Self-Cooling Technology
Heat significantly reduces the efficiency and operating life of a motor. Brushless motors typically operate cooler than conventional brushed motor due to the elimination of commutator/brush friction. Common to both BLDC and Brushed motors is the presence of copper magnet wire coils found on the stator or armature. When electrical current passes through these coils a magnetic field is generated allowing for the rotor to operate. Heat is generated in the copper coils due to electrical resistance. In addition, high ambient temperatures increase electrical resistance in the stator’s copper windings, requiring more electricity to generate the same magnetic field. The increased electrical current generates even more heat. This creates a potential of thermal runaway, where the increase in temperature causes a further increase in temperature, leading to burnout of the coils and destruction of the motor and other critical components. The permanent magnets found in the motor reduce their magnetic flux at high temperatures. In addition, at very high temperatures, or the magnets curie temperature, the magnet will start to demagnetized. After the temperature drops below this value, it will not behave as it did before it reached that temperature. The stator will need to consume more electrical current producing a stronger magnetic field to off-set the weaker magnets. Reducing the permanent magnets magnetic strength decreases the efficiency of the motor and adds to the probability of thermal runaway. Adequate cooling is critical to maintain the motor's high efficiency and curtailing thermal runaway from destroying critical components.