The Differences Between Outrunner and Inrunner Brushless Motors

Brushless motors have revolutionized the world of RC cars, planes, and drones. These efficient motors offer an incredible power to weight ratio compared to brushed motors, and they require little maintenance while providing longer run times. Two main types of brushless motors are available, outrunner and inrunner brushless motors. In this article, well explore the differences between outrunner and inrunner brushless motors.

What Are Brushless Motors?

Before we begin exploring outrunner and inrunner brushless motors, lets first understand what brushless motors are. Unlike brushed motors that use brushes to supply power to the motors rotating commutator, brushless motors use a controller to regulate the electricity supply to the motors coils. The controller monitors the motors position and adjusts the supply voltage to enhance the motors performance.

Brushless motors are more efficient, have a longer lifespan, and deliver more power than brushed motors, making them ideal for high-performance applications.

Outrunner Brushless Motors

Outrunner brushless motors feature an outer rotor design, which means that the motors stator is located in the center of the motor, and the rotor surrounds the stator on the outside. These motors typically have a larger outer diameter and a lower Kv rating than inrunner motors, which makes them well-suited for low-speed, high-torque applications such as multirotor applications.

Outrunner motors offer good heat dissipation, making them ideal for high RPM applications where heat buildup can damage the motor. They also provide a higher moment of inertia, which results in smoother, more stable operation.

Inrunner Brushless Motors

Inrunner brushless motors feature an inner rotor design, which means that the motors stator is located on the outside of the motor, and the rotor is located on the inside. These motors typically have a smaller outer diameter and a higher Kv rating than outrunner motors, which makes them well-suited for high-speed applications such as RC cars, planes, and helicopters.

Inrunner motors feature a low moment of inertia, which allows them to respond quickly to changes in the motors RPM. They also offer high power-to-weight ratios, making them ideal for high-performance applications.

Differences Between Outrunner and Inrunner Brushless Motors

Now that weve explored the basic differences between outrunner and inrunner brushless motors lets dive into more details. Here are the key differences between these two types of brushless motors:

1. Design

One of the most noticeable differences between outrunner and inrunner brushless motors is their design. Outrunner motors feature an outer rotor design, while inrunner motors feature an inner rotor design.

2. Kv Rating

The Kv rating is a measure of how many revolutions per minute (RPM) the motor will turn per volt applied. Outrunner motors typically have a lower Kv rating, which means that they generate more torque at lower speeds. Inrunner motors typically have a higher Kv rating, which means that they generate more RPM at a given voltage.

3. Size

Outrunner motors are typically larger than inrunner motors, which gives them a larger moment of inertia. Inrunner motors are smaller and more compact, making them well-suited for applications where space is limited.

4. Heat Dissipation

Outrunner motors feature good heat dissipation, which makes them ideal for high RPM applications where heat buildup can damage the motor. Inrunner motors, on the other hand, can generate more heat, which requires additional cooling to prevent damage.

5. Performance

Outrunner motors are well-suited for low-speed, high-torque applications, while inrunner motors are ideal for high-speed applications. Each type of motor has its strengths and weaknesses, and the best choice depends on the application.

Final Thoughts

While both outrunner and inrunner brushless motors offer excellent performance, they are designed for different applications. Outrunner motors are ideal for low-speed, high-torque applications such as multirotor drones. Inrunner motors are well-suited for high-speed applications such as RC cars, planes, and helicopters. Understanding the differences between outrunner and inrunner brushless motors will help you choose the right motor for your application and achieve optimal performance.

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Many of the TECHNOLOGY listed here can be purchased for less money, but in general we recommend paying a slightly higher price for significantly improved performance. These are our top choices and their recommended configurations.