Eddy Current Sensor for Magnetic Bearing Position Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic bearing devices face challenges in reliably controlling the position of rotors, especially under difficult conditions such as large air gaps and the presence of metallic media, due to low signal-to-noise ratios and interference from strong alternating magnetic fields.
Innovation Solution
A magnetic bearing device with a stator winding for generating a magnetic control field and an eddy current sensor system comprising inductance and capacitance in series, forming an electrical oscillating circuit, which enhances the signal-to-noise ratio and allows for precise position control, even through metal walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-contact distance sensors are used to determine rotor position, then the rotor position can be measured without mechanical contact, but the signal-to-noise ratio becomes extremely low in the presence of strong alternating magnetic fields and large air gaps
Solution Approach 1:
The patent introduces a metal wall as an intermediary between the rotor and stator. This metal wall serves as a mediator that the sensor signals must pass through, creating a new measurement path that is less susceptible to electromagnetic interference while still enabling position detection
Solution Approach 2:
The patent replaces traditional inductive sensors with eddy current sensors that operate on different physical principles. The eddy current sensor system uses electromagnetic induction in a different configuration, measuring changes in eddy current patterns rather than direct inductance changes, which provides better immunity to the alternating magnetic fields generated by the drive winding
2Adaptability or versatility
If the air gap between rotor and stator is increased, then the device can accommodate larger components and better cooling, but the sensor signal strength decreases due to the 1/d dependence of inductance
Solution Approach 1:
The patent replaces traditional inductive sensing with eddy current sensing that has different signal decay characteristics. The eddy current sensor measures the perturbation of eddy current patterns in the metal wall caused by rotor position changes, which maintains signal strength better over larger distances compared to direct inductance measurement
Solution Approach 2:
The metal wall acts as an intermediary that extends the effective sensing range. The eddy currents induced in the metal wall create a distributed sensing field that maintains measurement capability over larger air gaps, effectively decoupling the sensor signal strength from direct inverse distance dependence
3Adaptability or versatility
If a metal wall is introduced between rotor and stator, then the device can be used in bioreactors and mixers with metal containment, but traditional non-contact distance measurement becomes extremely difficult or impossible
Solution Approach 1:
The patent transforms the metal wall from an obstacle into the primary sensing medium. The eddy current sensor measures changes in eddy current distribution within the metal wall itself, using the metal wall as an intermediary that carries the measurement information rather than blocking it
Solution Approach 2:
The patent converts the electromagnetic shielding effect of the metal wall, which normally blocks sensor signals, into a beneficial sensing mechanism. The metal wall's electrical conductivity, which causes shielding, is instead exploited to generate eddy currents that respond to rotor position changes, turning the harmful shielding effect into a useful measurement signal
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
The solution significantly improves the precision and stability of rotor position control, enabling reliable operation in challenging environments with large air gaps and metal obstructions, and increases the signal range by a factor of 10 to 50, facilitating applications not previously possible with existing sensors.
Implementation Method 1
a stator (2) that includes a winding (22) for generating a magnetic control field
Implementation Method 2
a sensor device (5) designed as an eddy current sensor for determining the distance between the stator (2) and the rotor (3)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The apparatus (1) has a sensor device provided as an eddy current sensor for determining a spacing between a stator (2) e.g. bearing stator, and a rotor (3) e.g. ring-shaped stator. The sensor device has four sensor elements (51) i.e. air core coils, provided as an inductor and a capacitor that forms an electrical resonant circuit with the inductor. A monitoring unit (6) controls the sensor device and evaluates a set of detected signals. The inductor is electrically arranged in series to the capacitor, so that the electrical resonant circuit is an electrical serial resonant circuit.