Induction motor reliability in hoisting applications
Pynnönen, Antti (2019)
2019
Sähkötekniikka
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Hyväksymispäivämäärä
2019-05-22
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201904301446
https://urn.fi/URN:NBN:fi:tty-201904301446
Tiivistelmä
This thesis focuses on the study of different failure modes occurring in squirrel-cage induction motors used in hoisting applications. The goal is to gather information about the reliability of the studied hoisting motors and to identify their most potential failure modes. The research method utilizes the available statistical data gathered from the hoists operated in the field. This data is used to define failure distributions of the studied induction motors and to investigate their potential root causes.
The thesis also discusses basic operation principles of induction motors and frequency converters to increase the understanding of the occurring failure mechanisms. The studied induction motors are handled in two groups depending on their type of supply: direct on-line motors and variable frequency drive motors. Both motor groups are very similar but their characteristic failure modes differ from each other due to their differences in the supply and the operation.
The research part focuses on the data analysis of the available data sources. The data is gathered from multiple sources that are used for different purposes. One of the data sources is claim statistics that gives information about the failures occurring in the early stages of the motor service life. Moreover, the failures occurring in the later stages of the motor service life are studied by utilizing the maintenance statistics. These two data sources are used to define the hoisting motor failure distributions at the different stages of the service life. Furthermore, product and spare part sales statistics are used to search indications of possible reliability problems among the different motor types.
The root cause analyses are done by utilizing the remote monitoring data of the hoists. The monitoring data is used to investigate the usage history of the hoist which is crucial for identifying the root cause. For some hoists, this data can be tracked back to the failure statistics and opens the possibility of investigating specific fault cases. The data is used to identify any abnormalities in the usage of the hoist that can give indications about the potential causes of the failure. In addition, two reliability analysis methods, namely failure mode and effect analysis, and fault tree analysis, are used to further study the potential failure modes.
The thesis also discusses basic operation principles of induction motors and frequency converters to increase the understanding of the occurring failure mechanisms. The studied induction motors are handled in two groups depending on their type of supply: direct on-line motors and variable frequency drive motors. Both motor groups are very similar but their characteristic failure modes differ from each other due to their differences in the supply and the operation.
The research part focuses on the data analysis of the available data sources. The data is gathered from multiple sources that are used for different purposes. One of the data sources is claim statistics that gives information about the failures occurring in the early stages of the motor service life. Moreover, the failures occurring in the later stages of the motor service life are studied by utilizing the maintenance statistics. These two data sources are used to define the hoisting motor failure distributions at the different stages of the service life. Furthermore, product and spare part sales statistics are used to search indications of possible reliability problems among the different motor types.
The root cause analyses are done by utilizing the remote monitoring data of the hoists. The monitoring data is used to investigate the usage history of the hoist which is crucial for identifying the root cause. For some hoists, this data can be tracked back to the failure statistics and opens the possibility of investigating specific fault cases. The data is used to identify any abnormalities in the usage of the hoist that can give indications about the potential causes of the failure. In addition, two reliability analysis methods, namely failure mode and effect analysis, and fault tree analysis, are used to further study the potential failure modes.