Brush-Commutated DC Motor Coil Layout for Reduced Commutation Oscillation
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Solution Overview
Problem
Brush-commutated DC electric motors experience oscillations and current modulations at the collector, leading to radial deflection of the rotor due to the blocking and re-establishment of sub-coil currents during commutation, which cannot be completely prevented by existing solutions.
Innovation Solution
The arrangement of sub-coils is optimized such that multiple sub-coils, offset by 360°/n rotationally symmetrically, are supplied with the same current, either in series or parallel, and connected in a uniform design to prevent oscillations, with graphite brushes and a self-supporting iron-free winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If sub-coils are energized during commutation in conventional brush-commutated DC motors, then the motor produces torque and rotates, but oscillations and current modulations occur at the collector leading to radial deflection of the rotor
Solution Approach 1:
The rotor winding is divided into multiple independent sub-coils (at least two) that are spatially segmented around the rotor periphery. Each sub-coil can be independently controlled and energized at different times, allowing the motor to maintain continuous torque production while reducing oscillations by distributing the electromagnetic forces across multiple segments rather than having them concentrated in a single coil.
Solution Approach 2:
The control system implements periodic energizing of sub-coils in a specific sequence that synchronizes with the rotor rotation. By periodically activating different sub-coil pairs and controlling their current waveforms, the system maintains continuous torque while the periodic nature of the control helps to regularize and reduce oscillatory effects at the collector.
2Speed
If the current of a sub-coil is blocked and re-established during commutation, then the motor continues rotation, but this causes oscillations that deflect the rotor radially at the collector
Solution Approach 1:
The control system performs preliminary action by pre-charging capacitor banks before commutation events. These capacitors store energy and are connected to sub-coils just before they need to be energized, ensuring smooth current establishment without abrupt blocking and re-establishment. This preliminary preparation reduces the shock and oscillation effects during commutation.
Solution Approach 2:
Capacitor banks are introduced as intermediary energy storage elements between the power supply and the sub-coils. These capacitors act as buffers that smooth out current transitions during commutation, preventing direct blocking and re-establishment of current. The capacitors intermediate the energy transfer, reducing the harmful radial deflection effects while maintaining continuous rotation.
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 significantly reduces oscillations and current modulations, enhancing the motor's operational stability and efficiency by ensuring uniform current distribution across sub-coils, thereby minimizing radial deflection and noise.
Implementation Method 1
a stator which comprises a permanent magnet with a number p of pole pairs, and a rotor which can rotate in relation to the stator, which has a hollow-cylindrical iron-free winding with a geometric axis and a number Q of sub-coils
Data Source
AI summary
The DC electric motor has a stator which comprises a permanent magnet with a number p of pole pairs, and has a rotor which can rotate in relation to the stator and has a hollow-cylindrical iron-free winding with a geometric axis and a number Q of sub-coils, and a collector with a number K of collector segments, wherein the sub-coils are arranged distributed over the periphery of the rotor. The brush-commutated DC electric motor furthermore has at least one pair of brushes which are in contact with the collector and by means of which the sub-coils are energized. The arrangement of the brushes and the interconnection of the sub-coils are selected in such a way that in each case a number n≥2 of sub-coils, which are each arranged offset by 360°/n in a rotationally symmetrical manner with respect to the axis of the rotor, are always supplied with the same current at the same time.