Method, system, and computer-readable medium for sensorless measurement of induction machine rotor bar pass frequency

A method for sensorless measurement of induction machine (22) speed, the method comprising:

• (a) sampling a current waveform of the induction machine at a sampling frequency higher than a fundamental frequency of the induction machine to obtain sampled points;
• (b) characterizing the sampled current over a selected first time window comprising a multiple of a fundamental period of the induction machine to obtain characterized points;
• (c) subtracting the characterized points from respective sampled points to obtain a residual signal comprising residual points;
• (d) obtaining a frequency spectrum representative of the residual signal over a selected second time window, wherein a beginning of the second time window is defined by a selected point;
• (e) multiplying an approximate speed by the number of rotor bars of the machine to obtain an approximate bar pass frequency;
• (f) obtaining at least one significant side band of the approximate bar pass frequency;
• and
• (g) obtaining a rotor bar pass frequency from the at least one significant side band.
• (h) obtaining an induction machine speed from the rotor bar pass frequency.

A system comprising a computer configured for:

• (a) sampling a current waveform of an induction machine to obtain sampled points;
• (b) characterizing the sampled current over a selected first time window to obtain characterized points;
• (c) subtracting the characterized points from respective sampled points to obtain a residual signal comprising residual points;
• (d) obtaining a frequency spectrum representative of the residual signal over a selected second time window;
• and
• (e) identifying a rotor bar pass frequency from the frequency spectrum.

A computer-readable medium storing computer instructions for instructing a computer, the computer instructions comprising:

• (a) sampling a current waveform of an induction machine to obtain sampled points;
• (b) characterizing the sampled current over a selected first time window to obtain characterized points;
• (c) subtracting the characterized points from respective sampled points to obtain a residual signal comprising residual points;
• (d) obtaining a frequency spectrum representative of the residual signal over a selected second time window;
• and
• (e) identifying a rotor bar pass frequency from the frequency spectrum.