Abstract
Future health monitoring concepts in different fields of engineering require reliable fault detection to avoid unscheduled machine downtime. Diagnosis of electrical induction machines for industrial applications is widely discussed in literature. In aviation industry, this topic is still only rarely discussed. A common approach to health monitoring for electrical induction machines is to use Motor Current Signature Analysis (MCSA) based on a Fast Fourier Transform (FFT). Research results on this topic are available for comparatively large motors, where the power supply is typically based on 50Hz alternating current, which is the general power supply frequency for industrial applications.
 In this paper, transferability to airborne applications, where the power supply is 400Hz, is assessed. Three phase asynchronous motors are used to analyse detectability of different motor faults. The possibility to transfer fault detection results from 50Hz to 400Hz induction machines is the main question answered in this research work. 400Hz power supply frequency requires adjusted motor design, causing increased motor speed compared to 50Hz supply frequency. The motor used for experiments in this work is a 800W motor with 200V phase to phase power supply, powering an avionic fan. The fault cases to be examined are a bearing fault, a rotor unbalance, a stator winding fault, a broken rotor bar and a static air gap eccentricity. These are the most common faults in electrical induction machines which can cause machine downtime. The focus of the research work is the feasibility of the application of MCSA for small scale, high speed motor design, using the Fourier spectra of the current signal.
 Detectability is given for all but the bearing fault, although rotor unbalance can only be detected in case of severe damage level. Results obtained in the experiments are interpreted withrespect to the motor design. Physical interpretation are given in case the results differ from those found in literature for 50Hz electrical machines.
Highlights
Health monitoring has gained major attention in various sectors of engineering over the last two decades
As an example, (Thomson & Gilmore, 2003) exposes the financial and production losses due to unscheduled downtime of production plants, where large size induction motors are often used. This argumentation can be transferred to the aviation sector, where unscheduled maintenance due to malfunction of small size induction motors potentially forces the aircraft to stay on ground
The above mentioned publications have in common, that fault diagnosis based on Motor Current Signature Analysis (MCSA) is examined using 50Hz or in a few cases 60Hz power supply systems, as they are used for industrial applications
Summary
Health monitoring has gained major attention in various sectors of engineering over the last two decades. Sensor reliability is not degraded because of the above mentioned reasons These advantages of the current sensors led to high quality publications of numerous research results in the field of motor current signature analysis (MCSA). The above mentioned publications have in common, that fault diagnosis based on MCSA is examined using 50Hz or in a few cases 60Hz power supply systems, as they are used for industrial applications. This electric frequency results in slow motor speed. The airborne power supply system is still mostly based on 400Hz alternating current This leads to adapted design of induction motors, resulting in smaller motors with faster rotor speed. This work includes five different fault cases, i.e. bearing fault, rotor unbalance, stator winding fault, broken rotor bar and static air gap eccentricity
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