Compensating Load Factors in Permanent Magnet Motors
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Solution Overview
Problem
Permanently excited motors face challenges in accurately determining rotor position based on inductivity, particularly due to load factors, which cause ambiguity and faulty angle determination, especially when using sensor-less methods that rely on inductivity variations.
Innovation Solution
A method and device that measure phase currents or intermediate circuit current to determine corrective values, linking them with inductivity-based signals to stabilize rotor position determination, using a correction device connected to a control unit to adjust switch states for the converter, thereby correcting current-dependent errors and stabilizing inductivity-based signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor-less control methods based on inductivity variations are used to determine rotor position, then system costs and mounting space are reduced, but measurement precision and reliability deteriorate due to load factor interference and ambiguous angle determination
Solution Approach 1:
The patent implements feedback by measuring phase currents or intermediate circuit current, comparing them with expected values, and generating corrective values that are fed back to correct the inductivity-based position signals. This closed-loop approach compensates for load factor disturbances and improves measurement precision without adding sensors.
Solution Approach 2:
The patent changes the parameter being measured from raw inductivity signals to corrected position signals by introducing corrective values derived from current measurements. This parameter transformation eliminates the ambiguity and load factor dependence inherent in direct inductivity-based position determination.
2Device complexity
If inductivity-based signals are used for rotor position determination, then device complexity is reduced, but stability deteriorates due to current-dependent errors and load factor variations
Solution Approach 1:
The correction device continuously monitors current-dependent errors and applies corrective values to stabilize the position signals. This feedback mechanism compensates for load factor variations and maintains signal stability throughout the operating range.
Solution Approach 2:
The patent replaces direct mechanical position sensing with an electrical field-based inductivity measurement system, then stabilizes it through signal processing. This substitution achieves simpler hardware while maintaining stability through computational correction.
3Measurement precision
If corrective values are applied to inductivity-based signals to improve position precision, then measurement precision improves, but device complexity increases due to additional correction device and current measurement requirements
Solution Approach 1:
The correction device performs multiple functions: it measures current, calculates corrective values, and applies corrections to position signals. By consolidating these functions in a single control unit, the patent avoids the need for separate sensors and additional hardware complexity.
Solution Approach 2:
The control system uses its own current measurements to generate corrective values for its own position determination. This self-service approach eliminates the need for external correction devices or additional sensing hardware, maintaining simplicity while improving 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 approach enhances the precision of rotor position detection, prevents faulty position jumps, and improves motor control efficiency by compensating for load factors, making the system more robust and reducing signal strength issues.
Implementation Method 1
either the phase currents are measured or the intermediate circuit current is detected
Implementation Method 2
The saturation of the stator inductivity is affected by the rotor field of the permanent magnets and the current-caused stator field
Implementation Method 3
by means of a control unit switch states, subjected to the corrective value and thus corrected, are supplied to a converter for controlling the motor
Data Source
AI summary
The invention relates methods and devices for compensating for load factors in permanently excited motors, wherein the rotor position is determined from the inductivities of the phases. The methods and devices are characterized by a stabilization of the inductivity-based signals for the determination of the position of the rotor in permanently excited motors against load factors. To this end, advantageously current-dependent faults of the angular values determined during the operation of the motor are corrected. For this purpose, in order to correct the inductivity-based determination of the position of the rotor, in a measuring device either the phase currents are measured or the intermediate circuit current is captured. Furthermore, including at least one motor-specific characteristic value, at least one current-dependent correction value, which is determined from said characteristic value, is applied in a correction device against the inductivity-based signals, which result from the inductivity-based determination of the position of the rotor, of a device for determining the inductivities such that switch states, which are loaded with the correction value by a control device and thus are corrected, are present at a converter for actuating the motor.