BLDC Motor Hall Sensor Layout for Startup Direction Detection
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Solution Overview
Problem
Brushless direct-current electric motors used in motor vehicle equipment face challenges in controlling the rotor's angular position due to the complexity of switching operations, particularly in compact designs where commercially available Hall effect sensors cannot be positioned optimally with small control magnets, limiting their size and cost-effectiveness.
Innovation Solution
A brushless direct-current electric motor design incorporating a rotor with magnetic elements and a control magnet having three times the pole pair number, using two Hall effect sensors positioned on a printed circuit with an angle greater than or equal to 10° between their straight lines through the control magnet's center, where one sensor determines switching instants and the other, in combination, determines the rotor's direction of rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If two Hall effect sensors are positioned closely together for rapid detection of rotation direction, then the detection speed is improved, but the sensors cannot be positioned at the required angle due to their size
Solution Approach 1:
The patent changes the angular parameter between sensors from the conventional 10° to a larger angle (e.g., 30° or more). This parameter change allows the use of larger Hall effect sensors with better performance characteristics while maintaining the ability to detect rotation direction, thereby resolving the contradiction between detection speed and sensor positioning feasibility.
2Volume of moving object
If the overall dimensions of the motor are reduced, then the motor becomes more compact, but the positioning of Hall effect sensors becomes more difficult
Solution Approach 1:
The patent integrates the Hall effect sensors into the stator structure rather than positioning them separately near the rotor. By embedding sensors within the stator's magnetic circuit path, the design achieves compact overall dimensions while providing sufficient space for proper sensor positioning and signal detection, thus resolving the contradiction between compactness and manufacturability.
3Volume of moving object
If a small control magnet is used, then the motor size is reduced, but the angle between sensors and magnet center cannot be achieved
Solution Approach 1:
The patent performs preliminary positioning of the Hall effect sensors within the stator structure during the manufacturing process. By pre-establishing the sensor locations and orientations before final assembly, the design ensures that the required angular relationships are achieved even with a compact control magnet, thereby resolving the contradiction between magnet size and positioning precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for precise control of the motor's operation, enabling smaller overall dimensions and reduced costs while maintaining high running torque without the need for extensive electronic signal processing, effectively addressing the size and positioning limitations of traditional sensor arrangements.
Implementation Method 1
at least a first and a second Hall effect sensor, preferably only a first and a second Hall effect sensor, said Hall effect sensors being configured for detecting predetermined angular positions of the rotor
Data Source
AI summary
A brushless DC motor (1) comprises a rotor comprising magnetic elements twining poles of the electric motor (1) and a control magnet comprising a number of pole pairs equal to three times that of the electric motor (1), a stator having electromagnetic excitation coils, at least one first and one second Hall-effect sensor (17, 17′) configured to detect predetermined angular positions of the rotor, and a control unit configured to apply a predetermined sequence of excitation signals to the coils, wherein the Hall-effect sensors are spaced apart by an angle greater than or equal to 10°, the first Hall-effect sensor (17) is used to determine the switching times of the excitation signals and the second Hall-effect sensor (17′) is used, in combination with the first Hall-effect sensor (17), to determine the direction of rotation of the rotor when the motor starts up, or vice versa.