Hall sensor in brushless DC motor: working principle and application
1. Working Principle of Hall Sensors :
- Hall sensors operate based on the Hall effect, capable of detecting the presence, direction, and strength of magnetic fields.
- In BLDC motors, three Hall sensors are arranged at 120-degree intervals to monitor the rotor's position, assisting the controller in determining when to change the current direction.
2. Functions of Hall Signals :
- Indicate the position of the rotor's magnetic poles to help the controller precisely control the motor.
- Mark the commutation points, i.e., the moments when the current direction needs to be changed.
- Provide speed information by measuring the frequency of the Hall sensor signals.
3. Signal Output Example :
- Three Hall sensors (H1, H2, H3) output six different states as the motor runs for six cycles, providing continuous position feedback to the motor controller.
4. Types of Hall Sensors :
- Linear Hall sensors: Output a continuous voltage signal proportional to the detected magnetic field strength.
- Digital Hall sensors: Output a high level (or low level) when the magnetic field reaches a preset threshold, and a low level (or high level) when the magnetic field is below another threshold.
5. Advantages of Hall Sensors :
- Provide accurate rotor position detection, simplify control algorithms, and improve the reliability of start-up and low-speed control.
- Compared to motors without Hall sensors, although the cost and complexity increase, they offer more direct position feedback.
The article emphasizes the importance of Hall sensors in improving the performance of BLDC motors, including aspects such as position sensing, start-up and low-speed control, control simplicity, and the trade-off between cost and complexity.
