Original scientific paper
https://doi.org/10.37798/202069451
Static eccentricity fault detection method for electrical rotating machines based on the magnetic field analysis in the air gap by measuring coils
Stjepan Tvorić
; University of Applied Sciences, Zagreb Croatia
Miroslav Petrinić
; KONČAR – Electrical Engineering Institute Croatia
Ante Elez
; KONČAR – Generators and Motors Croatia
Mario Brčić
; KONČAR – Generators and Motors Croatia
Abstract
Electrical rotating machines have a great economic significance as they enable conversion of energy between mechanical and electrical state. Reliability
and operation safety of these machines can be greatly improved by implementation of continuous condition monitoring and supervisory systems.
Especially important feature of such systems is the ability of early fault detection. For this reason, several methods for detection and diagnosis
of the machine faults have been developed and designed. As fault detection methods can largely differ in the types of detectable faults, machine
adoptability and price of the system, a novel method was developed that can be used for cost-effective detection of various faults of electrical machine.
Machine fault detection technique presented in this paper is based on the measurement of magnetic field in the air gap. Numerous studies
have proven that crucial information about the machine condition can be determined based on measurement and analysis of the magnetic field in the
air gap. It has also been confirmed that analysis of the air gap magnetic field can be used to detect, diagnose and recognize various electrical faults
in their very early stage. Proposed method of positioning and installation of the measuring coils on ferromagnetic core parts within the air gap region
of the machine enables differentiation of various faults. Furthermore, different faults can be detected if measuring coils are placed on the stator teeth
then when placed on the rotor side. The paper presents method on how to analyse and process the measured voltages acquired from measuring
coils placed within the machine, especially in the case of rotor static eccentricity detection. The methodology is explained by means of finite element
method (FEM) calculations and verified by measurements that were performed on the induction machine. FEM calculation model was used to predict
measurement coil output of the induction motor for healthy and various faulty states (at different amounts of static eccentricity). These results were
then confirmed by measurements performed in the laboratory on the induction traction motor that was specially modified to enable measurements
of faulty operation states of the machine. Measurements comprised of several machine fault conditions broken one rotor bar, broken multiple rotor
bars, broken rotor end ring and various levels of rotor static eccentricity.
Other methods used for faults detection are primarily based on the monitoring of quantities such as current and vibration and their harmonic analysis.
This new system is based on the tracing the changes of induced voltage of the measuring coils installed on the stator teeth. Faults can be detected
and differentiated based on RMS value of these voltages and the number of voltage spikes of voltage waveform i.e. without the need of harmonic
analyses. If these coils are installed on the rotor it is possible to detect the stator winding faults in a similar manner.
Keywords
Hrčak ID:
261837
URI
Publication date:
31.12.2020.
Visits: 788 *