RC Plane Electric Motors and Speed Controls
Brushed RC Motors
As the name implies, Brushed Electric Motors utilize brushes in there operation. Current passes through soft blocks of material called brushes to the spinning commentator. Friction from this contact causes wear, requiring brush replacement at regular intervals. These motors are now being replaced in rc aircraft with much more efficient and maintenance free Brush less Motors.
Brush less RC Motors
Brush less motors have being developed that have the capacity to compete and even out perform there glow and gas counterparts.
With no brushes creating friction, brush less motors have a large gain in efficiency, allowing them to operate in the 80 to 90 percent efficiency range.With the leaps in technology almost daily these motors are getting smaller with more power with ever increasing efficiency numbers.
Both Brushed and Brush less Motors require speed controls to operate within the rc aircraft environment.
Each Speed Control is unique to either brushed or brush less types, these also need to be size matched as well. Example a motor requiring 20 amps of power to operate will require a speed control capable of delivering 20 amps of power. The power source, normally a battery in rc airplanes must also have the ability to delivery the required power.
BEC (battery eliminator circuit)
Some speed controls include a BEC circuit that reduces the battery voltage down to the voltage required by the rc receiver and servo's, thus eliminating the need for a separate receiver battery.
WARNING Almost all Electric Motors used in RC Aircraft operate on voltages higher than the receiver and servo's can tolerate. Never connect the motor power battery direct to the receiver or servo's.
Always connect through a bec circuit, voltage regulator or use a appropriate sized receiver battery.
Here is a excellent article in pdf format by Greg Covey's that has some excellent tips and resources to size electric gear for rc airplanes.