Outrunner Brushless Motors- Suzhou Retek Electric Technology Co., Ltd.

Outrunner BLDC Motor Configuration and Mechanics

Outrunner motors are characterized by their rotating external shell (the "can"), which contains the magnets, while the stator (with the windings) remains fixed on the central shaft. This design results in a larger rotor diameter compared to inrunner motors of similar size, placing the magnets further from the central axis. This increased radius (lever arm) fundamentally translates to a significantly higher torque constant (Kt) and greater moment of inertia, making them well-suited for direct-drive applications without the need for high-ratio gearboxes. They typically operate at lower Kv values and lower nominal speeds than inrunners, focusing on force generation rather than high rotational speed. Their open structure often facilitates natural air cooling.

Focus Area: High specific torque, efficiency at low Kv, and suitability for direct drive.
Key Technology: External rotating rotor design maximizing the electromagnetic radius for torque generation.
Characteristic: High pole count, large air gap diameter, and high moment of inertia.
Efficiency Point: Optimized for peak efficiency at medium loads and low-to-medium speeds.

Introduction

Detailed Parameters and Performance Data

Introduction to Direct Drive Outrunner Solutions

When mechanical simplicity, high torque at moderate speeds, and an excellent power-to-weight ratio are the primary driving factors, the outrunner architecture offers significant advantages. Retek Electric Technology (RTK) utilizes the robust mechanical structure of the outrunner to deliver propulsion and actuation systems that are inherently simple, rugged, and efficient. As a specialized manufacturer, we focus on maximizing the magnetic efficiency within the large-diameter rotor structure, primarily serving sectors like multirotor UAVs, heavy-lift drones, and specialized industrial direct-drive systems where high reliability and simplified maintenance are critical. Our LN and WO series outrunners exemplify this dedication to high force output and minimal energy loss.

Applications

Advanced Technology Highlights

Key Application Areas

Heavy-Lift and Long-Endurance UAVs/Drones: Primary propulsion systems requiring high static thrust force and maximum flight duration (e.g., LN6215, LN8313, LN10018 series).
Electric Mobility (Direct Drive): Wheel hub motors for electric bicycles, scooters, and direct belt drives requiring high starting torque and continuous hill climbing force.
Robotics Actuation (Limbs/Joints): Direct drive for certain high-torque robotic joints where the size of the motor is acceptable and minimizing backlash from gearboxes is paramount.
Large Industrial Fans/Blowers: Direct-drive cooling fan motors and high-volume air movers where the low Kv prevents the need for large pulleys.
Gimbal and Camera Stabilization: Professional systems requiring high torque to maintain precise position against high inertial or external forces.
Linear Actuators: Driving mechanisms for industrial linear motion stages.

Technical Specifications

Industrial & Commercial Usage

Selected Motor Specifications

Specifications highlight the low Kv and high thrust capabilities typical of outrunner designs.

Parameter	Example LN5313 (Medium-Lift UAV)	Example LN13720 (Heavy-Lift UAV)
Outer Diameter (mm)	59	137
Kv Rating (RPM/V)	320 / 350 / 380	34 / 38
Max Thrust (kg)	Up to 2	Up to 15
Voltage Compatibility (S LiPo)	6S - 8S	12S - 24S
No-Load Current (A)	<2.5	<5.0
Magnet Count (Poles)	24 or higher	42 or higher

Additional Information

Supplementary Details & Notes

Manufacturing Process and Customization Services

Our production focuses on precision balancing, thermal management, and robust construction for outrunners:

Ultra-Fine Dynamic Balancing: Every outrunner can is dynamically balanced to extremely tight G-level tolerances (e.g., G2.5 or G1.0) to prevent destructive vibration and ensure bearing longevity at all operating speeds.
High-Temperature Bonding: Magnets are bonded using specialized high-temperature, aerospace-grade epoxies that maintain adhesion stability even under prolonged high-current operation and high heat.
Environmental Protection: Options for IP54 or IP55 sealing, including conformal coating of the stator windings and sealed bearings, are available for motors used in outdoor or marine environments.
Mounting Hole Patterns: Custom base plate, mounting hole dimensions, and specialized anti-vibration mounting systems can be accommodated to match specific airframe or chassis requirements.
Harness and Connector: Provision of high-strand-count silicone wire and custom connector types (e.g., MR30, XT90, AS150) rated for the required peak current.

Service & Support

Operational Benefits and Design Integrity

Superior Specific Torque: The large diameter and high pole count configuration provides an exceptional torque-per-ampere ratio (Kt), optimizing battery utilization.
Self-Cooling Mechanism: The spinning outer housing is actively designed with ventilation slots to function as a natural fan, providing efficient passive and forced cooling, thus increasing continuous power handling.
Mechanical Simplicity: The direct-drive nature minimizes components, leading to reduced system complexity, fewer potential failure points, and simplified maintenance.
High Reliability: Robust construction utilizing large bearings to manage the inertial forces and the external load (e.g., propeller, wheel).
Battery Voltage Versatility: Offered in both low-voltage, high Kv variants (for RC/consumer) and high-voltage, low Kv variants (for industrial/heavy-lift).

Frequently Asked Questions

Q: Why are outrunners typically used in drones, specifically heavy-lift models?
A: Heavy-lift drones require maximum thrust from large propellers operating at relatively low RPM. The outrunner's low Kv and high Kt allow it to efficiently drive these large props directly, minimizing the weight and complexity associated with multi-stage gearboxes.

Q: What is the maximum safe operating speed for an outrunner motor?
A: Operating speed is limited by the centrifugal force on the magnets and the structural integrity of the can. Generally, outrunners are limited to below 10,000 RPM for larger sizes (D>80mm) and up to 20,000 RPM for smaller, lighter designs.

Q: How do you prevent the magnets from detaching from the can at high speed?
A: We use a combination of high-strength, temperature-resistant epoxy (e.g., Loctite type) to bond the magnets to the can and, in some high-speed models, an internal reinforcing sleeve or ring to contain the magnets against centrifugal force.

Q: Are outrunners susceptible to foreign object damage (FOD)?
A: Yes, due to their exposed, spinning outer casing, they are more vulnerable to FOD than sealed inrunners. Our industrial outrunners often feature protective screens or partial enclosures to mitigate this risk.

Resources

Component Material Selection and Impact

Material considerations specific to outrunner structure:

Outer Casing (Can): High-strength, aerospace-grade aluminum alloys (7075 or 6061 T6) are used to minimize mass while ensuring structural integrity against centrifugal stress.
Rotor Magnets: High-energy Neodymium magnets are strictly chosen and precisely balanced. Thermal management materials (e.g., heat-resistant coatings) are crucial for high-power models.
Stator Laminations: Very thin (0.2 mm or less) silicon steel laminations are used to minimize eddy current losses, which are more pronounced in high-pole-count designs.
Bearings: Oversized, sealed deep groove ball bearings (e.g., EZO or NSK grade) are specified to handle the increased radial and axial loads from large loads (propellers, wheels).

About Suzhou Retek Electric Technology Co., Ltd.

Unlike other motor suppliers, Retek engineering system prevents the selling of our motors and components by catalogue as every model is customized for our customers. The customers are assured that every component they receive from Retek is designed with their exact specifications in mind. Our total solutions are a combination of our innovation and a close working partnership with our customers and suppliers.

As China Outrunner Brushless Motors Manufacturers and Wholesale Outrunner Brushless Motors OEM/ODM Suppliers, Retek business consists of three platforms: Motors, Die-Casting and CNC manufacturing and wire harness. Retek products are widely supplied for residential fans, vents, boats, airplanes, medical facilities, laboratory facilities, trucks and other automotive machines.

Welcome to send us an RFQ, it is believed you will get the best cost-effective products and services here!

Customized Solutions

Quality Assurance

Global Export

Suzhou Retek Electric Technology Co., Ltd.

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