Brushed DC Machine Insulating Washer for High Voltage Dust Management
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Solution Overview
Problem
Brushed direct current machines face reduced breakdown resistance due to conductive dust generated by brush-commutator friction, especially at high voltage supplies greater than 72 Vdc, which can lead to insulation degradation and failure, and existing solutions like venting or screens are not applicable to sealed machines.
Innovation Solution
The design incorporates a stator with insulating flanges and a washer with blades and ribs to deflect and retain conductive dust, increasing the distance between potentials and lengthening creepage paths, thereby enhancing breakdown resistance without compromising sealing or requiring vents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the supply voltage is increased to achieve higher power output, then the power capability is improved, but the amount of conductive dust generated increases, reducing breakdown resistance
Solution Approach 1:
The patent extracts and removes conductive dust from the machine interior using a suction device with a suction opening positioned near the commutator. The suction device actively removes dust particles before they can deposit on insulating materials, thereby maintaining breakdown resistance while allowing high voltage operation that generates more dust.
Solution Approach 2:
The patent introduces an intermediary airflow system that acts as a mediator between the dust generation source (brush-commutator interface) and the dust collection point. The airflow, generated by a fan or suction device, transports conductive dust particles away from critical insulating components, preventing dust accumulation and maintaining electrical insulation integrity.
2Reliability
If vents are added to expel conductive dust, then the breakdown resistance is improved, but the protection rating deteriorates
Solution Approach 1:
The patent uses a flexible sealing arrangement around the suction opening that allows dust removal functionality while maintaining the sealed enclosure. The sealing element flexes to accommodate the suction device's movement or adjustment while preventing dust and moisture ingress, thus preserving IP54 protection rating while enabling active dust extraction.
Solution Approach 2:
The suction opening and sealing arrangement serve multiple functions: they enable conductive dust extraction to maintain breakdown resistance, while simultaneously maintaining the dust- and splash-proof enclosure for protection rating. This multi-functional design eliminates the need to choose between dust removal and sealing.
3Reliability
If screens are installed to limit dust deposition, then the breakdown resistance is improved, but the device complexity increases
Solution Approach 1:
The patent employs a self-service dust removal system where conductive dust is actively suctioned away from insulating materials and collected in a dust container. This self-contained system continuously maintains breakdown resistance without requiring complex screen structures, achieving dust management through active removal rather than passive filtration.
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 maintains high breakdown resistance even after extended operation, ensuring reliable performance in sealed machines with high voltage supplies while preventing dust infiltration and maintaining IP54 protection.
Implementation Method 1
The blades (114) generate, when the rotor (6) turns, an air current that carries away the conductive dust from the bearing (30)
Implementation Method 2
the friction of the brushes on the commutator generates conductive dust, such as coal dust. More specifically, this conductive dust is typically generated by electrical arcs that occur between the brushes and the commutator during current reversals in the rotor windings
Implementation Method 3
a stator equipped with: permanent magnets or stator windings capable of inducing a magnetic flux, a first and a second end flange comprising, respectively, a first and a second hub, brushes
Data Source
Figure 1~5
AI summary
This brushed DC machine has a protection rating greater than or equal to IP54 and is suitable for being powered by a supply voltage greater than 72 Vdc. This machine is equipped with a wound rotor having a washer (44) of electrically insulating material fixed without any degree of freedom on a shaft (40) of the rotor, this washer: • being interposed between a commutator (42) of the rotor and a first bearing (30), and • having a front face turned towards the commutator (42) and blades (114) projecting from this front face.