Model-based eccentricity diagnosis for a ship brushless-generator exploiting the Machine Voltage Signature Analysis (MVSA)

Detection of Eccentricity Faults in Induction Machines Based on Nameplate Parameters

“…Although substantial research has been conducted in this area with regard to the effect of load on low-frequency sidebands with mixed eccentricity [8], [9]; pure dynamic eccentricity [10]; a thorough FE study of mixed eccentricity [11]; stray flux [12]; increase in transient leakage reactance [13]; detection of mixed eccentricity using complex apparent power for utility [14] and inverter-fed drives [15]; Hilbert transform and motor current demodulation analysis [16], [17]; fuzzy logic [18]; spectrum analysis of stator current, voltage, and stator direct-axis current of a dual stator induction motor for eccentricity faults [19]; discrete-wavelet-transform-based MCSA of mixed eccentricity [20]; reluctance mesh modeling of induction motor with eccentricity [21]; noise reduction in mixed eccentricity fault detection using autocorrelation [22]; and their detection in motors driven from voltage source inverter-pulse width modulated inverters [23], [24], this basic issue is yet to be resolved. More literature surveys in the area of eccentricity-fault diagnosis of brushless dc motors using analytic wavelet ridge [25] and using FE analysis of permanent-magnet synchronous motors [26] and regular synchronous machines [27], [28] also did not reveal anything significant.…”

DIEM project's outcomes: An automated air-gap monitoring approach for Italian Navy's on-board low-voltage generators

“…Dynamic REs incur due to a misaligned coupling flange between generator and prime mover (diesel engine), Fig. 2, or to UMP and bent axis [6]. Since the ship's structure is mechanically and thermally solicited, the drawbacks above are usually more prominent than in on shore installations.…”

“…Development of models for simulation of eccentric-rotor synchronous machines: Dynamic numerical models based on winding function approach (WF A) and on time-stepping [mite-element method (TSFEM) were carried out for round rotor and salient-pole machines used on-board and in laboratory. The simulations allowed in-depth investigation of phase voltages, phase currents, and internal currents in various load and eccentricity fault conditions [6], [17], [18], [8]. The internal currents finally appeared as the best means for RE diagnosis, and the complex internal current space vectors were elected as main analysis tools.…”

“…Insulation and air gap checks are commonly routinely performed on board for generator preventive maintenance. The air-gap is manually checked by using long metal strips (OA-1m) through apposite slots in the generator front-cover [6], Fig. l.…”

“…Many 978-1-4673-1372-8/12/$31.00 ©2012 IEEE drawbacks were evidenced in this procedure: a) The machine must be turned off and disconnected; b) The dynamic eccentricity due to UMP cannot be detected when the field winding is disabled; c) The procedure is fatiguing and slow; d) The procedure is off-line and only periodically carried out; e) Measurement errors due to the operator are unavoidable; t) Sometimes the measurement is impossible, due to mechanical obstacles/obstructions; g) The results are difficult to analyze; h) Sometimes no data about the air gap is furnished by the manufacturer; i) The procedure is quite different from machine to machine, depending on machine size, position, number of poles, presence of co-axial exciter machine, number and location of slots, bearing type, etc., so a unified approach is not available to define a standard procedure. To overcome the drawbacks inherent to the manual measurements [6], a Research Program focused on the Diagnostics of on-board Electric Machineries (DIEM) and comprised in the Military Research National Program was started to carry out a solution [7]. An innovative method for rotor eccentricity (RE) detection based on measurement of internal currents in armature windings with parallel connections has been so developed [8], [9].…”