Asymmetric Rotor Bar Layout for Sensorless Position Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrical asynchronous machines require additional rotor position sensors, increasing complexity and effort for learning processes, and lack efficient methods for determining the rotational position without additional components.
Innovation Solution
The rotor design incorporates at least three different rotor bars with varying widths, creating an asymmetric inductive property that allows for precise determination of the rotational position using the method, eliminating the need for additional sensors and signal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotor position sensor is arranged on the rotor to determine rotational position, then the rotational position can be detected, but the device complexity increases and learning process effort is required
Solution Approach 1:
The patent extracts the rotational position detection function from a separate sensor component and integrates it into the rotor structure itself through asymmetric rotor bars. The asymmetric inductive properties of the rotor bars generate position-dependent impedance variations that can be measured without additional sensors, thereby eliminating the need for rotor position sensors and their signal lines while maintaining detection capability
Solution Approach 2:
The rotor bars serve multiple functions: they provide the essential inductive function for asynchronous machine operation and simultaneously encode rotational position information through their asymmetric arrangement. This multi-functionality eliminates the need for dedicated position sensing components, reducing device complexity while maintaining both motor function and position detection capability
2Measurement precision
If additional rotor position sensors and signal lines are added, then rotational position can be determined, but the electromagnetic compatibility is degraded
Solution Approach 1:
The patent removes the vulnerable signal lines that connect rotor position sensors to the control system. Instead, position information is extracted through impedance measurements of the rotor bars themselves, which are already part of the motor's electrical circuit. This eliminates the need for additional signal transmission paths that would be susceptible to electromagnetic interference
Solution Approach 2:
The patent merges the position detection function with the existing rotor bar structure and its electrical connections. The same rotor bars that carry current for motor operation also provide the position encoding function through their asymmetric inductive properties. This integration eliminates separate signal lines and reduces electromagnetic vulnerability by using existing robust electrical 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 design enables precise and sensorless determination of the rotor's rotational position, reducing component count and improving electromagnetic compatibility, while allowing continuous monitoring during operation.
Implementation Method 1
In electrical asynchronous machines, alternating current is applied to windings in a stator, which generates a magnetic field, which in turn induces a voltage in the rotor. The current flow through the short-circuit ring in the rotor in turn generates a magnetic field
Implementation Method 2
DE 694 32 226 T2 describes a method and a device for the sensorless determination of the position and speed of a rotor of an AC motor. In the method, the rotational position of the rotor relative to the stator is determined by measuring the impedance of the rotor during operation
Data Source
AI summary
A rotor of an electrical asynchronous machine is provided, the rotor comprising a rotor shaft which extends along an axis of rotation, a rotor laminated core which is directly or indirectly connected to the rotor shaft, a plurality of rotor bars which extend in the direction of the axis of rotation and are distributed in the circumferential direction about the axis of rotation, and at least one short-circuit ring which connects all rotor bars to one another in an electrically conductive manner. The plurality of rotor bars comprises at least three different rotor bars, which differ from one another in terms of their width in each case. An electrical asynchronous machine having a rotor, and a method for determining the rotational position of the rotor are also provided.