Brushless DC Motor Grounding Path for Emission Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless DC motors emit radiated emissions that can interfere with other electronic devices, such as key fobs, and existing methods like shielding are not sufficient to meet legal requirements.
Innovation Solution
A brushless DC motor design that includes a stator formed of stacked laminations with radially extending core members and a circumferential wall, featuring a grounding member that creates a path between the stator and printed circuit board to dissipate high-frequency energy and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If shielding with conductive material or conductive enclosure is used, then electric field emissions are reduced, but device complexity and cost increase
Solution Approach 1:
The invention extracts the harmful high-frequency energy from the motor system by providing a dedicated grounding path that channels this energy away from the motor housing and surrounding environment. The grounding member connected to the iron core at flux null locations extracts the problematic emissions without requiring external shielding structures.
Solution Approach 2:
The grounding member acts as an intermediary element between the iron core and the printed circuit board ground. This mediator provides a controlled path for high-frequency energy dissipation, converting harmful radiated emissions into manageable electrical current that can be safely directed to ground, avoiding the need for complex conductive enclosures.
2Object-generated harmful factors
If grounding path is created through openings in stator and PCB, then radiated and conducted emissions are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention applies local quality by specifically targeting flux null locations on the iron core for grounding connection. These specific locations have unique magnetic properties (minimal flux density) that make them ideal for grounding, and the openings are precisely positioned at these localized areas rather than requiring uniform precision throughout the entire motor structure.
Solution Approach 2:
The grounding member is designed with a specific geometry that facilitates preliminary alignment during assembly. The first section received in the first opening and the second section received in the second opening are configured to guide proper positioning before final securing, reducing the actual manufacturing precision required during the assembly process.
3Object-generated harmful factors
If grounding member connects iron core to ground, then high-frequency energy is dissipated as heat, but energy loss increases
Solution Approach 1:
The invention converts the harmful high-frequency radiated energy into beneficial thermal energy through controlled dissipation. By grounding the iron core at flux null locations, the high-frequency energy that would otherwise be radiated as electromagnetic interference is instead directed through the grounding member and dissipated as heat, transforming a harmful emission into a harmless (and even useful for thermal management) form of energy.
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
The grounding of the motor's iron core significantly lowers both radiated and conducted emissions, meeting legal standards by dissipating energy as heat and detuning the motor to prevent re-radiation.
Implementation Method 1
The grounding of the motor's iron core significantly lowers both radiated and conducted emissions, meeting legal standards by dissipating energy as heat
Implementation Method 2
the stator windings generate opposing magnetic fields to rotate the rotor when current passes through the stator windings
Data Source
AI summary
A brushless DC motor includes a stator formed of a lamstack including a plurality of stacked laminations. The stator includes a plurality of radially extending core members and a circumferential wall. An intersection of each of the plurality of radially extending core members with the circumferential wall defines a flux null location, and a portion of the lamstack defines a first opening located at one of the flux null locations. The brushless DC motor includes a printed circuit board including a second opening and a grounding member including a first section received in the first opening of the stator and a second section received in the second opening of the printed circuit board to create a grounding path.