Control Circuit with Segmented Return Conductors for Interference Reduction
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Solution Overview
Problem
Electrical drive devices experience high interference emissions due to dramatic changes in control circuit and back-up circuit currents, leading to voltage drops and highly dynamic currents flowing through the housing, which are not filtered, resulting in elevated emission measurements.
Innovation Solution
A control circuit with two separate return conductors is implemented, where the back-up circuit and control circuit currents flow through the first return conductor, and a separate ground terminal is connected to a second return conductor at a single point, confining these currents to a defined space and preventing them from flowing through the housing, thereby reducing interference emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single return conductor is used for both control circuit and back-up circuit, then the circuit structure is simple, but high interference emissions occur due to voltage drops driving dynamic currents through the housing
Solution Approach 1:
The single return conductor is segmented into two separate return conductors: a first return conductor for the control circuit and a second return conductor for the back-up circuit. This segmentation prevents the mixing of control circuit currents and back-up circuit currents, eliminating the voltage drops that drive interference emissions through the housing while maintaining manageable circuit complexity through systematic separation.
Solution Approach 2:
The back-up circuit current path is extracted from the common return conductor and routed through a separate second return conductor. This extraction removes the source of voltage drops and dynamic currents from the housing circuit, eliminating interference emissions while preserving the essential grounding function through the separated path.
2Stability of the object's composition
If return conductors are connected at multiple points, then the reference potential is more uniform, but currents flow through the housing creating interference emissions
Solution Approach 1:
The multiple connection points are segmented into exactly one connection point for the first return conductor and exactly one connection point for the second return conductor. This segmentation ensures that each return conductor has a unique, dedicated path to the housing, preventing current mixing while maintaining stable reference potentials through the separated, well-defined connection points.
3Device complexity
If control circuit currents and back-up circuit currents flow through the same return conductor, then the wiring is simplified, but voltage drops cause highly dynamic currents to flow through the housing
Solution Approach 1:
The shared return conductor is segmented into two distinct return conductors with separate paths. The first return conductor carries only control circuit currents, while the second return conductor carries only back-up circuit currents. This segmentation eliminates the voltage drops that occur when both current types share a common path, preventing the generation of highly dynamic currents through the housing.
Solution Approach 2:
The back-up circuit current path is extracted from the control circuit return path. By routing back-up circuit currents through a separate second return conductor, the voltage drops affecting the control circuit are eliminated, and the housing is protected from dynamic currents while maintaining simplified wiring through systematic current separation.
Data Source
AI summary
An electrical drive device (1) includes a control circuit (3) connectable to a voltage source (5) on the input side and to an electric drive motor (4) on the output side. The control circuit (3) includes two separate return conductors (13, 35) connected to each other at a single connection point (36). One return conductor (13) is connected to the ground terminal (12) of the control circuit (3). The other return conductor (35) is connected to a motor converter (14), a converter control (15) and a back-up capacitor (19). Due to this arrangement, the currents (is, ia) flowing in a back-up circuit loop (31) and a control circuit loop (32) are confined to remain within the control circuit (3) and are separated from a housing (10), for example the chassis of a motor vehicle. As a result, the electrical drive device (1) has low interference emissions.