Electric Machine Position Sensing With Magnetic Field Amplification
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Solution Overview
Problem
Existing synchronous motors using Hall effect sensors for rotor position measurement suffer from measurement uncertainty and alignment errors, leading to motor torque oscillations and suboptimal current control, particularly at high speeds and in compact designs.
Innovation Solution
A single-piece metal component is integrated with the stator to amplify the normal component of the magnetic field near the magnetic sensors, reducing measurement uncertainty and ensuring consistent angular separation between sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Hall effect sensors are used to measure rotor position, then the motor can be controlled in brushless operation, but measurement uncertainty leads to torque oscillations and suboptimal current control
Solution Approach 1:
A ferromagnetic component with specifically designed geometry (protrusions and recesses) is introduced as an intermediary between the rotor magnets and Hall effect sensors. This component modifies the magnetic field distribution to create enhanced gradients at sensor locations, thereby improving measurement precision without compromising brushless operation reliability
Solution Approach 2:
The invention changes the physical parameters of the magnetic field by introducing a ferromagnetic component with specific geometric features. The protrusions and recesses alter the magnetic flux density and its gradient, transforming the field characteristics to improve sensor measurement accuracy while maintaining system reliability
2Measurement precision
If the magnetic field is amplified near the sensors, then measurement accuracy improves, but the magnetic field may saturate the sensor housing
Solution Approach 1:
The ferromagnetic component features localized protrusions and recesses that create concentrated magnetic field gradients only at specific locations near the sensors. This local modification amplifies the field where needed for measurement while preventing saturation in other areas of the sensor housing through the recesses that provide magnetic flux pathways
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 solution enhances the accuracy of rotor position detection, minimizing torque oscillations and improving current control without altering the motor's architecture or adding bulk, thus ensuring precise rotational control.
Implementation Method 1
the part includes a zone configured to amplify the normal component of the magnetic field at the magnetic sensor, in particular a gradient of the normal component of the magnetic field
Implementation Method 2
magnetic sensors, such as Hall effect sensors... These sensors can measure the direction of a normal component of the magnetic field
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to an electric machine comprising a rotor and a stator. The rotor (40, 4) comprises a plurality of permanent magnets (4), the stator comprises a plurality of coils suitable for being powered by an electric current and two Hall effect sensors (6) on supports (60). The sensors are configured to detect a change in gradient of the normal component of a magnetic field generated by the permanent magnets (4). The stator comprises a part (7) comprising - a first zone (7a), - a second zone (7b), and a third zone (7c) extending from the first zone (7a) up to the second zone (7b). The maximum radial thickness of the third zone (7c) is less than the minimum radial thickness of the first zone and the second zone.