EMI Filter with Selective Discharge Resistor for DC Networks
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Solution Overview
Problem
Existing electromagnetic interference (EMI) filters in electric systems, particularly in vehicles and industrial applications, face challenges in efficiently dissipating residual energy stored in reactive elements, leading to safety concerns and energy loss issues due to slow discharge rates and the use of bulky, expensive braking resistors.
Innovation Solution
A filter for DC electric networks with a selectively connectable power resistor between positive and negative terminals, integrated with a heat dissipator and a controlled switch, allowing for rapid energy dissipation and thermal management, which can be seamlessly integrated into existing EMI filters without significant size or cost increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a high ohmic value bleeding resistor is used to limit energy losses, then energy loss is reduced, but the discharge rate becomes slow
Solution Approach 1:
The patent applies a switching mechanism that dynamically changes the resistance value of the bleeding resistor. During normal operation, a high ohmic value is used to minimize energy losses. When rapid discharge is required, the switching mechanism connects a lower ohmic value resistor, increasing the discharge rate. This dynamic adjustment resolves the contradiction between limiting energy loss and achieving fast discharge rates.
2Speed
If a braking resistor is used to dissipate energy quickly, then discharge rate is improved, but the device becomes bulky, expensive, and requires substantial cooling
Solution Approach 1:
The patent integrates the bleeding resistor and switching mechanism directly into the EMI filter structure. The bleeding resistor is positioned to utilize the existing metallic enclosure of the EMI filter as a heat sink, eliminating the need for separate cooling systems. This merging of functions reduces device complexity, space requirements, and cost while maintaining rapid discharge capability.
Solution Approach 2:
The EMI filter's metallic enclosure serves multiple functions: it provides structural support, electromagnetic shielding, and thermal dissipation for the bleeding resistor. By making the enclosure multi-functional, the patent avoids adding dedicated cooling components, thereby reducing device complexity while enabling fast energy dissipation.
3Reliability
If a selectively connectable power resistor is integrated into the EMI filter, then discharge rate and safety are improved, but the filter complexity increases
Solution Approach 1:
The patent combines the bleeding resistor, switching mechanism, and control circuitry within the existing EMI filter housing. The resistor is electrically connected to the DC power line terminals, and the switching mechanism is integrated into the filter's internal circuitry. This consolidation improves safety by enabling rapid discharge without requiring a separate external discharge device, while the shared housing minimizes the increase in overall complexity.
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 solution enables rapid dissipation of residual energy, enhancing safety and reducing energy losses while providing cost and space savings by integrating an active discharge resistor within the EMI filter, effectively managing thermal and electrical requirements.
Implementation Method 1
a power resistor in the filter selectively connectable between one positive input or output terminal and one negative input or output terminal
Implementation Method 2
a heat dissipator or heat sink in thermal contact with the power resistor
Implementation Method 3
either directly, or through a metallic enclosure of the filter or through a busbar
Data Source
Figure 1~2
Figure 3~4
AI summary
A filter (50) for a DC electric network, comprising positive and negative input terminals (91a, 92a), and positive and negative output terminals (91b, 92b) for connecting the filter on a DC power line (15), a filtering circuit (51), arranged to filter out a noise component on the DC power line (15), characterized by a dissipative element (Rx) in the filter (50) selectively connectable between one positive input or output terminal (91a, 91b) and one negative input or output terminal (92a, 92b).