Motor Cable Shield Terminator for Common-Mode Noise Isolation
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Solution Overview
Problem
The breaking and re-termination of shielded cables between variable speed drives (VSDs) and electric motors can lead to noise emissions and decreased motor longevity due to high-frequency common mode currents, which are not effectively managed by existing technologies, especially in environments requiring high ingress protection ratings.
Innovation Solution
A terminator device that electrically connects the shield of the shielded cable to an electrically conductive motor housing, using a conductive housing and a housing conductor to isolate common mode currents and minimize noise emissions, while ensuring watertight connectivity and high IP ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If shielded cables are broken and re-terminated between VSDs and electric motors, then cable replacement or repair is achieved, but noise emissions increase and motor longevity decreases due to high-frequency common mode currents
Solution Approach 1:
The terminator device serves as an intermediary component between the shielded cable and motor housing. It includes a shield connector that receives the cable shield and a housing conductor that connects to the motor housing, creating an intermediate connection point. This intermediary structure allows for proper shield termination while maintaining electrical continuity and reducing common mode currents, thereby solving both the repairability need and the noise emission problem.
2Ease of operation
If existing termination technologies are used, then cable connections are achieved, but high-frequency common mode currents are not effectively managed
Solution Approach 1:
The terminator device segments the shielding function into distinct components: a shield connector portion that interfaces with the cable shield and a housing conductor portion that connects to the motor housing. This segmentation allows each component to be optimized for its specific function - the shield connector for receiving and isolating the cable shield, and the housing conductor for providing a low-impedance path to ground, thereby effectively managing common mode currents while maintaining ease of connection.
3Reliability
If shield connectors directly contact both cable shield and motor housing, then electrical connection is achieved, but watertight connectivity and high IP ratings are compromised
Solution Approach 1:
The terminator device introduces an intermediary sealed housing structure between the cable shield connection and the motor housing connection. The shield connector and housing conductor are contained within this sealed intermediate housing, which provides both electrical connection functionality and environmental sealing. This allows the device to maintain reliable electrical connectivity while protecting against moisture and contaminants, thereby achieving both electrical reliability and high IP ratings.
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 solution effectively reduces noise emissions and extends motor longevity by isolating high-frequency common mode currents, maintaining watertight connections, and meeting high ingress protection requirements.
Implementation Method 1
a shield connector configured to electrically connect (a) the shield of the shielded cable that is connected to the motor drive to (b) the electrically conductive housing
Implementation Method 2
a housing conductor that is electrically conductive and that includes: a first end that is directly connected to the electrically conductive housing; and a second end configured to be directly connected to the electrically conductive motor housing
Data Source
AI summary
A terminator device is configured to electrically connect a shield of a shield cable connected to a motor drive to an electrically conductive motor housing of an electric motor. The terminator device includes: an electrically conductive housing; a shield connector configured to electrically connect (a) the shield of the shielded cable that is connected to the motor drive to (b) the electrically conductive housing; a housing conductor that is electrically conductive and that includes: a first end that is directly connected to the electrically conductive housing; and a second end configured to be directly connected to the electrically conductive motor housing of the electric motor.