Stator Shield Ring Layout for High-Speed Rotor Loss Reduction
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Solution Overview
Problem
High-speed electric motors with overlapping winding systems experience undesired harmonics and elevated rotor losses due to small coil winding numbers, which current countermeasures like passive low-pass filters and multilevel inverters fail to adequately address without increasing complexity and space requirements.
Innovation Solution
A stator design with a laminated core and yoke winding featuring an inner and outer winding part, a soft-magnetic shield around the outer winding, and nonmagnetic connecting elements between the stator lamination and shield, increasing leakage inductance and preventing magnetic short-circuits, thus reducing rotor losses without additional current-smoothing measures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If overlapping winding systems are used for high-speed electric motors, then high speed operation is achieved, but undesired harmonics and elevated rotor losses occur due to small coil winding numbers
Solution Approach 1:
A soft-magnetic shield is introduced as an intermediary component between the outer winding part and the stator lamination. This shield increases the leakage inductance of the motor, which acts as a natural low-pass filter to reduce harmonics in the phase current, thereby reducing rotor losses without requiring additional external filters or complex inverter configurations
Solution Approach 2:
The patent modifies the magnetic circuit parameters by introducing the soft-magnetic shield, which changes the leakage inductance parameter of the motor. This parameter change allows the motor to operate at high speeds while maintaining lower rotor losses by filtering harmonics through the modified magnetic circuit rather than through external components
2Loss of energy
If passive low-pass filters based on coils and capacitors are used to reduce rotor losses, then harmonics are reduced, but a comparatively large installation space is required
Solution Approach 1:
The patent merges the function of harmonic filtering directly into the motor's stator structure by incorporating the soft-magnetic shield into the existing magnetic circuit. This eliminates the need for separate external low-pass filters, thereby reducing installation space while maintaining the ability to reduce rotor losses through increased leakage inductance
Solution Approach 2:
The motor structure itself provides the harmonic filtering function through the soft-magnetic shield that increases leakage inductance. The motor serves its own need for current smoothing without requiring external auxiliary measures, thereby eliminating the space requirements for separate filter components
3Loss of energy
If a multilevel inverter is used to countermeasure harmonics, then rotor losses are reduced, but device complexity and space requirements increase
Solution Approach 1:
The patent replaces the complex electronic control approach of multilevel inverters with a passive magnetic solution. The soft-magnetic shield creates a magnetic field configuration that naturally filters harmonics through increased leakage inductance, substituting complex electronic complexity with a simpler magnetic circuit design
4Device complexity
If the stator lamination and shield ring are directly connected, then structural simplicity is maintained, but magnetic short-circuits occur that reduce leakage inductance
Solution Approach 1:
A nonmagnetic connecting element is introduced as an intermediary between the stator lamination and the soft-magnetic shield ring. This intermediary prevents direct magnetic coupling that would create unwanted short-circuits, thereby maintaining the desired leakage inductance and reducing rotor losses while still providing structural connection
Solution Approach 2:
The connecting elements are made of nonmagnetic material specifically at the interface between the stator lamination and shield ring, creating a localized magnetic barrier. This local change in material property prevents magnetic short-circuits at critical locations while maintaining the overall structural integrity and desired magnetic circuit characteristics
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 operation at high speeds with reduced rotor losses and eliminates the need for complex multilevel inverters or additional filters, optimizing inductance and component strength while minimizing space requirements.
Implementation Method 1
a soft-magnetic shield is formed on the entire circumference around the outer winding part
Implementation Method 2
This pairing increases the leakage inductance and, at the same time, additionally prevents the undesired magnetic short-circuit between these two parts
Implementation Method 3
at least one nonmagnetic connecting element contacts the stator lamination. The soft-magnetic shield ring is arranged between the stator lamination and the soft-magnetic shield
Data Source
AI summary
A permanent-excited electric motor/induction machine has a laminated core (1) made of stator laminations (11) and a yoke winding (2). The yoke winding (2) has an inner winding part (21) and an outer winding port 22. The inner winding part 21 is arranged radially inside the stator lamination (11) in at least one winding receptacle (3). The outer winding part (22) is arranged radially outside the stator lamination (11) on an outer surface (4) of the laminated core (1). A soft-magnetic shield (5) is formed on the entire circumference around the outer winding part (22). At least one nonmagnetic connecting element (6), that contacts the stator lamination (11) and the soft-magnetic shield ring (5), is arranged between the stator lamination (11) and the soft-magnetic shield (5).