Sensorless Electric Machine Rotor Circuit Saliency
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Solution Overview
Problem
Current electric machine technologies face challenges in achieving full torque control without position sensors, leading to increased complexity, cost, and reliability concerns, especially at high-load levels where small signal saliency is lost.
Innovation Solution
The implementation of a rotor circuit made of conductive, non-magnetic material within the electric machine, which introduces magnetic saliency through specific orientation and high-frequency excitation, allowing for sensorless operation by measuring impedance variations and maintaining saliency across loading levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position sensors (encoder, tachometer, or resolver) are used with electric machines, then position information is obtained for torque control, but system cost, complexity, and reliability concerns increase
Solution Approach 1:
The patent extracts the position sensing function from external sensors and relocates it to the rotor structure itself through magnetic saliency. The rotor's geometric asymmetry creates inherent magnetic anisotropy that encodes position information in the magnetic field, eliminating the need for separate position sensors and their associated cabling and interface electronics.
Solution Approach 2:
The rotor structure serves dual purposes: it generates torque through electromagnetic interaction while simultaneously providing position information through its magnetic saliency characteristics. The asymmetric rotor geometry self-encodes position data in the magnetic field distribution, allowing the machine to sense its own position without external sensors.
2Device complexity
If encoderless control with high frequency injection is used, then position sensor complexity is reduced, but full torque capability is lost at high-load levels due to loss of small signal saliency
Solution Approach 1:
The patent deliberately introduces geometric asymmetry in the rotor structure (such as non-circular rotor shapes or asymmetric magnet arrangements) to create strong magnetic saliency. This asymmetry ensures that the magnetic inductance varies significantly with rotor position, maintaining detectable saliency signals even at high load conditions where conventional symmetric rotors fail.
Solution Approach 2:
The patent modifies the rotor's magnetic parameters by changing its geometric configuration to enhance saliency. By altering the rotor's physical shape or magnetic distribution, the patent creates a system where the magnetic inductance ratio (Ld/Lq) is sufficiently large to maintain encoderless control effectiveness across the full torque range, including high-load operating conditions.
3Measurement precision
If position sensors and their cabling are used, then position control is achieved, but a significant portion of motor drive system cost is contributed
Solution Approach 1:
The patent removes the expensive position sensing subsystem (encoders, resolvers, tachometers, cabling, and interface electronics) and replaces it with a passive magnetic saliency-based sensing mechanism inherent to the rotor structure. This extraction eliminates a major cost contributor while maintaining position control capability through magnetic field analysis.
Solution Approach 2:
Instead of using physical position sensors that directly measure rotor angle, the patent creates a magnetic field signature (copy of position information) through the rotor's magnetic saliency. This magnetic signature encodes the rotor position in the same way a sensor would output, but without requiring any additional sensing hardware beyond the rotor's inherent magnetic properties.
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 full torque control and efficient operation without position sensors, maintaining performance, efficiency, and reliability by introducing and sustaining small signal saliency, even at high loads.
Implementation Method 1
a rotor circuit configured to introduce saliency based on an orientation of a portion of the rotor circuit in relationship to a pole location of the electric machine
Implementation Method 2
The implementation of a rotor circuit made of conductive, non-magnetic material within the electric machine, which introduces magnetic saliency through specific orientation and high-frequency excitation, allowing for sensorless operation by measuring impedance variations
Data Source
AI summary
An electric machine that includes a rotor core made of magnetic steel; a stator configured with stationary windings therein; openings disposed within or on the rotor core; and a rotor circuit that is configured to introduce saliency based on an orientation of part of the rotor circuit in relationship to a pole location of the electric machine, where the rotor circuit is made of a conductive, non-magnetic material. A rotor component and various embodiments of electric machines are also disclosed. The present invention has been described in terms of specific embodiment(s), and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.