Detecting Turn Shorts in Rotor Windings: A New Test Using Magnetic Flux Monitoring

Šašić, M.; Stone, G.C.; Stein, J.; Stinson, Chris

doi:10.1109/mias.2012.2215644

Cited by 40 publications

(13 citation statements)

References 1 publication

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“…It is considered that the simplest way of determining the existence of shorted turns on the rotor pole windings is to measure the voltage drop across each pole (pole drop test) [16]. Disadvantages of this method are the following: the generator must be stopped and the partially disassembled, and preparation and measuring time is long, and since the rotor is not moving, there is no centrifugal force, so that it can happen that some shorted turns are not detected, because they are present only with the effect of centrifugal forces.…”

Section: Shorted Turns Detection and Air Gap Monitoringmentioning

confidence: 99%

“…In recent years, the implementation of on‐line monitoring of flux in the air gap of the hydrogenerators has started. The measurement of the flux of each rotor poles is performed, in order to discover the rotor pole that has shorted turns and determine its impact on the existence of a magnetic unbalance of the generator [16, 17]. This method is already widespread in large turbo generators [18, 19].…”

Section: Shorted Turns Detection and Air Gap Monitoringmentioning

confidence: 99%

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Fault detection algorithm used in a magnetic monitoring system of the hydrogenerator

Babic

Milić

Rakić

2017

IET Electric Power Applications

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In this study, the authors propose a fault detection algorithm used in an on-line magnetic monitoring system in the hydropower plant. The proposed algorithm is based on two magnetic measuring methods: measurement of (inner) flux within generator in air gap and measurement of stator leakage (outer) flux outside of the generator. The system has to ensure, in situ and real time, magnetic monitoring and fault detection of hydrogenerator. The monitoring system is also useful for modern maintenance approach such as a condition based maintenance without generators' work interruption and better planned and preventive maintenance in the power plant. The proposed system successfully detects the presence of magnetic unbalance of hydrogenerator, occurring as a consequence of shorted turns in the windings of the rotor poles or air gap asymmetry. The presented measurement results are achieved in real exploitation conditions.

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Section: Shorted Turns Detection and Air Gap Monitoringmentioning

confidence: 99%

Section: Shorted Turns Detection and Air Gap Monitoringmentioning

confidence: 99%

Fault detection algorithm used in a magnetic monitoring system of the hydrogenerator

Babic

Milić

Rakić

2017

IET Electric Power Applications

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“…Finally, the fourth type is the magnetic flux-based indexes. Either the magnetic flux is measured with a Gauss metre or a flux probe [20,21] or it is analysed using an analytical model [22]. Both torque measurements and magnetic flux measurements introduce an extra cost of the sensors.…”

Section: Introductionmentioning

confidence: 99%

Analysis and selection of harmonics sensitive to demagnetisation faults intended for condition monitoring of double rotor axial flux permanent magnet synchronous machines

Bisschop

Abdallh

Sergeant

et al. 2018

IET Electric Power Applications

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Yokeless and Segmented Armature (YASA) Axial Flux Permanent Magnet Synchronous Machines may have asymmetrical demagnetization defects in their two rotors. Condition monitoring therefore becomes more complicated than in conventional single rotor machines. In order to develop a real-time condition monitoring algorithm for demagnetization faults in YASA machines -which requires solving an inverse problem -a fast forward model is necessary. A frequency-based analytical model is used to calculate the three phase terminal voltages based on the three phase current waveforms and the demagnetization defects, including asymmetrical defects in the two rotors. In order to reduce the computational time of the forward model, the paper focuses on the sensitivity of different voltage harmonics on several demagnetization faults. To this end, the Cramér-Rao lower bound technique is used to analyse the harmonics sensitivity to the demagnetization faults. The goal of the sensitivity analysis is to select an appropriate set of harmonics that gives maximal information about the defects. It becomes much faster and useful for real-time condition monitoring. The results of the analysis show that the subharmonics around and including the fundamental are the most sensitive harmonics to the demagnetization defects. The analytical model is validated with experimental data and finite element simulations. IntroductionAxial flux permanent magnet synchronous machines (AFPMSMs) of the yokeless and segmented armature type (YASA) have been extensively used in different applications thanks to their excellent. Particularly, AFPMSMs are well dedicated for applications that acquire high power density, such as sustainable energy applications. In practice, these types of machines may suffer from different faults, such as rotor eccentricity and permanent magnet (PM) demagnetization, which decrease their reliability [4] [5]. In order to prevent the defect from progressing and creating more damage in the machine, online condition monitoring systems are highly needed to detect the faults in early stages. The demagnetization defects may occur due to an excessive temperature rise in the rotor of the machine, or due to high load currents or short circuit currents in the stator. When magnets are exposed to high temperatures, their magnetization may be lost partially or completely [6][7]. This problem can be mitigated by using magnets of a higher temperature class, but these magnets are more expensive and have a lower remanence. A better solution is to detect the demagnetization via a real-time monitoring system. Demagnetization faults can be detected on-line by several sensor and/or sensorless techniques. In [8] and [9], an overview of these techniques is given. Four types of detection techniques are identified. The first type consists of current-based indexes. Here the current waveforms are analysed in either the time or the frequency domain [10][11][12] [13]. Some techniques require machine standstill while others require steady-state operation. If ...

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“…Because of this, online monitoring methods have been developed. One well-known technique is the installation of probe coils on the stator inner wall to monitor the magnetic flux produced by the poles 1,2 . Because the probe needs to be installed on the air gap, the rotor must be removed to allow the sensor to be attached to the stator wall.…”

Section: Introductionmentioning

confidence: 99%

Development and field trial of a FBG-based magnetic sensor for large hydrogenerators

et al. 2016

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We propose a passive optical sensor for online magnetic field monitoring in large hydrogenerators, based on FBG (Fiber Bragg Grating) technology and a magnestostrictive material (Terfenol-D). The objective of this sensor is to detect faults in the rotor windings due to inter turn short-circuits. This device is packaged in a novel rod-shaped enclosure, allowing it to be easily installed on the ventilation ducts of the stator of the machine. This sensor was developed and tested in laboratory and it has been evaluated in a field test on a 200 MVA, 60 poles hydrogenerator.

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Detecting Turn Shorts in Rotor Windings: A New Test Using Magnetic Flux Monitoring

Cited by 40 publications

References 1 publication

Fault detection algorithm used in a magnetic monitoring system of the hydrogenerator

Fault detection algorithm used in a magnetic monitoring system of the hydrogenerator

Analysis and selection of harmonics sensitive to demagnetisation faults intended for condition monitoring of double rotor axial flux permanent magnet synchronous machines

Development and field trial of a FBG-based magnetic sensor for large hydrogenerators

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