Inter-system Ground Capacitors for Drive Device Noise Reduction
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Solution Overview
Problem
Drive devices, which integrate a motor and electronic control unit (ECU) in a single housing, face challenges in preventing the propagation of electrical noise outside the device, particularly in redundant configurations where shared grounds can lead to noise exchange and propagation to other vehicle components.
Innovation Solution
The implementation of a drive device with inter-system ground connection capacitors and electro-mechanical connection capacitors that connect the grounds of separate systems to a common housing, creating a low impedance path to return noise back to the noise source, thereby limiting its propagation outside the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grounds for separate systems are isolated from one another, then system electrical independence is improved, but electrical noise propagates outside the drive device to other vehicle components
Solution Approach 1:
A ground isolation capacitor is introduced as an intermediary component between the first ground and the second ground. This capacitor allows electrical noise to be blocked while maintaining a reference potential connection, thus preventing noise propagation to external vehicle components while preserving system electrical independence. The capacitor acts as a frequency-dependent barrier that isolates DC ground potentials while blocking high-frequency noise signals.
Solution Approach 2:
The ground connection impedance is dynamically changed by using a capacitor whose impedance varies with frequency. At DC and low frequencies, the capacitor maintains low impedance for potential reference, while at high frequencies (noise range), the impedance becomes very high, effectively blocking noise propagation. This parameter change enables the ground system to adapt its electrical characteristics based on signal frequency.
2Volume of moving object
If drive device components are integrated in one housing, then device compactness is improved, but electrical noise generation and propagation increase
Solution Approach 1:
The integrated housing is segmented into distinct system regions (first system and second system) with separate ground domains. The ground isolation capacitor creates an electrical boundary between these regions, preventing noise generated in one system from propagating to other systems within the same housing. This internal segmentation allows compact integration while maintaining electrical isolation to suppress noise.
Solution Approach 2:
The ground isolation capacitor serves as an intermediary element within the integrated housing that mediates between different system grounds. It allows the housing to remain compact and integrated while introducing a noise-blocking interface between systems. The capacitor enables physical integration without electrical integration, thus reducing noise propagation despite close component proximity.
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 effectively reduces noise transmission to the vehicle, improving noise reduction performance and maintaining a compact, cost-effective design for the drive device.
Implementation Method 1
inter-system ground connection capacitors that connect the grounds of separate systems to a common housing
Implementation Method 2
creating a low impedance path to return noise back to the noise source
Implementation Method 3
electro-mechanical connection capacitors that connect the grounds of separate systems to a common housing
Data Source
AI summary
A drive device for use in a vehicle includes a motor, a substrate, and at least one inter-system ground connection capacitor. The motor includes a plurality of motor windings within one housing. Multiple inverters are mounted on the substrate. Each inverter is connected to a different battery and a different ground to form a system, where each of the motor windings is associated with its own system. The inter-system ground connection capacitor is mounted on the substrate, and electrically connects the grounds of the systems together to reduce electrical noise propagated outside the drive device to other parts in the vehicle.