23rd IMEKO TC 4 International Symposium and the 5th Chinese Conference on Electromagnetic Metrology Technical (IMEKO TC4 2019)

163 / 2019-03-15 21:54:26

Detecting cracks on graphite commutators using estimated amplitude of resistance

Resistance,DFT,frequency,amplitude,estimatio

Plenary track > Waveform Analysis and Measurements

In this paper, the method for detecting cracks on graphite commutator with resistance measurement is described. Resistance is measured with four-point resistance measurement method when commutator is rotated. Result of measurement is surface resistance profile of graphite from which a cracks can be recognized. Information of the crack on the commutator graphite surface is hidden in the amplitude behaviour of a strongly distorted signal. Since the period of the amplitude changing is not constant the interpolation DFT algorithm is used first to estimate the current period along the turn of the rotated commutator around its axis and upon this the amplitude of the fundamental component. The amplitude estimation is achieved with only one DFT coefficient at for an almost coherent measurement interval of one period. Behaviour of the amplitude changing shows that the commutator with crack has specific increase of the amplitude around peak value and frequencies of the amplitude distribution can be used for the reliably checking of the crack presence.