This paper addresses the diagnostics of inter-turn short-circuits in the stator windings of symmetrical six-phase induction motors supplied by an unbalanced voltage three-phase system. A new approach based on the analysis of the power zero-sequence component is proposed. Both simulation and experimental results are presented, that show the effectiveness of the proposed approach for discriminating between healthy and faulty motor operation, independently of the balanced/unbalanced nature of the supply voltage system.
This paper presents a comparison between two low voltage permanent magnet synchronous motors dedicated to an electric boat. One motor has a distributed winding and the other one an original concentrated winding developed in our laboratory. The originality of these two windings consists in the use of cylindrical solid bars. The AC additional losses due to the solid bars are considered. To compare the two windings, two prototypes were designed and manufactured. The both types of windings are presented and characterized with a developed test bench.
Eccentricity is a critical fault in permanent magnet (PM) machines. In this article, an eccentricity diagnosis method is proposed for dual three-phase PM (DTPPM) machines based on detecting the difference of zero-sequence voltage component (ZSVC) between two sets of three-phase windings. The research is carried out by finite-element method, and 10-pole/12-slot surface-mounted DTPPM machines with different winding configurations are modeled. Eccentricity significantly affects the ZSVC difference in DTPPM machines where a single set of three-phase windings is rotationally asymmetric. The fundamental component and fractional harmonics dominate in the ZSVC difference under static eccentricity (SE) and dynamic eccentricity (DE), respectively. Both the fault characteristic components appear under mixed eccentricity (ME). Moreover, the ZSVC in a single set of three-phase windings is analyzed for comparison. It shows that detecting ZSVC difference has better sensitivity to eccentricity. Furthermore, the effectiveness of the proposed method is verified under different load conditions and eccentricity conditions.
The transmission of a constant torque from zero to synchronous speed with low torque ripple via simple electromechanical devices is an important requirement for a wide range of industrial applications. Hysteresis couplers or clutches can be useful to improve the aforementioned performance indexes, thanks to their unique features. This paper analyzes the influence of the cost functions in the design optimization of magnetic hysteresis couplings. After a brief re-call of a fast method of analysis, several configurations are compared by optimizing the coupler geometry in order to maximize the average torque and minimize the amount of rare-earth material. The obtained results are then deeply analyzed allowing to draw general design guidelines with special emphasis on the influence of the number of poles, cost functions, outer envelope as well as the airgap thickness on the main performance indexes.
When the grid-side converter (GSC) is switched on, a large inrush current may occur if the synchronization between the grid and the GSC is not performed well. Hence, a grid voltage and GSC output voltage vectors must be synchronized before the GSC is switched on. This study proposes a novel sensorless synchronization method based on discontinuous currents induced by the grid voltage after applying a series of controlled short circuits to the GSC terminals. Grid voltage angle is estimated using sampled current, a discrete sliding mode observer, and a double generalized second-order integrator with frequency locked loop in both discontinuous and continuous mode. The proposed method ensures the proper synchronization and GSC operation in the continuous operating mode under load conditions. The effectiveness of the proposed method is verified by simulations in Plexim PLECS.
In this work, an updated methodology to determine the parameters of three-phase induction machines (IMs) is developed and presented. The goal of this determination is for a better representation of machines for the further applications of the parameter-based control system operated with different stator flux linkage levels, such as automotive applications. First, the theory of the T-form model (TFM) and the inverse Γ-form model (IGFM) are reviewed. The former review becomes the brick of the following interpretation of the developing methods for identifying these parameters. Moreover, a 2D electromagnetic finite element method (FEM) model of a 15kW IM is utilized to demonstrate the strength of the methodology on a real machine. Lastly, a comparison of results using the conventional test and the newly proposed method is presented, showing improvement.
Increasing the reliability of electric machines is paramount for various industrial applications. In particular, for advanced electric propulsion systems being developed for electric vehicles, aircraft, and ships, which incorporate high power and high torque density electric machines. Insulation failure is reported to be responsible for up to 66% of machine breakdowns and proves to be one of the most challenging areas to develop condition based monitoring methods. A major indicator of electrical insulation breakdown is the occurrence of partial discharge events. This paper presents a method for localising partial discharge emissions using acoustic sensor arrays and a cross-correlation based time-difference of arrival algorithm. The results from analytical experiments are reported for a large traction based switched reluctance machine which demonstrates the effectiveness of the approach with accuracy errors of less than 1 cm Euclidean distance. This work serves as a valuable precursor towards developing future experiments with hardware.
A co-simulation study of a wind-driven Doubly Fed Induction Generator and its connected power system is presented in this paper to study the generator performance under network disturbances. In order to accurately model core- saturation and harmonic effects, the machine is modelled using a Dynamic Phasor Finite Element model that couples the state variables of a co-simulated system. The system performance is simulated under three-phase short-circuit fault and a third- harmonic pollution in the machine’s feeding voltage. Simulation results of the Dynamic Phasor FEM method are compared to regular time-domain FEM (considering core saturation for both solvers) to prove the validity of the new method for modeling disturbed power systems in an accurate and fast way.
Kinematic chains have a variety of applications, taking a fundamental role in many industrial processes. Given the importance of kinematic chains, different techniques for monitoring and maintaining these devices have been documented over the last years. Among those, the analysis of infrared thermal images has proven to be a non-invasive and efficient method for the detection of multiple electromechanical faults. Virtual Reality (VR) is a recent technology that has not been used very often in industrial applications, nonetheless, VR can be an accessible and cheap way to assist in the training and capacitation process of industrial personal on specific engineering topics. This paper presents the design and development of a virtual environment for the detection of seven electromechanical faults in a kinematic chain. The designed VR tool is based on real thermographic data from experiments performed on a real kinematic chain where thermal images were acquired with a low-cost infrared sensor.
For high-speed permanent magnet machines (HSPMMs), the rotor retaining sleeve has a critical effect on thermal performances. This paper presents an analytical multi-element modelling method for predicting sleeve and magnet thermal fields for HSPMMs accounting for both metallic and non-metallic rotor sleeves. The proposed analytical multi-element thermal model consists of rotor sleeve and magnet, which are obtained based on the respective conduction heat equations in the axial centre domain. The proposed thermal model can be combined with a lumped-parameter thermal model considering the thermal states of the entire machine. Finally, based on a 3-slot/2-pole prototype HSPMM, the proposed analytical multi-element thermal model is validated by the finite element analysis.
This study presents a novel rotor structure for a magnet-assisted wound field motor. In the proposed motor, the field coil, bobbin, and pole piece are integrated to form field units, which are inserted into the rotor core from the axial direction. This structure allows reluctance torque, which is unavailable in conventional motors, to be utilized and exhibits improved torque density compared to that of conventional motors. Numerical verifications are conducted using the finite element method to validate the effectiveness of the proposed structure. Moreover, manufacturing tests are performed to verify the feasibility of the field-unit-type rotor. From the numerical results, it can be confirmed that the proposed structure achieves a magnet-assisted wound field motor with higher torque density than that of conventional motors.
In this study, we revisit the newly proposed high torque density double stator (DS) wound-field flux modulation machines (WF-FMMs) to highlight the important electromagnetic design performance concepts and provide parametric evaluation based on the ampere-turn excitation and armature windings. The topology of the DS machines to be considered is narrowed down to two variants of same stator types – the wound-field flux switching machine (WF-FSM) and the DC-excited Vernier reluctance machine (DC-VRM) – and both resized to ~1.5 kW to facilitate prototype fabrication and experimentation, for the first time. The preliminary performance and ampere-turn parametric evaluation based on similar design constraints and undertaken in finite element analyses (FEA), show the DS WF-FSM exceeding its counterpart in terms of torque capability and efficiency, while producing both sinusoidal and symmetric phase quantities. On that basis, the DS WF-FSM is primed for experimentation, and it is currently under construction.
This paper provides a comparison on the difference of hairpin winding and pull-in winding technology on the ac copper losses of permanent magnet (PM) excited electrical machines. Finite Element Analysis (FEA) is used to study the current displacement effects under pure sinusoidal current and pulse width modulated (PWM) voltage supply. The resulting additional ac copper losses are analyzed for both winding technologies.
This work focuses on the evaluation of the calibration strategy of the CPB06 asymmetry parameter k and its influence on the predictive behavior of the model at large deformations for Ti64. The direct identification strategy is based on fitting the model with experimental strain hardening data up to the onset of plastic instability. The inverse strategy is performed by reducing the prediction errors of the load–displacement curves of both the cylindrical bar tensile test and the elliptical cylinder compression test. Both strategies use an orthotropic tensor of the CPB06 criterion previously identified from experiments performed in all three dimensions. The results presented quantify the maximum error achieved by each method in terms of elongation and load predictions for specimens with different stress states.
The lubricant behaviour at elevated temperatures was investigated by conducting pin-on-disc tests between P20 tool steel and AA7075 aluminium alloy. The evolutions of coefficient of friction (COF) at elevated temperatures showed three distinct stages: stage I (low friction stage), in which boundary lubrication was prevalent and the coefficient of friction was low; stage II (transient stage), in which the lubricant film thickness decreased to a critical value and the coefficient of friction increased rapidly; and stage III (breakdown stage), in which the lubricant was completely removed from the interface and the coefficient of friction was equal to its value under dry sliding conditions. In the present work, 2 types of water-graphite based lubricants were studied by pin-on-disc tests under different contact conditions. The effects of tooling and workpiece temperature determined from the experimental results were investigated in this paper and a comparison with an oil-graphite based lubricant was conducted.
This study presents an experimental protocol for the characterization of the strain rate effects on the nonlinear behavior of an organic matrix composite. This protocol is based on the development of a displacement interrupted tensile test device adapted to servo-hydraulic jacks. The protocol allows for the performance of incremental cyclic tests for intermediate dynamic loading rates thanks to the device. Such combination allows for the evaluation of the macroscopic damage variable, the irreversible strain and the reversible phase after nonlinear loading. It also allows for the analysis of damage mechanisms such as cracks and delamination after cyclic dynamic loadings.
The effect of filler content on viscoelastic properties of carbon black filled vulcanized natural rubber is here studied. The filled natural rubber specimens are subjected to dynamic mechanical loading with the temperature varying from −80 °C to 100 °C. While the storage modulus of unfilled and filled rubber materials remains nearly the same in the glassy state, the glass transition temperature significantly increased in the case of latter. The data also indicate that the rubbery modulus of filled rubber increases with increasing carbon black content. The loss factor data suggest that the damping characteristics of filled rubber decrease with increasing carbon black content.
Steel components in the boilers of nuclear reactors are subject to high temperatures and varying loading conditions. This can introduce time-dependent and time-independent plasticity, which can interact with one another. Specimens of 316H austenitic stainless steel were heated to 550 °C and tensile pre-strained to 8%, 11% and 14% followed by 200 h, 280 MPa creep tests. These tests showed an increase in creep resistance with increasing tensile pre-strain. Macroscale simulations using RCC-MR deformation laws proved ineffective at predicting this interaction. Microscale crystal plasticity simulations proved effective at predicting the trends observed experimentally, hence demonstrating the potential of crystal plasticity as a predictive tool for structural integrity analysis.
In the rotating armature permanent magnet motor (RAPMM), the movement of the rotor slot in relation to the stator results in variations in the electromagnetic excitation force and slot-frequency vibration. To diminish the slot-frequency vibration of RAPMM, a novel slotless rotating armature permanent magnet motor (SRAPMM) is proposed and prototype-tested. The finite element method is used to simulate the magnetic field, torque, and torque ripple, revealing that the air gap flux density and radial force remain relatively constant. Vibration experiments were conducted on two SRAPMMs having different magnetic pole widths. The results indicate that the main vibration frequency is an even multiple of the current frequency when the motor is unloaded. After loading the motor, the amplitude of the electromagnetic vibration is significantly smaller than that caused by mechanical factors, suggesting that the SRAPMM is a reliable option when strict vibration requirements are applied.
