Rotor Position Verification in Synchronous Machines
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Solution Overview
Problem
Existing methods for determining the rotor position in electronically-commutated synchronous machines, especially at rest or low speeds, fail to reliably detect sensor malfunctions, leading to potential damage to the motor or driven device due to inconsistencies between actual and sensed rotor positions.
Innovation Solution
A method that determines the relative position of the rotor to stator-mounted sensors by rotating the rotor through a predefined angle and comparing subsequent position determinations with anticipated positions, using commutation schemes to correct for errors and ensure accurate rotor position detection, while limiting currents based on temperature to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotor position is determined using sensors at rest or low speeds, then rotor position can be detected, but sensor malfunctions cannot be reliably detected leading to potential damage
Solution Approach 1:
The patent applies preliminary action by performing rotor position verification before normal motor operation begins. The method rotates the rotor through a predefined angle using voltage vectors and checks if the measured position matches the anticipated position. This preliminary verification detects sensor malfunctions before they can cause damage during actual motor operation, resolving the contradiction between achieving position detection and ensuring reliable malfunction detection.
2Measurement precision
If current vectors are applied to rotate the rotor for position verification, then sensor accuracy can be checked, but excessive current may damage the motor
Solution Approach 1:
The patent applies partial action by using only the minimum necessary current vectors required to rotate the rotor through a predefined verification angle, rather than applying full operating current. This allows sufficient rotor movement for position verification while avoiding excessive current that could cause motor damage. The method uses targeted voltage vectors applied for limited durations solely for the purpose of position checking.
3Reliability
If multiple position determination processes are performed, then sensor deviations can be detected, but the control process becomes more complex
Solution Approach 1:
The patent applies periodic action by performing position determination processes at regular intervals during the verification procedure. The rotor is rotated through predefined angles with repeated position measurements at each step, allowing systematic detection of sensor deviations. This periodic measurement approach provides reliable deviation detection through consistent comparison of measured versus anticipated positions without requiring overly complex continuous monitoring.
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 method enables reliable detection of rotor position sensor deviations, allowing for angular corrections and maintaining high mechanical torque delivery, thereby minimizing risk of damage to the motor or driven device by ensuring accurate rotor position determination and sensor operation.
Implementation Method 1
three Hall-effect sensors fixed to the stator are used for the scanning of a rotary encoder associated with the rotor, or for the direct scanning of the stray field of the rotor magnets
Implementation Method 2
The influx of current to typically three stator windings generates a magnetic field, in which the permanently-excited rotor in arranged. By the appropriate switchover (commutation) of the currents flowing in the stator windings (or of voltages applied), a rotary motion is generated
Data Source
AI summary
An electronically-commutated synchronous system and method includes a permanently-excited rotor and a stator which is provided with three phase windings, together with three rotor position sensors in an appropriate arrangement for a first commutation scheme. The rotor position is determined by the read-out of data from the position sensors. The appropriate voltage vector is defined by a second commutation scheme, and the second rotor position thus determined is compared with the first commutation scheme. If the rotor position sensors are operating correctly, the position of the rotor may be determined to an accuracy which is equivalent to the interval between two columns in the commutation table.