Experimental investigation of frequency characteristics of large industrial DC machines with thyristor-based drives

DC machines continue to be widely used in many applications including mining. No comprehensive condition monitoring tools for large industrial DC machines are available on the market. The authors of this paper are involved in a research project supported by industry partners, which primary objective is to develop a DC Motor Duty meter envisaged as a predictive online condition monitoring tool for DC machines used in digging applications. Test facility constructed within this project and instrumentation of the motors were described in the previous year paper. This paper focuses on the analysis of experimental data obtained in steady state at different loading and speed. After initial evaluation of the machine steady state performance, spectral characteristics of the experimentally obtained armature current, armature voltage, flux density under the main pole and flux density in the commutation zone are developed. Frequency components revealed in the spectra are discussed with relation to their cause, role in brush and commutator wear and their importance for the condition monitoring tool development.