In this paper a surface inspection system for rails is proposed. There is a lack of commercial systems and publications about surface inspection of rails. Therefore, the quality control developed by rail manufacturers depends on their own developed systems or on the equipments provided by very few sellers. Commercial systems must be configured manually by experts of seller companies. The configuration process requires large sets of all types of manufactured rails along several periods of time and the active participation of the quality engineers of the manufacturer. This is a long, cumbersome and very expensive process. In this paper we propose a new system that can be configured using a systematic method that can be performed by the quality engineers of the manufacturer. The proposed inspection system uses differential images of the rail surfaces obtained with a technique called the Spectral Images Differentiation Procedure. These images are processed using a computer vision algorithm that looks for variations in the pixel values among the images. In order to offer more information, a neural network approach is used for classifying detected defects into six types. The proposed system is an open solution for the inspection of rail surface, easy to implement at an affordable cost, which can be systematically configured by the quality engineers of the manufacturing company.
This paper intends to compare the many different solutions available to design a busbar interconnection. Starting from a single copper plate and going to multilayer busbars, the influence of the external shape of the sheet, of the number and the nature of holes and apertures are considered. Simulations and measurements are used to determine the stray inductance of the different busbars. Design rules are deduced from the many case studies, based on industrial examples
New application areas are demanding the development of ultra-high speed electrical machines. Significant challenges exist to produce a test bench that is capable of withstanding operating speeds exceeding 500,000 rpm and measuring very low torque values of mNm. This paper describes a purpose built test bench that is able to characterize the operation of an ultra-high speed drive system. Furthermore, the calculation of electromagnetic losses, air friction and critical speeds is presented and a comparison of analytical and experimental results is given. The ultra-high speed machine has an efficiency of 95%, however, in the upper speed ranges the frictional losses become dominant
This paper presents the analysis, design, and experimentation of a closed-loop metal halide (MH) lamp ballast, which supplies the lamp with a low-frequency square waveform. First, a discussion related to the lamp parameter that should be regulated (power or current) is presented, since this issue has not been well addressed in the previous literature. Experiments demonstrated that lamp current can be chosen to be kept constant during lamp life, because it can attenuate the effect of lumen depreciation with lamp ageing, and, on the other hand, the lamp power does not reach overrated values during lamp life. Second, in order to analyze the open-loop characteristic and design a suitable controller for the closed-loop operation, a dynamic model of the lamp-ballast system is developed. Therefore, a phase-lag controller is proposed to minimize the steady-state error and provide a phase margin of about 80. (fully stable system). Experimental results using a flyback-based ballast supplying 35-W MH lamps with 100, 2500, and 5000 burning hours are presented to validate the theoretical analysis. It is demonstrated that the lamp current is kept constant at rated value (0.42 A) within the entire input voltage range. The time response of the complete closed-loop system is about 5 ms.
In this paper a new topology for contactless energy transfer is proposed and tested that can transfer energy to a moving actuator using inductive coupling. The proposed topology provides long-stroke contactless energy transfer capability in a plane and a short-stroke movement of a few millimeters perpendicular to the plane. In addition, it is tolerant to small rotations. The experimental setup consists of a platform with one secondary coil, which is attached to a linear actuator and a 3-phase brushless electromotor. Underneath the platform is an array of primary coils, which are each connected to a half-bridge square wave power supply. The energy transfer to the electromotor is measured while the platform is moved over the array of primary coils by the linear actuator. The secondary coil moves with a stroke of 18 cm at speeds over 1 m/s, while up to 33 W power is transferred with 90% efficiency
The transient protection with fault generated high frequency transient signals is a developmental direction of modern power system. It has the advantages: quick fault detection, high precision, no influence by the foundation frequency signal, current transformer saturation and fault resistance. Whereas, the protection is still not applied widely in power systems because the theories about the high frequency transient signal transmission and declining are not very clear. In order to improve it, the frequency impedance characteristics of transmission line are analyzed in the paper. And their effects in the transient protection, especially in traveling wave based fault location are presented. Wavelet packet analysis is then introduced to decompose the fault produced transient signals and remove disturbances, and the wavelet packed analysis based transient protection is simulated. The precision of protection and fault location can be improved
Output limits of the power system stabilizer (PSS) can improve the system damping performance immediately following a large disturbance. Due to nonsmooth nonlinearities arising from the saturation limits, these values cannot be determined by the conventional tuning methods based on linear analysis. Only ad hoc tuning procedures can been used. A feedforward neural network (with a structure of multilayer perceptron neural network) is applied to identify the dynamics of an objective function formed by the states and, thereafter, to compute the gradients required in the nonlinear parameter optimization. Moreover, its derivative information is used to replace that obtained from the trajectory sensitivities based on the hybrid system model with the differential-algebraic-impulsive-switched structure. The optimal output limits of the PSS tuned by the proposed method are evaluated by time-domain simulation in both a single-machine infinite bus system and a multimachine power system.
The purpose of this work is to provide validated models to estimate the performance of a SiC-based converter as a utility interface in battery systems. System design and modeling are described in detail. Simulations are done for both a SiC JFET converter and its Si counterpart based on the quality of tested devices. The simulation results indicate that in both charging and discharging modes, the SiC converter has a better performance compared to the Si one. (1) With the same heatsink size and ambient temperature, great advantages in efficiency and junction temperatures were found in the SiC-based converter. (2) With the same thermal limit, large savings in system weight and volume combined with a high efficiency were found in the SiC-based converter
A three-phase induction motor model which represents the motor behavior over a wide range of frequencies from 10 Hz - 10 MHz is presented in this paper. The model is universal in the sense that common mode, differential mode and bearing circuit models are combined into one three-phase equivalent circuit model. The proposed model is basically an extension of the low frequency IEEE Standard 112 circuit model. The proposed model was simulated and verified experimentally with results presented.
This paper presents a new adaptive flux observer with a constant gain for speed identification. The theory of Lyapunov stability is used to design adaptive flux observer and speed estimator. The stability of flux observer is gauranteed by a linear matrix inequality (LMI), and the constant observer gain is obtained by solving the LMI with LMI toolbox in MATLAB. The problem of unstable region which arises from using pole-placement technique is overcome. Based on the proposed flux observer, the adaptive laws for estimation speed is given. Finally, a sensorless induction motor drive is designed by using the speed adaptive estimation scheme and the direct torque control technique for torque and stator flux control. The speed sensor-less direct torque control IM drive system is capable of working from very low speed to high speed and exhibits good dynamic and steady-state performance. The steady-state and dynamic performance of the proposed sensorless drive are demonstrated using simulation and experimental results
This paper proposes an on-line compensation strategy of the unwanted disturbance voltage due to the zero current clamping effect for high-frequency-signal-injection based sensorless control schemes. An analytical model is derived which reveals intrinsic characteristics of the zero clamping effect for the high frequency signal injection. The model in this form is subsequently incorporated into the development of a specialized off-line commissioning test to find motor inductances and a voltage distortion factor. From the sensitivity analysis of the effect on the magnetic saturation, it is confirmed that the compensation error due to saturation has little negative impact on the proposed compensation method. The compensation result leads to an accurate position estimate during zero-current clamping region and the proposed scheme does not rely on a complicated look-up table. Experiments demonstrate the superiority of the proposed method in suppressing the voltage distortions caused by the zero-current clamping effect
This paper deals with the endwinding cooling problems of totally enclosed fan-cooled (TEFC) induction motors. In order to obtain information about the phenomena involved in the motor end space, three "ad hoc" prototypes have been built. The complete test-bench setup, together with the followed test procedures, is reported in detail. The measurement results have shown that all the motor-part overtemperatures (winding, endwindings, stator lamination, and external motor frame) decreasing, with the inner air speed increasing. The measured motor overtemperatures and losses allow the thermal-resistance identification of a simplified thermal model suitable to describe the thermal behaviors of the prototypes. By the endwinding-to-motor frame thermal resistance, the related heat-exchange coefficients have been evaluated as a function of the rotor speed. The proposed procedure allows separating the forced-convection contribution by the other thermal-exchange phenomena that occur in the end-space regions. The obtained heat-transfer coefficients are in agreement with the results reported in the past literature.
The interiors of electrical conduits located on rooftops in full sunlight become considerably hotter than those located in shaded areas. Differentials between these conduit interior temperatures and outside air temperatures (the latter always measured in the shade) can easily reach 39degC (70degF) for conduits lying directly on a dark roof. As the height of the conduit above the roof increases, this temperature differential decreases, to perhaps 15degC (27degF) at a height of 0.9 m (36 in) above the roof. Lighter-colored roofs, although they keep the interior of the buildings cooler, actually reflect more heat onto conduits located more than a few centimeters above the roof. This makes these conduit interiors hotter as compared to conduits located above dark-colored roofs. In practice, the actual temperatures inside conduits are seldom taken into account when electrical ampacity calculations are made. This can lead to serious overheating and even failure of electrical cables inside the conduits.
Two new models for specific power losses in cold rolled motor lamination steel are described together with procedures for coefficient identification from standard multi-frequency Epstein or single sheet tests. The eddy current and hysteresis loss coefficients of the improved models are dependent of induction (flux density) and/or frequency and the errors are substantially lower than those of conventional models over a very wide range of sinusoidal excitation, from 20Hz to 2kHz and 0.05T up to 2T. The model that considers the coefficients to be variable, with the exception of the hysteresis loss power coefficient that has a constant value of 2, is superior in terms of applicability and physical interpretation. Also included are a comparative study of the material models on three samples of typical steel, mathematical formulations for the extension from the frequency to the time domain and examples of validation from electrical machines studies.
In this paper, static and switching characteristics of a 1200V 4H-SiC BJT at bus voltage of 600V are reported for the first time. Comparison was made between 1200V SiC BJT and 1200V Si IGBT. The experimental data show the SiC BJT have much smaller conduction and switching losses than the Si IGBT. Our previous work showed a large RBSOA of SiC BJT. No second breakdown, which is the most unattractive aspect of the Si BJT, was observed in the 1200V SiC BJT. The results prove that, unlike Si BJTs, BJTs in 4H-SiC are good competitors to Si IGBTs
Further improvements in the efficiency of compact fluorescent lamps can be achieved by optimizing the magnetic components in the electronic ballast. Resonant inductors were evaluated in several commercial integrally ballasted lamps. Winding optimization programs were used to redesign the windings of an example inductor. Two of the proposed winding designs were built and confirmed to provide reductions in winding loss of over 40%
This paper gives an overview on the SOA of high power semiconductors. Two main types of high power semiconductors are investigated: large area devices and modules with paralleled chips. The paper explains the limits of SOA and ways of improving it in the semiconductor design level, as well as it gives practical advantages for a high SOA in the device
In this paper, an alternative on-line drawing force and torque estimation method for use in wire drawing processes is presented. The method considered here is based on a simple Luenberguer observer and uses only measured variables available from a motor drive system such as terminal voltages and currents and rotor velocity. The proposed algorithm permits to implement functions such as condition monitoring of die wear, workpiece fracture and lubricant analysis. The performance and some practical implementation features of the load torque estimator are analyzed. Theoretical development and simulation results are presented to support the use of such method on load torque and drawing force estimation.
