Low-Voltage Current Transformer Solution for High-Frequency Complex Waveform Scenarios

​Non-Contact Sensing System Based on Air-Core Rogowski Coil

HK Electrical
Yueqing HK Electrical Trading Co., Ltd.
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Core Solution Concept
Breaks through magnetic saturation limitations, utilizing the electromagnetic induction principle for innovative design. Achieves precise measurement of high-frequency currents, DC components, and high-order harmonics, solving the distortion issues of traditional iron-core CTs in complex waveform scenarios.

Technical Solution Architecture

  1. Sensing Unit: Flexible Air-Core Rogowski Coil

    • Structural Innovations

      • High-precision enameled wire uniformly wound on a non-magnetic flexible former (e.g., epoxy/engineering plastic)

      • Split-core mechanical design supporting live installation (suitable for retrofits and confined spaces)

    • Signal Generation Principle
      ⚠ Output Signal: di/dt (Current Differential Value)
      ➡ Directly reflects the current change rate, avoiding core hysteresis effects.

  2. Signal Processing Unit: High-Performance Integrator Circuit

Core Module

Technical Characteristics

Performance Indicators

Integrator Amplifier

Ultra-low input bias current (≤1pA)

Temp Drift: ±0.5μV/°C

Integration Capacitor

Polypropylene Film Capacitor (C0G grade)

Capacitance Stability >99%@ -40~125°C

Dynamic Compensation

Adaptive feedback network

Integrator Drift Suppression >40dB

Bandwidth Extension

Multi-stage active filtering

Freq. Response: DC ~ 1MHz

  1. ↳ Output Signal: Vout = k・I(t) (k is calibration factor, voltage linearly corresponds to current)

Core Advantages Over Traditional CTs

Pain Point Scenario

Limitations of Traditional Iron-Core CTs

Advantages of This Solution

High Short-Circuit Current

Measurement failure due to magnetic saturation

No magnetic saturation

DC Component

Cannot measure steady-state DC

Supports precise DC component measurement

High-Frequency Harmonics

High-frequency signal attenuation due to core losses

<0.5% distortion @ 100kHz harmonic

Complex Waveforms

Phase delay and waveform distortion

Group Delay <10ns

Installation Flexibility

Require power-off installation / Space-constrained

Flexible split-core design, 3-second deployment

Typical Application Scenarios

  1. Inverter Output Monitoring

    • Precisely captures high-frequency oscillations caused by IGBT switching (e.g., 20-150kHz)

    • Case: Harmonic analysis at a PV inverter plant, measurement error for 50th harmonic (2.5kHz) reduced from 12% to 0.8%.

  2. Arc Fault Detection

    • Nanosecond response to microsecond-level pulse currents during arc initiation (>100A/&mu;s)

    • Application: Arc protection in data center distribution cabinets, response time shortened to 300&mu;s.

  3. Electric Locomotive Traction Systems

    • Simultaneous analysis of DC supply components and PWM carrier signals (carrier freq. 2-5kHz)

    • Measured Data: Maintained Class 1 accuracy for DC 1500V + 4kHz ripple current.

Key Technical Parameters Summary

Item

Parameter

Measurement Range

10mA ~ 100kA (Peak)

Frequency Response

DC &ndash; 1.5MHz (-3dB)

Linearity Error

&le; &plusmn;0.2% FS

Mounting Bore

&Phi;50mm ~ &Phi;300mm (Customizable)

Operating Temp.

-40℃ ~ +85℃

Safety Certs.

IEC 61010, EN 50178

Solution Value Summary

Three-Dimensional Technological Breakthroughs:

  • Physical Layer Innovation: Air-core structure completely eliminates magnetic saturation risk, lifespan increased 10x.

  • Signal Layer Fidelity: 1MHz bandwidth + sub-microsecond response enables high-precision sensing for Energy IoT.

  • Engineering Layer Convenience: Split-core design reduces O&M downtime costs by 90%.

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