Noninvasive Flexible Current Probe as a Diagnosis Tool Inside a PWM Chopper Module

Traditional noncontact rigid probes fail to meet the time-domain reconstruction requirements inside industrial modules in an enclosed chamber. In this article, a flexible current probe is proposed as a diagnosis tool to extend the noninvasive time-varying current reconstruction technology inside an industrial PWM-chopper module in an enclosed chamber. The flexibility of the probe allows for direct placement on trace surfaces or attachment to trace sides for current measurement without intrusion. Reflection coefficient curves obtained at typical bending angles demonstrate remarkable consistency with an average error of 0.63%. Furthermore, time-domain curves of reconstructed currents closely match directly measured currents with an average error below 0.24%. The flexible probe demonstrates consistent and stable performance across different bending levels in noninvasive current measurement tests. In the application tests, the experimental results validate its utility as a diagnostic tool for noninvasive time-varying current detection within an industrial PWM-chopper module, achieving an average error below 0.11%. Additionally, the proposed probe enables the detection of varying output currents for load failure analysis in constant voltage output modules.

I. Introduction

Industrial module failure diagnostic tests are important for ensuring the reliability and safety of industrial electronic modules [1], [2], [3], [4], [5]. The popular electromagnetic immunity diagnostic tests include surge immunity tests (SITs), electrical fast transient/burst tests (EFTs), direct power injection tests (DPIs), and source-conducted emission tests (ISO 7637-2). In these electromagnetic immunity diagnostic tests, it is expected to monitor the interfered voltage or current in the transmission lines on the tested modules.