To make operation more reliable, efficient and reduce noise, brushless DC motors have recently become popular, which are lighter and have the same energy output compared to brushed motors. Conventional brushed DC motors wear out over time and may spark, so brushed DC motors should not be used for long-term reliability-critical operations.
The rotor of the brushless DC motor is a permanent magnet, and its stator is a coil device. When the direct current passes through the coil, the energized coil becomes an electromagnet. The operation of brushless DC motors relies on the simple interaction of forces between permanent magnets and electromagnets. The specific process is as follows: After the coil is energized, the rotor with opposite magnetic poles rotates toward the stator due to magnetic attraction. The coil is energized when the rotor is close to the coil, the coil is energized when the rotor is close to the coil, and then the coil is energized with opposite polarity. This process is repeated so the rotor can continue to spin.
For a humorous analogy to aid memory, imagine a brushless DC motor running like the donkey and carrot story. The donkey tried his best to eat the carrot, but the carrot kept moving forward and the donkey couldn't reach it. While the motor works this way, it has a downside. You can see that only one coil is energized at any one time. Those two quiescent coils greatly reduce the power output of the motor. There is a trick to solve this problem, when the rotor is turned to this position, the coils behind the rotor can be energized when the first coil attracts the rotor, so that the coils behind the rotor will repel the rotor to turn forward. At this moment, the same polarity current generates more torque and more motor output power through the second coil combined effect. The combined force can also ensure that the brushless DC motor can have more continuous and stable torque. Because of this structure, the two coils have to be energized separately. With a slight modification of the stator coils, we can simplify the process by simply connecting the free ends of the two coils.
When energizing between the coil and the coil, we pay attention to the current flow between the coils, like a separate energized state, this is the working principle of the brushless DC motor, but you may have some interesting questions, how do I know to let The specific time each stator coil is energized? How do I know when to apply power to make the motor spin continuously? In order to achieve this effect in the brushless DC motor we use an electronic controller. First, a sensor is used to determine the rotor position. Based on the feedback position information, the controller decides which coil should be energized. General Hall effect sensors are most commonly used here. So far we have been talking about brushless DC motors with external transformation. Internal rotation brushless DC motors can also be seen in the market. We hope to have given you a good introduction to brushless DC motors.
