Improved Quadratic Time-frequency Distributions for Detecting Inter-turn Short Circuits of PMSMs in Transient States

Author's accepted manuscript.© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.acceptedVersio

Non-uniqueness up to the Onsager threshold for the forced SQG equation

We establish new non-uniqueness results for the forced inviscid surface quasi-geostrophic equation, via an alternating formulation of convex integration techniques. Our results imply non-uniquenesss in the class of weak solutions with $|\nabla|^{-1}\theta\in C_tC_x^\alpha$, for any $\alpha<1$.Comment: 22 page

RMS Based Health Indicators for Remaining Useful Lifetime Estimation of Bearings

Estimating the remaining useful life (RUL) of bearings from healthy to faulty is important for predictive maintenance. The bearing fault severity can be estimated based on the energy or root mean square (RMS) of vibration signals, and a stopping criterion can be set based on a threshold given by an ISO standard. However, the vibration RMS is often not monotonically increasing with damage, which renders a challenge for predicting the RUL. This study proposes a novel method for splitting the vibration signal into multiple frequency bands before RMS calculations to generate multiple health indicators. Monotonic health indicators are identified using the Spearman coefficient, and the RUL is afterward estimated for each indicator using a suitable model and parameter update scheme. Historical failure data is not required to set any parameters. The proposed method is tested with the Paris' law, where parameters are updated by particle filters. Experimental results from two test rigs validate the performance of the proposed method.publishedVersio

Resistive Loss Modelling for Inverter-fed Induction Motors

The aim of this research is to model resistive losses in induction motors. The resistive losses in the form-wound stator windings of induction motors were modelled by using time-discretized finite element analysis (FEA) and circuit models. Loss modelling with a high level of accuracy by means of FEA can be used in the demanding design of electrical machines, typically for high-power and high-speed induction motors in spite of its high computational cost. Alternatively, the equivalent circuits served as a cheap computational tool for the rapid estimation of the resistive losses of 37-kW and 1250-kW machines for motor drives without using the machine data, typically the machine structure and materials. Electromagnetic losses lead to a temperature rise in electrical machines. As a result, temperature rise analysis is required to check whether the induction motors that are designed fulfill the IEC standard or design constraints. Thermal analysis employs FEA or a thermal network depending on the specific problems being studied. In this study, Finite Element Method Magnetics - a public domain code - was used to analyse the temperature rise of the form-wound stator windings of a 1250-kW induction motor. The thermal network was used in the thermal analysis of a 300-kW high-speed motor using form-wound stator windings. After the loss and thermal information have been collected, the losses in the stator form-wound windings of the induction motors are minimized in collaboration with temperature rise checking in the design stage. In addition, the loss and temperature rise analysis may offer numerical data to evaluate the possibility of using the form-wound windings for high-speed induction motors

Modelling Demagnetized Permanent Magnet Synchronous Generators using Permeance Network Model with Variable Flux Sources

Author's accepted manuscript© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.acceptedVersio

Detecting Eccentricity and Demagnetization Fault of Permanent Magnet Synchronous Generators in Transient State

Author's accepted manuscript© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.acceptedVersio