A Class D Power Amplifier for Multi-Frequency Eddy Current Testing Based on Multi-Simultaneous-Frequency Selective Harmonic Elimination Pulse Width Modulation

TL;DR

This paper presents a novel Class D power amplifier with multi-frequency selective harmonic elimination PWM for efficient, multi-frequency eddy current testing, demonstrating high MSF currents with low signal distortion.

Contribution

It introduces a new Class D amplifier design with MSF capability using a specialized PWM method, addressing efficiency and multi-frequency output challenges.

Findings

High MSF currents achieved with low distortion

Effective harmonic elimination demonstrated

Prototype verified with FPGA-based system

Abstract

Efficiency and multisimultaneous-frequency (MSF) output capability are two major criteria characterizing the performance of a power amplifier in the application of multifrequency eddy current testing (MECT). Switch-mode power amplifiers are known to have a very high efficiency, yet they have rarely been adopted in the instrumental development of MECT. In addition, switch-mode power amplifiers themselves are lacking in the research literature for MSF capability. In this article, a Class D power amplifier is designed so as to address the two issues. An MSF selective harmonic elimination pulsewidth modulation method is proposed to generate alternating magnetic fields, which are rich in selected harmonics. A field-programmable-gate-array-based experimental system has been developed to verify the design. Results show that the proposed methodology is capable of generating high MSF currents in the transmitting coil with a low distortion of signal.