Brushless Electric Motors

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Brushless Motors

General:
Brushless motors are more powerful, durable, and efficient than brushed motors of the same size. Used in your radio controlled airplane, boat, or car, they can generate more power with longer run times.

What Is The Difference Between a Brushless Motor and Brushed motor?:
A brushed motor uses stationary metallic contacts that 'brush' against moving metallic contacts. These 'brushes' are used to transfer electrical energy to coils on the rotating armature. A brushless motor consists of stationary coils and a rotating magnet that is connected to the output shaft. The coils are grouped together into phases, and an electronic motor controller powers up each coil in sequence, causing the magnet to rotate.

RPM, Kv, And Current Rating:
RPM stands for the number of rotations per minute, and signifies how fast a motor spins. Brushless motors are given a Kv rating, which is RPM per volt, that lets you determine how fast that motor will rotate with a given voltage supplied to it. A 980Kv motor powered by an 11.1V battery would spin at 980 x 11.1 = 10878 RPM with no load. The current rating specifies the maximum continuous and/or burst current that the motor is able to handle. When selecting a battery and speed control, choose ones with continuous current ratings equal to or greater that that of the motor.

Inrunner Vs Outrunner:
An inrunner motor has stationary coils which surround the rotating magnet at the center. An outrunner motor has stationary coils at the center, and the rotating magnet on the outside. Outrunner motors generally have lower Kv ratings, meaning they run at a lower speed, but with more torque, which would allow you to direct drive larger props without needing a gearbox. Most RC cars and boats would require an inrunner brushless motor.

Which Motor Is Best For My Plane?:
Most airplane manufacturers will recommend certain brushless motors for different models. However, if this is not specified, a good starting point would be to check what other people are using locally, or search the web. We frequently visit RCGroups, RC Universe, and WattFlyer to see what the RC communities are using. If you have a brushed motor that you are replacing, choose a brushless motor that is the same physical size, and uses about the same wattage. To determine the wattage, multiply the current your old motor draw by the voltage it is run at.