Stator Housing PCB Contact for Motor EMI Shielding
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Solution Overview
Problem
Electrical machines with electronics circuit boards outside the stator housing suffer from electromagnetic interference (EMI) radiation, which disrupts other electronics in motor vehicles, and the brush contact causes additional interference through the plastic transmission housing.
Innovation Solution
The electronics circuit board is designed to act as a shielding plate, directly contacting the metal stator housing, forming a Faraday cage with the carbon brushes, eliminating the need for additional shielding and effectively shielding EMI radiation up to 3 GHz by using a continuously conducting layer on the circuit board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the electronics circuit board is arranged radially outside the pole housing, then the electronics components can be accommodated separately, but electromagnetic interference radiation is emitted which disrupts other electronics functions
Solution Approach 1:
The electronics circuit board is integrated into the stator housing structure, merging the electronics accommodation function with the stator housing. The circuit board bears directly against the stator housing flange, forming a unified assembly that eliminates the need for a separate electronics housing while providing EMC shielding through the metal housing and continuous conductor layers.
Solution Approach 2:
The solution combines the insulating substrate of the circuit board with continuously conducting conductor layers (copper or aluminum) to create a composite structure. This composite material approach allows the circuit board to serve both as an electrical circuit carrier and as part of the EMC shielding system when contacted with the metal stator housing.
2Object-generated harmful factors
If additional sheet-metal shielding means is formed to eliminate EMC radiation, then electromagnetic interference is shielded, but the cost increases
Solution Approach 1:
The circuit board is designed to perform multiple functions: electrical circuit functionality, structural support, and EMC shielding. The continuously conducting conductor layers on the circuit board serve both electrical connection purposes and as part of the shielding system, eliminating the need for separate shielding components and reducing overall manufacturing cost.
Solution Approach 2:
The circuit board itself provides the shielding function through its continuously conducting conductor layers that extend to the edge and bear against the metal stator housing. The shielding capability is inherent in the circuit board design rather than requiring additional components, making the system self-sufficient for EMC protection.
3Object-generated harmful factors
If the electronics circuit board bears directly against the stator housing, then EMC shielding is achieved, but the central aperture for the rotor shaft requires additional shielding
Solution Approach 1:
Instead of providing continuous shielding across the entire circuit board, the solution applies local shielding only where necessary - around the central aperture in the end plate. This localized approach shields the critical area where the rotor shaft passes through while maintaining the overall shielding effectiveness and avoiding unnecessary complexity in non-critical areas.
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 design provides reliable EMI shielding without additional costly shielding components, maintaining a compact and mechanically stable motor design while allowing for high-frequency protection and easy assembly.
Implementation Method 1
the electronics circuit board can at the same time be used as a shielding plate which bears directly against the stator housing composed of metal. Here, the electronic components on the electronics circuit board are situated, just like the carbon brushes, inside the stator housing which, together with the electronics circuit board, forms a kind of Faraday cage which, as an EMC shielding means, shields the electromagnetic interference radiation that is produced to the outside
Data Source
AI summary
An electrical machine (10), in particular for the adjustment of movable parts in the motor vehicle, having a stator housing (22) which accommodates a stator (12) and a rotor (14), wherein the rotor (14) has a rotor shaft (20) on which a commutator (18) is arranged, which commutator can be energized by means of electrical brushes (20), and the stator housing (22) has an axial opening (24) with an encircling edge (26), through which axial opening the rotor shaft (16) protrudes out of the stator housing (22), wherein an electronics circuit board (PCB) (30), which is populated with at least one interference-suppression element (44), is arranged transversely in relation to the rotor shaft (16), and the electronics circuit board (30), in its circumferential region (31), bears against the edge (26) in a conductive manner in order to form a ground contact with the stator housing (22).