Brush Arrangement for Electric Motor Commutation
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Solution Overview
Problem
Conventional electric motors with wave windings and fewer brushes than poles experience high power losses, voltage fluctuations, and electromagnetic interference due to non-uniform commutation times.
Innovation Solution
The brushes are arranged with specific circumferential angles to ensure uniform commutation times, reducing current ripple by optimizing their distribution relative to the laminate pitch, with tolerance angles less than 8°, particularly less than 4° or 2°, to minimize power losses and electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wave winding is used with fewer brushes than poles, then device complexity is reduced, but power losses increase and voltage fluctuations occur
Solution Approach 1:
The invention changes the angular position parameter of brushes relative to commutator laminates. By setting the angle between adjacent brushes to differ from the angle between adjacent commutator laminates by a specific amount (within tolerance angle αT < 8°), the commutation times are distributed more uniformly, reducing current ripple and power losses while maintaining the reduced brush configuration
Solution Approach 2:
The invention pre-calculates and sets optimal brush positions during design using the formula involving tolerance angle αT. This preliminary positioning ensures that commutation events are distributed uniformly across the operating cycle, preventing power losses and voltage fluctuations before they occur during motor operation
2Device complexity
If wave winding is used with fewer brushes than poles, then device complexity is reduced, but voltage fluctuations occur
Solution Approach 1:
By modifying the angular parameter of brush positions relative to commutator laminates, the invention achieves more uniform commutation timing. This parameter adjustment smooths current delivery to the armature, stabilizing the voltage output and reducing fluctuations in the vehicle power supply system
Solution Approach 2:
The invention establishes a design feedback relationship where the brush angle is calculated based on the number of poles, commutator laminates, and desired tolerance level. This systematic approach ensures voltage stability is built into the motor's fundamental design rather than added as a separate control system
3Device complexity
If wave winding is used with fewer brushes than poles, then device complexity is reduced, but electromagnetic interference increases
Solution Approach 1:
The invention changes the spatial parameter of brush positioning to achieve uniform commutation distribution. This uniformity reduces abrupt current changes during commutation, thereby minimizing electromagnetic interference and EMC problems while maintaining the simpler wave winding configuration with fewer brushes
4Ease of manufacture
If brushes are positioned at conventional angles, then ease of manufacture is improved, but current ripple increases
Solution Approach 1:
The invention introduces a small angular deviation (tolerance angle αT < 8°) from conventional equidistant brush positioning. This parameter change creates non-uniform angular spacing that compensates for the wave winding's inherent commutation issues, reducing current ripple while remaining manufacturable with standard tolerances
Data Source
AI summary
An electrical machine, in particular an electric motor, has a first number (k) of commutator laminates (10, 12, 14) and brushes (16, 18), wherein the commutator laminates (10, 12, 14) are arranged distributed uniformly in the circumferential direction of a circumference of a laminate support (24). The brushes (16, 18) are arranged such that commutation times are distributed as uniformly as possible in order to reduce current ripple when using a wave winding and a number of brushes (16, 18) which is less than a number of poles (2p) in the electrical machine.