Washer Shunt for Low-Inductance Current Measurement
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Solution Overview
Problem
High-power switching devices face challenges in measuring current transients due to the insertion of current measurement devices, which often introduce significant inductance and alter the transient being measured, particularly when placed between capacitor banks and modules.
Innovation Solution
A test and measurement accessory with a shunt structured as a washer, featuring a resistive portion and an insulative portion, minimizes the electrical path length and inductance by using a sense lead that runs through an inner opening, allowing for accurate current measurement without disrupting the magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current measurement device is inserted between the capacitor bank and the module, then current measurement is enabled, but significant inductance is introduced which alters the transient being measured
Solution Approach 1:
The shunt is nested within the existing electrical connection structure by integrating it into the busbar-to-module connection path. The shunt's inner conductor is positioned within the outer conductor, creating a compact nested configuration that minimizes spatial footprint and electrical path length while enabling current measurement without adding significant inductance to the transient circuit.
Solution Approach 2:
The measurement function is added in a different dimensional approach by using a coaxial structure where the sense lead runs through the innermost portion of the shunt. This three-dimensional arrangement allows the measurement path to be superimposed on the existing current path without extending the electrical path length, thereby avoiding additional inductance while enabling precise current measurement.
2Adaptability or versatility
If a traditional coaxial shunt is used, then DC capabilities and broad measurement bandwidth are achieved, but the shunt extends the electrical path such that unwanted inductance is inserted
Solution Approach 1:
The shunt is designed with localized functional zones: the outer conductor provides magnetic field containment and shielding in the region where it surrounds the inner conductor, while the inner conductor provides the measurement path. This local differentiation of functions allows the shunt to maintain DC capabilities and broad bandwidth through its coaxial geometry while minimizing overall electrical path length by confining the measurement function to the innermost portion where it intersects the current path.
Solution Approach 2:
The measurement function is merged with the existing electrical connection by integrating the shunt directly into the busbar-to-module connection path. The shunt's outer conductor serves as part of the current return path while the inner conductor provides the measurement path, combining multiple functions (current conduction, magnetic field shielding, and voltage sensing) into a single integrated component that does not extend the electrical path.
3Object-affected harmful factors
If the shunt minimizes electrical path length, then inductance insertion is reduced, but difficulty is increased in inserting the shunt into gaps in busbars
Solution Approach 1:
The shunt is segmented into distinct functional components: an outer conductor section that interfaces with the busbar connection, an inner conductor section that runs through the center for sensing, and insulating sections that separate these conductors. This segmentation allows each component to be optimized independently - the outer conductor can be designed to fit into busbar gaps while the inner conductor maintains the minimal electrical path length for low inductance, and the insulating sections facilitate assembly by providing mechanical clearance and electrical isolation.
Solution Approach 2:
Insulating materials are introduced as intermediary elements between the inner and outer conductors, and between the shunt and surrounding components. These insulating sections act as mediators that enable the compact nested configuration to be inserted into busbar gaps by providing mechanical clearance and electrical isolation, while not significantly increasing the electrical path length of the current-carrying conductors.
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 measures current transients with minimized inductance insertion, maintaining DC capabilities and broad bandwidth, while reducing magnetic flux pickup and measurement errors.
Implementation Method 1
constrain magnetic field between the outer and middle materials to cancel any inductance affecting the sense lead
Implementation Method 2
a resistive portion, the resistive portion configured to form a portion of the current path
Data Source
AI summary
A test and measurement accessory has a shunt configured to be located in a current path between a busbar and an electronic module and structured to minimize length added to the current path, the shunt having an opening extending through the shunt, and a resistive portion, the resistive portion configured to form a portion of the current path, and two or more contacts, at least one of the contacts extending through the opening and electrically insulated from the resistive portion of the shunt. A test and measurement accessory has a shunt, two or more contacts, at least one of the contacts extending through the opening, and a resistive portion comprising a plurality of resistors surrounding an insulative portion. A test and measurement accessory has a shunt including a washer having an opening, a resistive portion, and two or more contacts.