Sensorless Rotor Position Detection Using Induced Voltage Relationships
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Solution Overview
Problem
Conventional three-phase motor detection methods without sensors fail to accurately detect rotor position at standstill, leading to decreased starting torque and potential motor abnormalities, which is critical in applications like hard drives where normal operation and prevention of motor burnout are essential.
Innovation Solution
A detection device and method using a full-bridge circuit, logic circuit, selector, and processor to sequentially output six different voltage vectors to the stator winding coils, generating induced voltages, and referencing a rotor position table to determine the rotor position based on calculated voltage relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensor-based detection method is used, then rotor position can be detected, but the overall size and cost of the motor increases and system stability decreases
Solution Approach 1:
The patent extracts the detection function from external sensors and implements it within the existing motor control system using the full-bridge circuit and logic circuit. By removing the hall sensor and using the motor's own winding inductance characteristics for position detection, the system achieves sensorless detection that maintains stability while reducing size and cost.
Solution Approach 2:
The motor system uses its own electrical characteristics (winding inductance changes with rotor position) to perform self-detection of rotor position. The full-bridge circuit sequentially inducts different coils and the logic circuit detects voltage differences, allowing the motor to detect its own position without external sensors, thereby improving reliability.
2Device complexity
If sensorless detection method is used, then device complexity is reduced, but rotor position cannot be accurately detected in standstill state
Solution Approach 1:
The patent applies preliminary action by sequentially inducting different coils through the full-bridge circuit before actual motor operation. The logic circuit pre-detects voltage differences across coils in different sequences, allowing accurate rotor position determination even in standstill state. This preliminary detection sequence enables precise position measurement without requiring motor rotation.
Solution Approach 2:
The system dynamically switches the inductance sequence of different coils through the full-bridge circuit and logic circuit. By changing which coils are inducted and in what sequence, the system can detect rotor position accurately across different operational states including standstill, maintaining measurement precision while keeping the device simple.
3Device complexity
If conventional detection method is used, then device complexity is reduced, but starting torque decreases and motor may operate abnormally
Solution Approach 1:
The logic circuit performs preliminary detection of rotor position by sequentially inducting coils through the full-bridge circuit before motor start-up. This preliminary action accurately determines the initial rotor position, enabling proper commutation timing and ensuring adequate starting torque while preventing abnormal motor operation.
Solution Approach 2:
The system implements feedback by continuously monitoring voltage differences detected by the logic circuit and using this information to control the full-bridge circuit's commutation timing. This feedback mechanism ensures accurate rotor position information is available for optimal starting torque and prevents abnormal operation, all while maintaining simple device architecture.
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
Enables accurate detection of rotor position in a standstill state, preventing abnormal operation and motor burnout by measuring induced voltages under different voltage vectors and correlating them with predefined voltage relationships in a rotor position table.
Implementation Method 1
The logic circuit is configured for sequentially outputting six different voltage vectors to the full-bridge circuit to control the full-bridge circuit sequentially inducting two of the three coils
Implementation Method 2
When the induced magnetic field direction is opposite to the magnetic field direction of the rotor 20, the magnetic saturation effect will be weakened, so that the inductance of the stator winding 10 increases
Data Source
AI summary
A detection device and a detection method of a rotor position of three-phase motor are disclosed which measure induced voltages under different voltage vectors and calculate an induced voltage relationship among the different induced voltages. Then the detection device and the detection method find out the rotor position suitable for the induced voltage relationship according to a rotor position table. Therefore, the detection device and the detection method can accurately detect the rotor position in a standstill state to prevent the three-phase motor from operating abnormally and burning out.