Mababang Kostong Solusyon sa Pagganap ng Current: Ang Precision Shunt Nagpapalit ng mga Tradisyonal na Low-Voltage Current Transformers

I. Paliwanag sa Background ng Solusyon
Naroon ang malubhang pangangailangan para sa mababang gastos na pagmamasid ng kasalukuyan sa mga aplikasyon sa industriyal na kontrol, pagsukat ng enerhiya, at proteksyon laban sa sobrang kasalukuyan, ang mga tradisyonal na electromagnetic current transformers (CTs) at Hall sensors ay nagbibigay ng mga isyu tulad ng mataas na gastos sa materyales (lalo na para sa >30A specifications) at komplikadong proseso ng paggawa. Ang solusyong ito ay gumagamit ng apat-na-terminal na manganin shunt resistor + optimized signal chain design upang makamit ang ekstremong kontrol ng gastos sa mga scenario ng high-volume application.

II. Core Solution Design

Sensing Unit

Precision Four-Terminal Manganin Shunt Resistor

Nagpapalit sa tradisyonal na CT core at coil structure.
Mga Pangunahing Parameter: 50μΩ-5mΩ resistance range (customized per current rating), Temperature Coefficient <50ppm/°C.
Ang apat-na-terminal na istraktura ay nasisira ang error sa contact resistance (Kelvin connection).

Signal Processing Chain

Low-Drift Instrumentation Amplifier (INA)

Gumagamit ng mga device na may <0.5μV/°C offset voltage drift (e.g., AD8237, INA826).
Gain Error <0.1%, CMRR >120dB (suppresses common-mode interference).
Integrated EMI filtering reduces peripheral circuitry.

Isolation Optimization

Switched Capacitor Isolator (e.g., ADI isoPower®)

Nagpapalit sa magnetic isolation structure ng tradisyonal na CT.
Sumusuporta sa >5kV DC isolation voltage.
40% mas mababa ang power consumption, cost only 60% of optocoupler solutions.

Mechanical Design

Injection-Molded Plastic Housing

Nagbabawas ng metal shielding layers at potting process.
Nagpapanatili ng IP54 protection rating (dustproof and water splash resistant).
Standardized pluggable terminals for automated assembly.

III. Cost Advantage Analysis (vs. Traditional Solution)

Item	Traditional CT Solution	This Shunt Solution	Reduction/Increase
100A Sensor BOM Cost	$8.2	$1.7	79%↓
Daily Production Line Capacity	5,000 pcs	22,000 pcs	340%↑
Calibration Time/Piece	45 sec	8 sec	82%↓
High-Current Spec Premium	300%	20%	-

IV. Typical Technical Specifications

Accuracy: 1% FS (@25°C), 2% FS (@-40°C~+85°C)
Bandwidth: DC~50kHz (superior to traditional CT's 10kHz limit)
Rated Current: 15-300A (>300A recommended using parallel shunt arrays)
Power Consumption: <15mW (no self-heating impact)
Response Time: <1μs (significant advantage in overcurrent protection scenarios)

V. Application Scenario Adaptation

Smart Meter Internal Measurement

Suitable for energy metering below Class 1.
Busbar current sampling (paired with Σ-Δ ADC).

Motor Drive Control Systems

Three-phase inverter phase current detection.
Cost-sensitive BLDC controllers.

Overcurrent Protection Devices

Breaker trip current detection.
Response speed improved by 50x.

Solar Inverters

String current monitoring (DC side).
Eliminates traditional CT's residual flux error issue.

VI. Implementation Key Points

Thermal Management Design

Copper pour heat dissipation (PCB acts as heat sink).
Rule to follow: ≥4mm² copper pour per 1A current.

EMC Optimization

Differential trace length matching ≤10mm.
π-filter at instrumentation amplifier front end.

Mass Production Control

Fully automated laser resistor trimming calibration.
Temperature compensation coefficient firmware programming.
Dynamic load testing (replaces traditional burn-in process).

Solution Limitations:

Not suitable for >600V strong isolation scenarios (requires reinforced isolation solution).
Significant copper losses at currents >500A (recommend magnetic solution).

07/21/2025

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