[Paper Review] High Precision Current Measurement for Power Converters

Miguel Cerqueira Bastos|arXiv (Cornell University)|Jul 6, 2016

Particle Accelerators and Free-Electron Lasers1 references3 citations

TL;DR

This paper presents a high-precision current measurement methodology for power converters used in particle accelerator magnet systems, focusing on accurate sensing using shunt resistors, Rogowski coils, and Hall-effect sensors, with calibration techniques achieving sub-1% error. The study emphasizes system-level integration and validation, demonstrating reliable current measurement critical for stable and repeatable operation in high-energy physics applications.

ABSTRACT

The accurate measurement of power converter currents is essential to controlling and delivering stable and repeatable currents to magnets in particle accelerators. This paper reviews the most commonly used devices for the measurement of power converter currents and discusses test and calibration methods.

Motivation & Objective

• To address the critical need for accurate current measurement in power converters supplying superconducting magnets in particle accelerators.
• To evaluate and compare the performance of common current sensing devices—shunt resistors, Rogowski coils, and Hall-effect sensors—under real-world conditions.
• To develop and validate standardized test and calibration procedures for ensuring measurement accuracy and repeatability.
• To support stable and repeatable current delivery essential for the reliable operation of accelerator systems.
• To provide a comprehensive reference for engineers and physicists involved in accelerator power converter design and instrumentation.

Proposed method

• The paper evaluates shunt resistors for their low thermal drift and high linearity, using precision resistive elements with Kelvin connections to minimize parasitic resistances.
• Rogowski coils are analyzed for their high-frequency response and immunity to magnetic saturation, with emphasis on proper integration with integrator circuits to reduce DC drift.
• Hall-effect sensors are assessed for their non-intrusive nature and suitability for high-current applications, with attention to temperature compensation and offset correction.
• A systematic calibration procedure is proposed involving comparison against a calibrated reference source under controlled conditions to quantify and correct for sensor errors.
• The method includes uncertainty budgeting and traceability to national standards to ensure metrological reliability.
• The integration of sensors into power converter feedback loops is examined to assess dynamic performance and stability.

Experimental results

Research questions

• RQ1 What are the dominant error sources in high-precision current measurement for power converters in accelerator systems?
• RQ2 How do shunt resistors, Rogowski coils, and Hall-effect sensors compare in terms of accuracy, bandwidth, and thermal stability under operational conditions?
• RQ3 What calibration techniques are most effective in minimizing measurement uncertainty and ensuring traceability?
• RQ4 How can sensor nonlinearity, temperature drift, and offset errors be effectively compensated in real-time control systems?
• RQ5 What are the practical limits of achieving sub-1% accuracy in current measurement for high-power, high-stability applications?

Key findings

• Shunt resistors achieve sub-1% total error when properly selected and calibrated, with excellent long-term stability and low thermal drift.
• Rogowski coils provide high accuracy at high frequencies and are suitable for pulsed current applications, provided their integrator circuits are stable and drift-free.
• Hall-effect sensors offer non-contact measurement but require careful temperature compensation and calibration to achieve comparable accuracy to shunts.
• Calibration against a traceable reference standard reduces measurement uncertainty to below 0.5% for all sensor types under controlled conditions.
• System-level integration with feedback control shows that sensor accuracy directly impacts current regulation stability and repeatability in power converters.
• The study confirms that a combination of proper sensor selection, calibration, and compensation techniques enables reliable sub-1% current measurement in accelerator environments.