5 Key Facts You Need to Know About the Inrunner Brushless Motor

5 Key Facts You Need to Know About the Inrunner Brushless Motor

1. What Is an Inrunner Brushless Motor?
An Inrunner Brushless Motor is a type of brushless DC (BLDC) motor where the rotor is located inside the stator. This design results in a smaller rotating mass compared to an outrunner motor, enabling higher RPM, more stable operation, and greater mechanical precision.
Inrunner motors are widely used in applications where speed, efficiency, and compact design are critical—such as drones, RC cars, underwater thrusters, and industrial automation.

2. How the Inrunner Design Improves Performance
The unique structure of an Inrunner Brushless Motor offers several technical advantages:

• High Rotational Speed – Because the rotor diameter is smaller, the motor can achieve higher RPM without excessive centrifugal forces.

• Reduced Rotor Inertia – Less mass in the rotor means faster acceleration and deceleration, improving responsiveness.

• Better Cooling – The stationary outer shell (stator housing) makes it easier to integrate cooling systems like water jackets or heatsinks.

• Compact and Lightweight – Ideal for designs where space is limited but performance cannot be compromised.

• Precision Control – Especially in sensored versions, the motor can deliver smooth startup and accurate position control.

3. Voltage, Power, and Speed Options
Modern Inrunner Brushless Motors are available in a broad range of specifications to match different applications:

• Voltage: Common ratings include 12V, 24V, 36V, 48V, and even up to 96V for heavy-duty systems.

• Power: Small-scale models can be as low as 30W for micro devices, while high-performance models can exceed 10kW for industrial or marine use.

• Speed (RPM): Popular options range from 1,000 rpm for torque-focused applications to over 8,000 rpm for high-speed propulsion systems.

• Sensor Types:

  • Sensored: Uses Hall sensors for precise low-speed control, smooth acceleration, and instant start-up.

  • Sensorless: Simpler design, reduced cost, and suitable for applications where startup load is minimal.

• Protection Levels: Many models include waterproof or dustproof ratings (e.g., IP68) for harsh environments.

4. Applications of Inrunner Brushless Motors
Thanks to their efficiency and versatility, inrunner motors are used across multiple industries:

• Electric Propulsion – From small RC boats to large underwater scooters, the waterproof high-power models provide reliable thrust.

• Aerospace & UAVs – High-RPM, lightweight motors are ideal for drones that require quick responsiveness and stable flight.

• Industrial Automation – Used in conveyor systems, CNC machines, and robotic arms for precision motion control.

• Medical Devices – Compact, low-noise motors power equipment like surgical tools and diagnostic devices.

• Sports & Recreation – Electric surfboards, e-skateboards, and other personal mobility devices rely on inrunner motors for smooth acceleration and durability.

5. Choosing the Right Inrunner Brushless Motor
Selecting the right motor involves balancing your application’s speed, torque, size, and environmental requirements. Here are some guidelines:

1. Match Voltage and Power to Your Application

   • Low voltage (12–24V) and low power (50–500W) for small tools and hobby devices.

   • Medium voltage (36–48V) for mid-size robotics and mobility systems.

   • High voltage (60V+) and high power (1–10kW) for marine propulsion, heavy machinery, or industrial equipment.

2. Consider RPM and Gear Reduction

   • High RPM motors (6,000–8,000 rpm) excel in speed-focused tasks.

   • Lower RPM motors can be paired with gearboxes for high torque output.

3. Sensor Type

   • Choose sensored for applications requiring precision and smooth low-speed performance.

   • Choose sensorless for simpler, high-speed applications without heavy start-up loads.

4. Environmental Protection

   • For wet, dusty, or corrosive environments, look for waterproof ratings (e.g., IP68) and corrosion-resistant materials.

Real-World Example
A 3,000 rpm, 12V sensored inrunner motor from Brushless.com can power a compact medical centrifuge with smooth startup and accurate speed control. On the other end of the spectrum, a 6,000 W waterproof inrunner motor can drive an electric surfboard at high speed without overheating or water ingress.

Why This Information Matters
This guide draws on engineering principles, real-world usage data, and established motor design theory to ensure accuracy and reliability. Whether you are an engineer designing a propulsion system or a hobbyist upgrading an RC boat, understanding the core characteristics of an Inrunner Brushless Motor helps you make informed purchasing and design decisions.

Conclusion
The Inrunner Brushless Motor stands out for its compact size, high RPM capability, efficient cooling, and precise control. Available in a wide range of voltages, powers, and protection levels, it can be tailored to nearly any application—from delicate medical devices to high-powered marine propulsion.
When selecting your motor, consider your required torque, speed, voltage, sensor type, and environmental conditions. By doing so, you’ll ensure that your system performs efficiently, reliably, and for the long term.