Rectified Rotor Windings for Low-Torque-Ripple Synchronous Motors
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Solution Overview
Problem
Existing electric motors face challenges in reducing torque ripple and efficiency, particularly in synchronous machines, due to reliance on rare-earth magnets and separate brush or exciter circuits, which increase costs and complexity.
Innovation Solution
The implementation of a field wound synchronous motor with a rectifier in the rotor coils, which includes a diode, allows for efficient operation by adjusting current magnitude and angle in response to operating conditions, reducing torque ripple and eliminating the need for rare-earth magnets and separate excitation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rare-earth magnets and separate brush or exciter circuits are used in synchronous machines, then motor performance can be maintained, but costs and device complexity increase
Solution Approach 1:
The patent extracts and eliminates the separate exciter circuit and brush components from the motor design. Instead of using a separate exciter circuit to provide rotor windings, the invention uses the stator windings directly to generate the rotating magnetic field that energizes the rotor, thereby removing unnecessary components and simplifying the overall device structure while maintaining motor performance
Solution Approach 2:
The stator windings serve multiple functions: they generate the rotating magnetic field that drives the rotor and simultaneously provide the excitation current for the rotor windings without requiring a separate exciter circuit. This multi-functionality reduces device complexity while maintaining the required motor performance
2Reliability
If rare-earth magnets and separate brush or exciter circuits are used in synchronous machines, then motor performance can be maintained, but costs increase
Solution Approach 1:
The invention removes the separate exciter circuit and brush components, eliminating the need for rare-earth magnets in the exciter assembly. This reduction in component count and material requirements directly lowers manufacturing costs while maintaining motor performance through the simplified direct-stator-excitation architecture
Solution Approach 2:
The patent replaces expensive rare-earth magnets with conventional materials in the rotor windings that are energized by the stator-generated magnetic field. The use of standard copper windings and elimination of precious metal dependencies reduces material costs and simplifies manufacturing processes
3Loss of energy
If rectifier is added to rotor coils, then torque ripple is reduced and efficiency is enhanced, but device complexity increases
Solution Approach 1:
The rectifier is integrated directly into the rotor coil assembly, merging the rectification function with the existing rotor structure. This integration approach minimizes additional complexity by using the same magnetic circuit and structural framework already present in the motor, rather than adding separate rectification systems
Solution Approach 2:
The rectifier in the rotor coils automatically converts the induced alternating current into direct current, enabling the rotor windings to maintain a unidirectional magnetic field that reduces torque ripple. This self-regulating rectification process occurs without external control systems, improving efficiency while adding minimal complexity to the overall device
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 solution enhances motor efficiency, reduces torque ripple, and lowers operational costs by maintaining synchronicity between the stator and rotor magnetic fields, while also providing effective transient damping across a wide range of frequencies.
Implementation Method 1
A rotor defines multiple fixed rotor poles with associated rotor windings that include a rectifier and are configured to be energized only by the stator. The rotor defines a rotor field energizable by magnetic fields produced by the stator windings to produce relative motion between the rotor and the stator.
Implementation Method 2
A rotor defines multiple fixed rotor poles with associated rotor windings that include a rectifier. The rotor windings include a rectifier. A delay of energization of flux in an air gap is reduced by a rectifier.
Implementation Method 3
A controller is configured to send a current through the stator windings at a current angle measured relative to a closest one of the rotor poles. The controller is configured to adjust the current angle in response to operating conditions. The rotor is maintained in synchronicity with the magnetic fields produced by the stator windings during operation.
Implementation Method 4
A force tangential to the rotor is generated by a shift in the stator magnetic field. The rotor is moved by the generated tangential force.
Data Source
AI summary
An electric machine includes a stator defining multiple stator poles with associated stator windings configured to receive a stator current. The electric machine also includes a rotor defining multiple fixed rotor poles with associated rotor windings, wherein the rotor defines a field energizable by magnetic fields produced by the stator windings when receiving the stator current to produce relative motion between the rotor and the stator and wherein the rotor is maintained in synchronicity with the magnetic fields produced by the stator during operation of the electric machine. The electric machine also includes a rectification system configured control against an alternating current being induced in the rotor poles as the field is energized by magnetic fields produced by the stator windings when receiving the stator current.