Current-Shadow Busbar Layout for Accurate High-Current Sensing

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Solution Overview

Problem

Existing current measurement technologies, particularly shunts, face challenges in high current ranges due to phase errors caused by skin effects and induction, leading to inaccurate measurements and increased costs for compensation.

Innovation Solution

A one-piece busbar design with a resistance region and currentless measuring contact regions, featuring a current-shadow geometry and integrated temperature compensation, minimizes phase errors and enhances measurement accuracy by reducing the influence of mechanical and magnetic interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional shunts with press-fit pins are used for current measurement, then current measurement capability is achieved, but phase errors occur due to skin effects and induction in high current ranges

Engineering Contradiction:

Improvecurrent measurement accuracyVSAvoidphase errors from skin effects and induction

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The busbar is divided into functionally distinct regions: connection regions for current input/output, a resistance region for voltage measurement, and currentless regions for measuring contacts. This segmentation isolates the measuring contacts from the high-current path, eliminating phase errors caused by skin effects and induction while maintaining measurement capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A dedicated resistance region acts as an intermediary element between the connection regions. This region provides a controlled resistance for voltage measurement without carrying the full load current, thereby reducing the influence of harmful electromagnetic effects while enabling accurate current determination through voltage drop measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If measuring contacts are placed in high current regions, then current measurement is enabled, but mechanical effects cause transition resistance changes and measurement instability

Engineering Contradiction:

Improvevoltage measurement stabilityVSAvoidmeasurement consistency under mechanical effects

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The measuring contacts are extracted from the high-current carrying regions and placed in dedicated currentless regions. This removal eliminates the mechanical effects and transition resistance changes that occur under load, ensuring stable and reliable voltage measurements even when the busbar experiences mechanical stress or thermal expansion.

Inventive Principle:

Principle #2Taking out (Extraction)

3Loss of energy

If large cross-section resistance alloys are used to achieve low measuring resistance, then power loss is reduced, but voltage drops become very small (few millivolts) making measurement difficult

Engineering Contradiction:

Improvepower loss in shuntVSAvoidvoltage drop measurement sensitivity

Core Design Contradiction:

Loss of energyVSDifficulty of detecting and measuring

Solution Approach 1:

The busbar features a localized resistance region with specifically optimized dimensions and material properties. This region has a controlled, higher resistance compared to the low-resistance connection regions, creating a measurable voltage drop (e.g., 50 mV at rated current) without significantly increasing overall power loss. The local quality enhancement enables sensitive voltage measurement while maintaining low energy loss in the high-current path.

Inventive Principle:

Principle #3Local quality

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 provides precise and cost-effective current measurement with reduced phase and amplitude errors, suitable for high current applications, and allows for simpler manufacturing and assembly.

Implementation Method 1

A busbar for measuring a direct and/or alternating current... has connection regions and at least one resistance region arranged between the connection regions

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Implementation Method 2

measuring contacts... measure a voltage dropping across a resistance material, wherein from the dropping voltage and the resistance value of the resistance material a measuring circuit, using Ohm's law, determines a measure of the electric current

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Implementation Method 3

phase errors caused by skin effects and induction

Methodology Applied

Scientific EffectSkin Effect: Skin Effect

Implementation Method 4

phase errors caused by skin effects and induction

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Data Source

PatentUS20240110945A1Busbar for measuring a direct and/or alternating current

Publication Date: 2024.04.04 SMA SOLAR TECH AG

AI summary

A busbar for measuring a direct and/or alternating current has connection regions and at least one resistance region arranged between the connection regions, and two measuring contacts arranged in the resistance region. The busbar has a geometry in which the measuring contacts are currentless during operation of the busbar. The busbar is formed in one piece. An apparatus for determining current and having such a busbar and a power converter having such an apparatus are also disclosed.