Single-Hall Brushless Motor Layout for Precise Commutation
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Solution Overview
Problem
Brushless one-phase driving motors with non-symmetric stator back-iron structures face reduced electrical performance due to the need to switch off stator coils during rotor rotation to accurately sense commutation moments, especially when using hall sensors.
Innovation Solution
A brushless one-phase driving motor with a non-symmetric stator back-iron structure and a single hall sensor positioned radially opposite to the stator coil, allowing the coils to remain active during most of the rotation while ensuring precise commutation detection, utilizing a simple analog control device without a microprocessor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hall sensor is used to detect the commutation moment in a brushless one-phase driving motor with non-symmetric stator back-iron structure, then the commutation sensing accuracy is improved, but the electrical performance of the motor is significantly reduced because the stator coil must be switched off twice during every complete rotor rotation
Solution Approach 1:
The patent positions the hall sensor in a different spatial dimension - specifically in the axial direction rather than in the radial plane where the stator coil generates its magnetic field. The sensor is arranged at an axial distance from the stator coil, allowing it to detect the rotor's magnetic field without being overwhelmed by the coil's field, thus eliminating the need to switch off the coil for accurate sensing.
Solution Approach 2:
The patent introduces a magnetic separator (pole separation gap) as an intermediary element between the stator coil and the hall sensor position. This magnetic separator helps to shield or reduce the aerial magnetic field from the stator coil at the sensor location, allowing the hall sensor to detect the rotor's magnetic field accurately even when the stator coil is active.
2Reliability
If the stator coil is switched off for a particular period to enable accurate hall sensor detection, then the commutation moment detection is improved, but the motor performance is significantly reduced
Solution Approach 1:
The patent performs preliminary spatial arrangement of the hall sensor in a position where it can detect the rotor's magnetic field accurately before the stator coil is activated. By pre-positioning the sensor in the axial direction at an appropriate distance, the system ensures reliable commutation detection without needing to interrupt the stator coil operation, thus maintaining continuous motor performance.
3Ease of manufacture
If a non-symmetric stator back-iron structure with a single stator coil in satellite position is used, then the motor construction is simplified and cost is reduced, but the sensing of the correct commutation moment becomes difficult without hall sensors
Solution Approach 1:
The patent utilizes the non-symmetric stator back-iron structure with a single satellite-positioned stator coil, which simplifies the motor construction and reduces costs. This asymmetric design is complemented by positioning the hall sensor in the axial direction, which enables reliable commutation detection despite the simplified asymmetric stator configuration.
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 enhances motor performance by maintaining stator coil activity throughout 360° rotation, ensuring reliable and precise commutation signaling, leading to improved electrical performance and cost-effectiveness.
Implementation Method 1
a motor rotor (30) which is permanently radially magnetized and is rotating around a rotor axis (33)
Implementation Method 2
The driving motor (20) is provided with a non-symmetric stator back-iron structure (40) defining an axial rotor opening (18) defining two stator poles (41, 42)
Implementation Method 3
a single hall sensor being arranged in exactly 180° to the symmetric middle of the two stator coils
Data Source
Figure 1~2
AI summary
The invention is directed to an electrical device (10) comprising a brushless one-phase driving motor (20) and a mechanical unit (12) being driven by the driving motor (20), the driving motor (20) comprising a motor rotor (30) being radially permanently magnetized and rotating around a rotational rotor axis (33), a non-symmetric stator back-iron structure (40) with a rotor opening (18) defining two stator poles (41, 42) and with a lateral bridge portion (43), a single stator coil (50) surrounding the bridge portion (43), a pole separation gap (60) radially opposite to the lateral bridge portion (33) and magnetically separating the stator poles (41, 42), an electronic control device (16) for driving the stator coil (50), and a single hall sensor (52; 56) which is electrically connected to the control device (16), wherein the hall sensor (52; 56) is arranged approximately radially opposite to the stator coil (50) with respect to the rotor axis (33). This arrangement provides a high signal quality for the hall sensor so that a precise commutation is realized.