Electric Machine with Inner Magnet Hub for Iron Loss Reduction
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Solution Overview
Problem
Electric machines, such as motor/generators in flywheel power storage systems, experience significant iron losses during steady-state operation due to magnetic field variations, leading to inefficiencies and increased costs, especially in large applications where standby time is prolonged.
Innovation Solution
The design incorporates a configuration with a generally annular outer rotor and inner rotor, both equipped with permanent magnets, and a non-magnetically conductive stator winding that generates a magnetic field interacting with the rotor fields, minimizing iron losses by maintaining aligned magnetic field paths and eliminating the need for field coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If field coils are used to provide magnetic field during high loads, then output power can be increased, but iron losses increase during standby mode and system complexity increases
Solution Approach 1:
The patent extracts the magnetic field generation function from the stator field coils and relocates it to permanent magnets mounted on the rotor. This allows the stator to operate without field coils during standby mode, eliminating iron losses in the stator core, while still providing the necessary magnetic field for power generation when the load requires output power.
Solution Approach 2:
The patent implements a dynamic configuration where permanent magnets are mounted on the rotor such that their magnetic fields can be oriented to align with or oppose the stator magnetic field depending on operating conditions. During standby, the rotor magnets are positioned to minimize stator field variations; during power generation, they are positioned to maximize flux linkage and output power.
2Power
If field coils are used to provide magnetic field, then output power can be increased, but device complexity and potential failure points increase
Solution Approach 1:
The patent removes the field coil system entirely from the stator and replaces it with permanent magnets on the rotor. This eliminates the field coil power supply system, reducing the number of components, connection points, and potential failure modes while maintaining the capability to generate the necessary magnetic field for power output.
Solution Approach 2:
The permanent magnets on the rotor serve dual functions: they provide the magnetic field necessary for power generation and simultaneously act as the rotating element that generates electromagnetic induction in the stator windings. This self-service approach eliminates the need for separate field excitation systems.
3Reliability
If permanent magnets are used in rotor, then reliability is improved and field coil trade-offs are eliminated, but iron losses during steady state operation increase
Solution Approach 1:
The patent employs a dynamic arrangement where permanent magnets are mounted on the rotor in a configuration that allows their magnetic fields to align with the rotor's rotational position. During steady-state standby operation, the rotor magnets are positioned such that their fields do not create varying flux in the stator core, minimizing iron losses. When power generation is required, the magnets are positioned to maximize flux linkage with the stator windings.
Solution Approach 2:
The patent changes the operational parameters of the permanent magnets by controlling their angular position on the rotor. By adjusting the orientation and position of the magnets relative to the stator, the system can maintain constant or minimized magnetic field exposure to the stator core during standby, thereby reducing iron losses, while still providing full magnetic field strength when power generation is required.
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 configuration reduces iron losses, enhances operational efficiency, and maintains reliability without the trade-offs of field coil systems, such as lower output efficiency and potential failure points, while allowing for efficient power storage and generation.
Implementation Method 1
A stator winding is arranged to generate, when supplied with electrical power, a magnetic field that interacts with the magnetic fields of the first and second permanent magnets to drive the first and second permanent magnets to rotate about the rotational axis
Implementation Method 2
A stator winding is arranged to generate, when supplied with electrical power, a magnetic field that interacts with the magnetic fields of the first and second permanent magnets
Data Source
AI summary
An electric machine includes a generally annular outer rotor supported to rotate about a rotational axis. The outer rotor defines an internal cavity therein and has a plurality of permanent magnets in the internal cavity generating a first magnetic field. An inner rotor is in the internal cavity and is supported to rotate about the rotational axis. The inner rotor has a plurality of permanent magnets about its perimeter that generate a second magnetic field. A generally annular stator is in the internal cavity between the outer rotor and the inner rotor. The stator has a stator winding supported by a non-magnetically conductive stator core. The stator winding is arranged to generate a field that interacts with the first and second magnetic fields. One of the outer rotor or the inner rotor is mechanically coupled to drive a load. The other of the outer rotor or the inner rotor is not mechanically coupled to drive the load.