External Rotor Synchronous Machine Centrifugal Stability
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Solution Overview
Problem
Current electrical synchronous machines, particularly internal rotor machines, face limitations in achieving high circumferential speeds due to centrifugal forces, which compromise mechanical stability and increase manufacturing complexity, and have a suboptimal magnetic field strength-to-structural volume ratio.
Innovation Solution
The development of an external rotor synchronous machine with a rotor yoke and independently configured rotor poles, using a form-fitted connection and polygonal conductor cross-section rotor coils, allows for higher circumferential speeds and reduced manufacturing complexity by compressing the rotor winding against a more stable rotor yoke, enhancing magnetic field strength and operational security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal rotor machine configuration is used, then mechanical stability is compromised under high centrifugal forces, but external rotor configuration increases rotor radius and winding complexity
Solution Approach 1:
The patent inverts the conventional internal rotor configuration by adopting an external rotor design where the rotor winding is arranged on the outer circumference rather than inside the rotor. This inversion allows the rotor yoke to provide superior mechanical stability against centrifugal forces while the rotor poles extend radially outward to carry the windings, resolving the contradiction between mechanical stability and winding accessibility.
Solution Approach 2:
The rotor is segmented into distinct components: a rotor yoke providing structural stability, and multiple independent rotor poles extending radially outward. Each rotor pole can be independently manufactured and assembled, simplifying the overall winding process while maintaining mechanical integrity under high-speed operation.
2Reliability
If pole shoes are dimensioned to retain rotor winding under centrifugal forces, then residual interspaces between rotor poles become small, but this increases manufacturing time and costs
Solution Approach 1:
The rotor poles are pre-assembled with rotor coils in a controlled environment before installation into the final rotor assembly. This preliminary action allows for easier and faster winding operations without the constraint of narrow interspaces, as the poles can be manufactured and prepared independently with adequate access for winding machinery.
3Manufacturing precision
If rotor winding is introduced with great care to prevent damage, then manufacturing precision is improved, but productivity decreases due to long winding time
Solution Approach 1:
By segmenting the rotor into separate poles that can be independently prepared and assembled, the winding process can be performed on each pole separately with adequate space and access. This segmentation enables parallel processing and reduces the overall manufacturing time while maintaining high precision through controlled, individual winding operations.
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 enables higher circumferential speeds while ensuring mechanical stability and simplifying the manufacturing process, achieving a superior magnetic field strength-to-structural volume ratio and reducing the risk of rotor winding dislodgment.
Implementation Method 1
a rotor (64) which rotates about the stator (62) and has a rotor winding (76) which is designed for forming a rotor magnetic field; a stator winding (68) of at least three-phase construction for forming a rotating stator magnetic field
Implementation Method 2
large centrifugal forces act on the rotor, associated with the high motor speeds which are intermittently to be achieved by the electrical machine. In order to counteract this movement or tendential movement, structural measures are implemented
Data Source
AI summary
An electrical synchronous machine is provided for a rail-free vehicle. The vehicle has drive wheels and the synchronous machine is designed to generate a torque, which propels the vehicle, at the drive wheels. The synchronous machine has a stator and a rotor which rotates around the stator, wherein the stator has a stator winding of at least three-phase construction for forming a rotating stator magnetic field, and wherein the rotor has at least one rotor winding which is designed for forming a rotor magnetic field. A method for at least partially circumferentially establishing a current-excited synchronous machine provides a rotor yoke, provides a large number of rotor poles, fastens the rotor poles to the rotor yoke for forming a rotor, provides a stator, and inserts the stator into the rotor.