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. 2023 Feb 26;23(5):2583.
doi: 10.3390/s23052583.

Online SFRA for Reliability of Power Systems: Characterization of a Batch of Healthy and Damaged Induction Motors for Predictive Maintenance

Giovanni Bucci  1 , Fabrizio Ciancetta  1 , Andrea Fioravanti  1 , Edoardo Fiorucci  1 , Simone Mari  1 , Andrea Silvestri  1
Affiliations

Online SFRA for Reliability of Power Systems: Characterization of a Batch of Healthy and Damaged Induction Motors for Predictive Maintenance

Giovanni Bucci et al. Sensors (Basel). .

Abstract

Asynchronous motors represent a large percentage of motors used in the electrical industry. Suitable predictive maintenance techniques are strongly required when these motors are critical in their operations. Continuous non-invasive monitoring techniques can be investigated to avoid the disconnection of the motors under test and service interruption. This paper proposes an innovative predictive monitoring system based on the online sweep frequency response analysis (SFRA) technique. The testing system applies variable frequency sinusoidal signals to the motors and then acquires and processes the applied and response signals in the frequency domain. In the literature, SFRA has been applied to power transformers and electric motors switched off and disconnected from the main grid. The approach described in this work is innovative. Coupling circuits allow for the injection and acquisition of the signals, while grids feed the motors. A comparison between the transfer functions (TFs) of healthy motors and those with slight damage was performed with a batch of 1.5 kW, four-pole induction motors to investigate the technique's performance. The results show that the online SFRA could be of interest for monitoring induction motors' health conditions, especially for mission-critical and safety-critical applications. The overall cost of the whole testing system, including the coupling filters and cables, is less than EUR 400.

Keywords: custom instrumentation; frequency response; induction motors; industrial measurements; measurement system; predictive maintenance.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Block diagram of the experimental setup.
Figure 2
Figure 2
The testing bench.
Figure 3
Figure 3
SFRA online TF of the supply system only, measured on line-to-line terminals.
Figure 4
Figure 4
SFRA online motor 1 at various load percentages after 1 h of full load service.
Figure 5
Figure 5
Reference TF processed at 0% load.
Figure 6
Figure 6
Reference TF processed at 25% load.
Figure 7
Figure 7
Reference TF processed at 50% load.
Figure 8
Figure 8
Reference TF processed at 75% load.
Figure 9
Figure 9
Reference TF processed at 100% load.
Figure 10
Figure 10
Overall reference TFs processed with the whole dataset.
Figure 11
Figure 11
Comparison between TFs of the same motor in healthy conditions and with a 1 Ω resistance-in-series on a phase conductor.
Figure 12
Figure 12
Comparison of the TF of a motor with a 1 Ω resistance-in-series on a phase conductor with the reference TFs on the whole bandwidth.
Figure 13
Figure 13
Comparison between TFs of the same motor in healthy conditions and with a 25 kΩ resistance between one terminal and the ground.
Figure 14
Figure 14
Comparison of the TF of a motor with a 25 kΩ resistance between one terminal and the ground with the reference TFs.
Figure 15
Figure 15
Induction motor with slight rotor misalignment.
Figure 16
Figure 16
Comparison between TFs of the same motor in healthy conditions and with slight rotor misalignment.
Figure 17
Figure 17
Comparison between the TF of the motor with slight rotor misalignment and the reference TFs.
Figure 18
Figure 18
Comparison between TFs of the same motor in healthy conditions and after overheating.
Figure 19
Figure 19
Comparison of the TF of a motor after overheating with the reference TFs.
Figure 20
Figure 20
The stator of an induction motor after a fall from a height of 1 m.
Figure 21
Figure 21
Comparison between TFs of the same motor in healthy condition and a stator fell from a height of 1 m.
Figure 22
Figure 22
Comparison of the TF of a motor after the stator fell from a height of 1 m with the reference TFs.
Figure 23
Figure 23
Shorting ring damage.
Figure 24
Figure 24
Comparison between TFs of the same motor in healthy conditions and with shorting ring damage.
Figure 25
Figure 25
Comparison between the TF of a motor with shorting ring damage and the reference TFs.
Figure 26
Figure 26
Comparison between TFs of the same motor in healthy conditions and with rotor bar damage.
Figure 27
Figure 27
Comparison of the TF of a motor with shorting ring damage with the reference TFs.
Figure 28
Figure 28
Rotor group fall.
Figure 29
Figure 29
Comparison between TFs of the same motor in healthy conditions and after the rotor group fell from a height of 1 m.
Figure 30
Figure 30
Comparison of the TF of a motor after the rotor group fell from a height of 1 m with the reference TFs.
Figure 31
Figure 31
Insulating enamel removed.
Figure 32
Figure 32
Welded winding turns.
Figure 33
Figure 33
Comparison between TFs of the same motor in healthy conditions and with a shortcut between 2 winding turns.
Figure 34
Figure 34
Comparison between the TF of a motor with a shortcut between 2 winding turns and the reference TFs.
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