Brushless motor (BLDC motor) is widely used in many fields, such as power tools, electric vehicles, home appliances and industrial automation, due to its high efficiency and low maintenance. Unlike traditional brushed motors, brushless motors have no brushes and commutators and rely on electronic controllers for commutation to ensure the smooth operation of the motor. In order to accurately control the speed and position of brushless motors, position sensors are required to provide feedback information. X-TEAM will briefly introduce the position sensor of brushless motors and its working mechanism.
- The role of position sensor
The main function of the position sensor of brushless motor is to detect the position of the rotor in real time and feedback the position to the motor control system. Based on the position of the rotor, the control system can accurately control the power-on sequence of the stator winding to achieve smooth operation of the motor. Motors without position sensors usually rely on back electromotive force (Back EMF) to estimate the rotor position, but the accuracy and reliability of the system can be improved by using position sensors.
- Common brushless motor position sensors
Several common position sensors for brushless motors include Hall sensors, photoelectric encoders and magnetic sensors. Among them, Hall sensors are widely used in brushless motors because of their simple structure, fast response and low price.
1) Hall sensor
The Hall sensor is a sensor that works based on the Hall effect. The Hall effect refers to the fact that when current passes through a conductor, if the conductor is subjected to a magnetic field perpendicular to the current, a voltage proportional to the strength of the magnetic field will be generated in the conductor. The rotor of a brushless motor is usually equipped with a permanent magnet, and the Hall sensor is installed on the stator to determine the position of the rotor by sensing the change in the rotor magnetic field.
The Hall sensor generally adopts a three-way output method to determine the specific position of the rotor by detecting the combination of the output signals of the three sensors. This method can accurately determine the angular position of the rotor and provide real-time feedback to the control system, thereby controlling the switching and commutation of the current.
2) Photoelectric encoder
The photoelectric encoder works on the principle of optical sensing and is often used in position detection situations that require higher precision. There is a rotating plate on the encoder with a precise optical scale on the plate. When the plate rotates, the sensor generates a digital signal based on the change in light to accurately record the position of the rotor. Compared with Hall sensors, photoelectric encoders provide higher resolution and accuracy, but the cost is also higher.
3) Magnetic sensor
A magnetic sensor is a sensor that uses changes in magnetic field to determine position. It is similar to a Hall sensor, but it is common to use a more efficient magnetoresistance effect or other magnetic technology, and has a strong anti-interference ability.
- Working mechanism of position sensor
Take the Hall sensor as an example. When the motor is running, the permanent magnet fixed on the rotor will generate a constant magnetic field. The Hall sensor determines the position of the rotor by sensing the changes in this magnetic field. The signal output by the Hall sensor will be received by the electronic controller, and the current on-off sequence of the stator winding will be adjusted according to these signals to ensure smooth and efficient operation of the motor.
During the commutation process of the brushless motor, the control system needs to decide which winding to connect based on the rotor position feedback from the sensor. As the rotor rotates, the Hall sensor will detect different magnetic field directions and intensities in turn, output different electrical signals, and the controller will accurately commutate according to these signals.
The position sensor of the brushless motor is a key component for achieving precise control and efficient operation. By monitoring the position of the rotor in real time, the position sensor can provide the control system with necessary feedback information to ensure that the motor operates in the intended manner. Whether it is a Hall sensor, photoelectric encoder or magnetic sensor, they all have their own advantages and disadvantages. Choosing the right sensor type has an important impact on the performance and application of the motor.
If you want to know more about “brushless motor”, you can contact online customer service. X-TEAM brushless motor provides OEM and ODM services for a long time to meet the different needs of different customers.