loss (W) Distributed 95.2 2.5 140 60 Concentrated 94.1 5.8 110 85 Thermal Management Considerations Distributed Winding More copper per slot → higher thermal mass, but longer end windings can be harder to cool. Requires advanced cooling: forced-air or liquid cooling channels in the stator. Concentrated Winding Shorter end windings and compact coils make cooling more direct. Easier to integrate direct winding cooling (DWC) systems. Manufacturing and Cost Implications Distributed Winding More labor-intensive due to overlapping coil placement. Ideal for limited runs prioritizing performance over cost Concentrated Winding Easier to automate with pre-formed coils. Preferred in mass production applications like electric two-wheelers, drones, and some EV motors. Application-Specific Recommendations Application Recommended Winding Reason High-performance EV traction Distributed High efficiency, low torque ripple Light electric vehicles (e-bikes) Concentrated Cost-effective, compact, easy to produce Aerospace actuators Distributed Precision motion, low noise Drones & UAVs Concentrated Lightweight, high torque-to-weight ratio Industrial automation Distributed Smooth motion, reduced mechanical vibration Portable tools Concentrated Low cost, simplified manufacturing Design Optimization Strategies For Distributed Winding: Use fractional-slot winding to further minimize torque ripple. Employ skewed slots to reduce cogging torque. Optimize end-winding shape to reduce copper loss. For Concentrated Winding: Apply magnet segmentation to reduce eddy current loss from harmonics. Use high-resistivity magnet materials (e.g., NdFeB with Dy additions). Incorporate fractional-slot concentrated winding (FSCW) to balance harmonic suppression and compactness. Case Study: EV Axial Flux Motor Motor Specs: Power: 100 kW Diameter: 320 mm Cooling: Liquid Distributed Winding Design: Efficiency: 96.2% peak Torque ripple: 1.8% Manufacturing cost index: 1.4 Concentrated Winding Design: Efficiency: 94.9% peak Torque ripple: 4.5% Manufacturing cost index: 1.0 For premium EVs, distributed winding is chosen for its smoothness and efficiency. For budget EVs, concentrated winding offers competitive performance at lower cost. The choice between distributed and concentrated winding in axial flux motors depends on performance priorities, cost constraints, and application needs: Distributed winding: Best for applications needing high efficiency, low torque ripple, and smooth operation, though at higher manufacturing cost. Concentrated winding: Ideal for cost-sensitive, lightweight, and compact designs, especially in mass production. Future innovations—like fractional-slot distributed winding and segmented magnet designs—are helping bridge performance gaps, allowing engineers to tailor winding configurations more precisely to application requirements.

Axial flux motors (AFMs), also known as pancake motors, offer distinct advantages over their radial flux counterparts—including high power density, compact form, and efficient thermal management. Central to their performance are magnet configurations, particularly in single-rotor and double-rotor designs. Understanding differences in magnetic layout, flux behavior, performance metrics, and trade-offs is essential to choosing the optimal configuration. Axial Flux Motor Basics Axial flux motors generate electromagnetic torque via interaction between permanent magnets (usually rare-earth) on a disc-shaped rotor and windings on a stator, typically sandwiching one or more rotor discs. Characteristics include: Compact axial length — resulting in higher torque density (Nm per liter) Short magnetic flux path — reduces magnetic losses and enables high efficiency Surface- or interior-mounted magnets — affects flux penetration and mechanical protection Magnet configurations influence: Flux density in the air gap (B_g) Cogging torque Thermal performance Mechanical complexity Key magnet layout types: Surface-Mounted Permanent Magnets (SPM) Interior Permanent Magnets (IPM) Halbach arrays (a specialized SPM array enhancing one-sided flux) Single Rotor Configuration In this design: One rotor disc bears magnets, typically facing a stator on one side. Commonly arranged as rotor–stator–[air gap]–housing. Magnetic Behavior Flux crosses a single air gap. Magnetic circuit simpler: one stator–rotor interface. Ease of manufacturing and assembly. Performance Characteristics Cogging Torque: Present; design mitigations like skewing or fractional slot winding help. Efficiency: High, but slightly lower than double-rotor due to single-sided flux utilization. Thermal Management: Easier—stator and windings accessible. Use Cases E-bikes, drones, appliances, low-cost industrial motors. Applications where thickness must remain minimal. Advantages Disadvantages – Simple design – Easier cooling – Lower cost – Lower torque density – One-sided flux only Double Rotor Configuration Two rotor discs, each with magnets, sandwich the stator in a rotor–stator–rotor (R–S–R) arrangement. Essentially, two flux paths operate in parallel. Magnetic Behavior Dual air gaps: one between each rotor and stator. Flux splits across two gaps; ideally symmetric to maximize utilization. Magnetic flux density can be higher for same magnet volume. Performance Characteristics Torque Density (T_d): Generally higher than single rotor, due to doubled interacting surface. Torque Calculation: Approximate torque scales near 2× single rotor (minus minor leakage losses). Cogging Torque: Can be reduced if rotor magnet poles are offset relative to each other or stator. Efficiency: Improved electrical-to-mechanical conversion due to better flux utilization. Complexity: Higher—requires supporting two rotors; mechanical alignment critical. Thermal Management: Slightly more complex due to sandwiched stator; but heat can flow from both sides to cooling surfaces. Use Cases Automotive traction motors (EVs/hybrid systems) Heavy-duty industrial drives Applications demanding high torque in limited axial space Advantages Disadvantages – Higher torque density – Better efficiency – Lower cogging – Higher cost – Complex alignment – Harder cooling Quantitative Comparison Below is a hypothetical comparative table based on typical small to medium-sized axial flux motors (e.g., 10 kW class), illustrating key metrics: Parameter Single Rotor (SR) Double Rotor (DR) Air Gap Count 1 2 Magnet Volume (V_magnets) 1 unit ~1.8–2 units* Peak Torque (Nm) 50 90 Torque Density (Nm/L) 45 80 Cogging Torque (% of T_peak) 5% 3% Efficiency (%) 93 95 Axial Length (mm) 100 150 Structural Complexity Low Medium-high Thermal Access Excellent Moderate Estimated Cost Index 1.0 1.3 (due to parts & assembly) DR requires more magnet material, but improved magnetic utilization may allow using slightly less per rotor than SR per rotor. Notes on Data: Magnet Volume: A double-rotor design uses more magnets, but each rotor can be slightly thinner if the flux paths share better, sometimes resulting in ~1.8× rather than a full 2× increase. Torque Density: DR yields ~1.8× to 2× the torque, reflecting two active faces. Cogging: Offset magnet arrangement mitigates torque ripple better in DR. Efficiency: Gains derive from reduced magnetic leakage and better utilization—typically 1–2 percentage points. Axial Length: DR is thicker, impacting form factor. Cost: Higher due to more rotor parts, dual bearings, more complex assembly. Design Considerations and Trade-offs Magnet Usage & Material Cost Rare-earth magnets (e.g., NdFeB) dominate cost. DR uses more magnets, increasing cost—but higher performance may justify it. Designers often balance magnet grade (remanence, coercivity) and volume. Mechanical Complexity SR: single shaft and rotor assembly, simpler bearings and alignment. DR: requires two rotors, careful axial concentric alignment, often double bearings or a thrust bearing. Structural Support & Stiffness DR’s additional rotor adds weight and potential flex. Housing must be robust to sustain torque and axial forces. Cooling & Thermal Path SR: stator typically on exterior, easy to cool. DR: stator is in the middle—an internal stator requires heat paths both sides, often using cooling plates or fluid channels. Magnetic Design Complexity Flux cancellation and leakage must be controlled. Cogging reduction strategies: skewing, fractional slots, magnet angular offset (especially effective in DR by anti-phase rotor placement). Control Strategy Both use typical control (e.g., field-oriented control), but DR may have symmetric inductance profiles aiding smoother control. Applications and Case Examples Electric Vehicles and Traction Double Rotor AFMs excel where axial space exists (e.g., between output shaft and chassis). Example: A 50 kW DR AFM used in an EV delivers high torque density—peak 300 Nm in a 180 mm thick motor pack. Aerospace and Drones Single Rotor AFMs favored in lightweight, thin packages (e.g., propeller-driven drones). Example: A 5 kW pancake motor, diameter 200 mm, axial length 60 mm, weighing 2 kg—suitable for multicopter propulsion. Industrial Automation Both types used for servo motors or direct-drive applications. DR proves advantageous in limited axial envelope but high torque need (e.g., robotic joints). Simulated Performance Modeling Consider two simulated 20 kW motors for a robotics application: SR Model: Diameter: 250 mm Axial length: 90 mm Magnet volume: 0.005 m³ equivalent Simulated flux density (B_g): 0.8 T Peak torque: ~200 Nm Estimated efficiency: 93% DR Model: Same diameter Axial length: 140 mm Magnet volume: 0.0085 m³ equivalent Simulated B_g per side: 0.75 T Peak torque: ~350 Nm Estimated efficiency: 95% Key insights: DR achieves about 1.75× torque increase for ~1.7× magnet volume increase. Efficiency gain of ~2 points likely due to improved flux utilization and