Brushless motors offer several advantages to the modeler. First, there is less radio noise generated to interfere with the remote control. This will increase the reliability of the remote control and extend the operating distance. Second, when a brush motor spins fast, the brushes will tend to "fly" over the commutator, causing arcing and heating, thus lowering efficiency. Third, the effective resistance of the brushes is much higher then that of the MOSFETs that are electronically commutating a brushless motor, especially at high currents and temperatures. Foremost, brushless motors can fit much more copper inside (thicker wires) than a brush motor of equivalent size, thus lowering resistance, increasing efficiency, and increasing torque. Because of these facts, brushless motors have the inherent capability to spin faster and operate at higher currents, to produce more power, without the performance deteriorating. Since all the commutation of the motor is done electronically, the overall reliability of the system is much higher. The goal of any motor designer is to maximize efficiency in a motor without sacrificing performance. The energy from your battery is used up in two ways: kinetic (moving the load) and heat (friction and I2R losses). High power brush motors tend to have high frictional losses due to their large brushes and high spring forces, which are necessary to handle high currents. Brushless motors do not suffer from these frictional losses. Greater efficiency due to more copper and less resistance means more energy goes into kinetic and less into heat. This extra energy can either extend running time or increase power output. Since motor efficiency is largely dependent on the volume of copper (amount of wire inside) in the motor, brushless motors yield much better performance than a brush type motor of the same size because more copper can be packed on the outer radius of the brushless motor than on the inner radius of a brush motor. This allows a thicker gauge wire to be used. The windings run cooler because they have a direct thermal transfer to the case. This increases efficiency because copper has a lower resistance at lower temperatures. This allows a much higher peak and continuous output than a brush motor of a similar size because there is less danger of over heating. The magnets also stay cooler because the heat is radiated outward, away from the magnets. Also, the lower rotating mass allows the motor to spin up faster because of the lower inertia. |
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