Expandable Rotor for Electric Machine Field Weakening
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Solution Overview
Problem
Existing electric motors face challenges with high power losses at high speeds due to uncontrolled permanent magnet magnetic fields, and traditional active mechanical field weakening methods are complex and costly.
Innovation Solution
An electric machine with an expandable rotor design, where rotor segments are radially movable and flexibly connected by springs or elastomeric materials, allowing centrifugal forces to increase the radial gap and provide passive magnetic field weakening, with a sleeve to limit expansion and ferrous wedges for continuous conductive connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radial gap is increased to prevent rotor-stator contact, then reliability is improved, but power losses increase and efficiency deteriorates
Solution Approach 1:
The rotor is designed with expandable rotor segments that can dynamically adjust the radial gap size. The rotor segments are spring-loaded to normally engage with the stator for maximum efficiency, and can expand outward under centrifugal force at high speeds to prevent contact and damage, thus dynamically optimizing the radial gap based on operating conditions
Solution Approach 2:
The radial gap parameter is made variable rather than fixed. The rotor segments can change the radial gap dimension from a small value during normal operation to a larger value during high-speed operation, allowing the system to adapt to different operating regimes and optimize both efficiency and reliability under different conditions
2Loss of energy
If active mechanical field weakening mechanisms are added to reduce high-speed losses, then power losses decrease, but device complexity and cost increase
Solution Approach 1:
The rotor segments utilize centrifugal force generated during high-speed operation to automatically expand outward and weaken the magnetic field. This self-actuating mechanism eliminates the need for external control systems, sensors, or actuators, as the physical laws of centrifugal force naturally provide the field weakening effect when needed
Solution Approach 2:
The patent replaces complex mechanical actuation systems with a passive mechanical field weakening approach. Instead of using motors, hydraulics, or electronics to control field weakening, the system uses the inherent centrifugal forces of rotation to achieve the same effect, substituting active mechanical control with passive physical phenomena
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 design effectively reduces high-speed power losses by passively controlling the magnetic field, improving efficiency and reducing the need for complex actuation mechanisms, while maintaining motor performance and reliability.
Implementation Method 1
when the rotor spins centrifugal forces cause the plurality of rotor segments to move radially outward expanding the radial gap between the rotor and the stator
Implementation Method 2
each adjacent pair of the plurality of rotor segments are flexibly connected to one another by a spring
Data Source
AI summary
An electric machine includes a stator and a rotor positioned in operational engagement with one another and defining a radial gap extending circumferentially between the stator and the rotor, the rotor including a plurality of rotor segments defining a plurality of segment gaps between adjacent pairs of the plurality of rotor segments, the rotor segments radially moveable relative to the stator, wherein movement of the plurality of rotor segments radially outward increases the radial gap between the stator and the rotor and the segment gaps between adjacent pairs of the plurality of rotor segments.