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Influence of leading ultrasonic vibrations on the process forces in the friction stir lap welding of AA 6061-T6 with and without ultrasonic vibrations is investigated at varied welding speeds. The axial force, traverse force, and tool torque in the processes are determined by adopting a recently developed method that uses electrical signals of the servo motors and main spindle AC motor of the friction stir welding machine during the welding process. It is found that the exerted ultrasonic vibrations decrease the welding forces without compromising the mechanical properties of welds. The effect of ultrasonic vibrations on traverse force is more pronounced than that on the tool torque and axial force. Force measurements at different welding speeds indicated that the axial force and traverse force varied significantly with travel speed of tool. Not much difference is found in the tool torque variation. With ultrasonic vibrations, the reduction in welding force in different directions is affected differently by welding speed. The ultrasonic effect on welding forces is found to be governed by the travel speeds of both the tool and workpiece. [ABSTRACT FROM AUTHOR]

In ac motor drives, the fixed-frequency harmonic components of output voltage and current from the inverter with fixed-frequency pulsewidth modulation usually lead to electromagnetic interference (EMI). The spread spectrum clock generation (SSCG) is a widely used solution for this problem. Adjusting the switching frequency to reduce EMI is one kind of practicable scheme among SSCG methods. How to design an optimal or suitable modulation profile is a research emphasis of scholars and has been discussed in depth in many literatures. However, apart from the modulation profile, the mode and quality of carrier are also important and can be improved. In most frequency modulation methods, due to the limitation of the conventional carrier generation mode, the implementation of the new frequency instruction has to wait for the termination of the last switching period. In order to eliminate the waiting state and design a simpler algorithm, this paper has proposed a wait-free phase-continuous carrier frequency modulation (WPCFM) strategy by combining the direct digital frequency synthesizer theory and proper temporal planning of control interruptions. Besides, a theoretical analysis of WPCFM, including quantization error, frequency jitter, phase delay, and voltage distortion, has been finished. Moreover, compared with conventional methods, a more convenient, feasible, and simpler field-programmable gate array based algorithm implementation method and the control structure of WPCFM are also introduced. The analysis shows that, although WPCFM causes a slight increase of the current ripple, it can solve the partial frequency nonuniform distribution problem of the conventional method, and it has a potential value of applications in the wide band gap motor drive systems. The effectiveness of the WPCFM is verified by several sets of EMI reduction experiments where classical periodic carrier frequency modulations are applied. [ABSTRACT FROM AUTHOR]

Of late, most types of ac motors can be operated using variable frequency drives (VFDs) by merely selecting the type of motor and the corresponding control method using a sophisticated all-in-one software platform. As technology improves, the VFD is becoming more of a plug and play, software-based electrical equipment. There have been no comparable technological advancement/improvements in the hardware realm except for the potential use of wide band gap devices (SiC or GaN) to reduce losses. The idea being proposed here is a hardware platform that is similar to an all-in-one software platform. By reconfiguring the hardware platform, one could achieve totally new or additional features that can enhance the overall performance of a VFD. It is shown that by adding one small hardware device as part of the main VFD, the unit can be reconfigured to provide four distinct features/functions as desired. An off-the-shelf VFD is used as an example to illustrate the various configurations achievable based on the proposed hardware modification. The proposed topology's cost, size, and features are compared with a traditional VFD with externally added components to achieve similar features/functions. In addition, the amount of time estimated to be saved in developing the proposed four-in-one converter compared to developing individual, external units to achieve similar features and functions is also investigated. [ABSTRACT FROM AUTHOR]

The control of a tri-axis computerized numerical control machine tool platform, which is driven by an AC servo motor is discussed in this paper. To establish a system model, the particle swarm optimization algorithm was used to transform the X–Y platform of a machine tool into a transfer function before simulation and verification of digital control was done using MATLAB. The control methods used in this study include proportional-integral-derivative control, quantitative feedback design theory and sliding mode control. They were realized with C# and the errors of motion trajectories generated by the controllers were observed. It was concluded that of the three methods studied, sliding mode control produced the lowest error rate. [ABSTRACT FROM AUTHOR]

Irrigated agriculture is extremely important for Brazil and this technology has increasingly spread among small producers in the country. Irrigation systems located in olive groves add high rates of productivity to plants, especially hardwood vegetables. However, it is necessary to invest in sustainable technologies which reduce energy costs in localized irrigation. Therefore, the objective of this work was to evaluate the technical and economic viability of photovoltaic energy through simulating a drip irrigation system for lettuce crops. Tests were carried out on a hydraulic bench with drip irrigation simulations and set performance curves of the set were compared with the energy from the conventional system (electric grid) and photovoltaic energy. To do so, a direct current electric motor pump and an alternating current electric motor pump were used. The results showed that the use of irrigation for the lettuce crop promoted by photovoltaic energy reduced energy costs by 83.80% when compared to conventional energy. [ABSTRACT FROM AUTHOR]

With the increasing proliferation of variable speed drive, the demand for the more reliable drive is also on the rise. Despite the growing interest on more advanced motors like permanent magnet and flux switching motors, three-phase induction motors (3ph-IMs) are still the main workhorse in the industry and hence the fault-tolerant control of these motor drives remains an interesting and important topic. In this paper, a simple fault-tolerant field-oriented control technique for 3ph-IMs is presented. It is shown that by injecting zero-sequence compensation voltage in a feedforward manner, open-circuit faults can be effectively tolerated. Compared to the previous feedforward fault-tolerant control methods, the proposed approach does not require the knowledge of the magnetizing inductance, which is tricky to be obtained in induction motors. Furthermore, the unified feedforward approach allows the same control structure to be used for different fault-tolerant 3ph-IMs drive topologies, with minor modifications to the feedforward terms. In addition, the effect of inverter non-idealities on the performance of the proposed control method is also highlighted and addressed. The effectiveness of the proposed controller is verified using MATLAB simulation and further validated using experimental tests. This paper is accompanied by a video demonstrating the experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a power controller used for three-phase inverters with small dc-link capacitors fed by a single-phase diode rectifier. The effect of the reactive power was investigated based on a power flow analysis between a dc-link and three-phase inverter. These results enable the development of a direct active/reactive power controller in discrete time instead of adopting a classical proportional-integral (PI)-type current regulator, which directly leverages the total power flow of the system. A suitable reactive power selection method was presented to improve the overall system efficiency. The command voltage vector at each discrete time step can be simply and intuitively determined by an inverter power without requiring motor current-regulating PI gains and additional control functions. The proposed controller regulates an average motor velocity/airgap torque while simultaneously shaping a grid-side current with a high power factor and low harmonics to meet IEC61000-3-2 requirements. The proposed structure can be applied to three-phase inverters for a broad family of ac motors, such as induction and permanent magnet synchronous motors. [ABSTRACT FROM AUTHOR]

Integral-slot electrical machines require modifications and optimization of both stator and rotor to maximize the machine performance. In addition, sub-harmonics in magneto-motive force distributions is an important issue in motors with fractional-slot concentrated windings. These additional sub- and super-harmonics increase iron losses, which becomes an even bigger challenge in high speed/frequency applications. A permanent-magnet (PM) motor with unbalanced winding (UBW) and unconventional slot numbers is a good option for applications that require smooth torque output and low back electromotive force voltage harmonics. In this paper, different winding configurations and displacements of an unconventional nine-phase PM motor with both balanced fractional-slot winding and UBW structures have been investigated. The focus has been on 117-slot with 12-pole (for the balanced winding motor) and 36-pole (for the UBW motor) combinations. Motor prototypes with UBW configurations have been manufactured. The finite-element analyses results have been validated with experimental results and it is shown that such unconventional slot/pole combinations can be a good option for some high-power applications. [ABSTRACT FROM AUTHOR]

SiC mosfets allow a higher frequency, lighter weight inverter over their Si counterparts for electric vehicle (EV) applications. However, using SiC-based EV traction inverters is likely to increase the shaft voltage in an ac motor drive system, which significantly affects the reliability of the system. This paper investigates the impact of high-speed switching of SiC devices and high switching frequency of SiC-based inverter on the common-mode voltage (CMV) and the shaft voltage. It is theoretically illustrated and experimentally demonstrated that the high switching frequency increases the amplitude of the shaft voltage, while the fast switching speed has limited influence on both CMV and the shaft voltage. Afterward, active zero state pulsewidth modulation (AZSPWM) and common-mode chokes are employed to mitigate the shaft voltage. The experimental results show that either the AZSPWM modulation scheme or common-mode chokes have the capability to minimize the shaft voltage. Better performance can be achieved by utilizing both techniques simultaneously. It is also observed that the high switching frequency enabled by the fast-speed SiC device is able to be helpful to the use of reduced shaft voltage technologies. [ABSTRACT FROM AUTHOR]

This paper deals with data-driven fault diagnosis of three-phase induction motor. The tools from subspace identification based data-driven scheme are utilized to design a framework of fault detection and isolation. The fault detection scheme is so designed that it caters for even small magnitude faults. In order to discriminate different faults, a fault isolation algorithm is proposed. Isolation thresholds are designed. The results show the effectiveness of the proposed schemes. [ABSTRACT FROM AUTHOR]

A permanent magnet synchronous motor (PMSM) drive based on a novel four-switch inverter is investigated in this work. No dead-time insertion/compensation is needed for the inverter because its upper and lower power devices will not shoot through. Two space vector pulsewidth modulation approaches for the four-switch inverter are developed that enable the suppression of the zero sequence voltage/current. Finally, simulation and experimental results verify that the PMSM can be effectively controlled with the novel four-switch inverter, and the system has good dynamic and static performance. The proposed approach provides a feasible alternative for low-cost motor drives. [ABSTRACT FROM AUTHOR]

This paper discusses the optimization of surface-mounted permanent magnet brushless AC (PMBLAC) motor using Analytical Sub-domain model with Differential Evolution Algorithm (ASDEA). Only two regions were considered in this analytical sub-domain model, ie magnet and airgap regions, with assistance of Complex Relative Permeance Function (CRPF) to account for the stator slotting effect. Five machine parameters were chosen to be optimized, namely the magnet arc-pole-pitch ratio, slot opening width, magnet thickness, airgap length and stator inner radius. The optimization process has four objectives, ie minimum torque ripple, low cogging torque, high efficiency, and high output torque. The results from the optimized ASDEA were compared with the Analytical Sub-domain Genetic Algorithm (ASGA) and further validated against 2-D finite element model (FEM). Results show a good agreement between analytically optimized models and finite element model. The ASDEA has faster computational time compared to ASGA, and this provides benefit in terms of reducing the machine design parameterization time and less redundancy work required to achieve motor design specifications. [ABSTRACT FROM AUTHOR]

As a new type of global energy-saving transmission mode, frequency conversion hydraulic drive system has been widely used. Since hydraulic systems become more complex and transfer more power, operating accidents often occur unexpectedly. Therefore, online monitoring of the running state of the hydraulic system is significant during its long-term operation. The pressure, flow, and vibration signals obtained by traditional monitoring methods are nonstationary and susceptible to disturbance. In order to solve this problem, a method of monitoring power condition of the motor driven hydraulic system based on input voltage and current of the motor is proposed. The present study uses the amplitude and phase information of the voltage and current signals on the stator side of the AC motor to form a dynamic power circle graph and extracts feature information from the graph to monitor the power state and its dynamic change process of the hydraulic system. Results obtained from experiments conducted under different frequencies and loads indicate that the proposed method can realize the online monitoring successfully and effectively. Furthermore, the method has another advantage of monitoring the dynamic power change process of the hydraulic drive system and the power matching process between the motor and the system load condition in a visualized way. [ABSTRACT FROM AUTHOR]

In this study, a constant frequency control technique is proposed for improving the overall power efficiency of a squirrel-cage AC induction motor, so that the induction motor can maintain its original operating state under low energy consumption. In this study, a semiconductor component, the Silicon Controlled Rectifier (SCR), was used as the component for adjusting the voltage phase trigger, and a constant frequency control module was developed to trigger the SCR through the output signals. The experiment records the energy consumption of the rated voltage operation of 0.47 kWh in 4 cycles, and the energy consumption of the voltage adjusting operation is 0.402 kWh. The calculated energy saving rate is about 12%. In addition, the power factor (PF) of the tested induction motor was increased from 0.44 to 0.53 at a low load, which is increased by 22.1%, while the PF of the overall low and high load is increased by about 12.9%. This study improves the conversion effect of converting the overall apparent power (kVA) to active power, to verify the energy-saving effect on the modulation of the voltage input of the squirrel-cage AC induction motor. • This study presents a constant speed control technology. • A silicon controlled rectifier (SCR) element was used to modulate the phase angle. • The proposed control theory effectively reduced unnecessary waste of power energy. • The proposed technology effectively reduced overall energy consumption by 12%. [ABSTRACT FROM AUTHOR]

With the increasing demand for electric vehicles, reliability in motor drives is an issue of growing importance. Over the years, various fault-tolerant three-phase motor drive topologies have been introduced and their performances have been investigated. Evaluation of the postfault power of a fault-tolerant drive should take into account both the postfault torque and speed, which depend on both the postfault current and voltage limits. Nevertheless, the postfault motor voltage limits are usually omitted from discussion. Furthermore, current limit in induction motor drive is not as direct as that in permanent magnet motor drive, due to the presence of the flux current. In this paper, the performances of available fault-tolerant three-phase induction motor drives have been reinvestigated, taking into account the impact of not just currents, but also voltage limits for both the inverter and machine. By deriving the postfault machine voltage equations, the effects of machine parameters and operating point on the voltage limit and hence the speed limit are explained. Depending on the topology, the motor may be able to run above the rated speed to gain extra power. The analysis is verified through experiment results on a 1 kW induction machine for four different fault-tolerant drive topologies. [ABSTRACT FROM AUTHOR]

In high-performance control of ac machines through variable frequency drives, the knowledge of machine parameters plays a decisive role. The accuracy with which machine parameters can be known is directly related to the time and effort put during the testing and commissioning process. In the ever-demanding industrial environments, the time spent on parameter identification translates into loss of production. To reduce commissioning times, research in this direction has focused on automatizing the identification procedure without loss of accuracy. This paper reviews different lines of research adopted over the past few decades for machine parameter identification. Parameter estimation of ac machines is considered because of their widespread applications from servomechanisms to traction to aviation. The surveyed works include self-commissioning schemes that have become an integral part and a salient feature of modern electric drives. This feature enables the drives to automatically identify machine parameters and tune the control loops. [ABSTRACT FROM AUTHOR]

The thermal environment inside a broiler house has a great influence on animal welfare and productivity during the production phase. Among the importance of the chicken litter is the function of absorbing moisture, provide thermal insulation and provide a soft surface for broilers. The skin temperature is an important physiological parameter to quantify the thermal comfort of animals, its variations may occur as a function of thermal variables. So, the aim of this work was to analyse the magnitude and spatial variability of chicken litter temperature and relative humidity of the air and to correlate them with the spatial distribution of chicks' skin surface temperature throughout the broiler house during the 7th, 14th and 21st days of the chicks' life, using geostatistical techniques. The experiment was performed in a commercial broiler house located in the western mesoregion of Minas Gerais, Brazil, where 28,000 male Cobb chicks were housed. The heating system consisted of an industrial indirect-fired biomass furnace. The heated air was inflated by an AC motor, 2,206 W of power, 1,725 RPM. Geostatistical techniques were used through semivariogram analysis and isochore maps were generated through data interpolation by kriging. The semivariogram was fitted by the restricted maximum likelihood method. The used mathematical model was the spherical one. After fitting the semivariograms, the data were interpolated by ordinary kriging. The semivariograms along with the isochore maps allowed identifying the non-uniformity of spatial distribution of the broiler litter temperature throughout the broiler house for 3 days of chicks' life. It was observed that skin surface presented a positive correlation with the litter temperature and a negative correlation with the air humidity. The semivariograms along with the isochore maps allowed identifying the non-uniformity of spatial distribution of the litter temperature, air humidity and skin temperature of chicks throughout the broiler aviary for the three days. In addition, the use of geostatistics and distribution maps made possible to identify different environmental conditions in regions inside the broiler house that may harm the development of chicks. [ABSTRACT FROM AUTHOR]

With the development of renewable energy, grid-connected inverter technology has become an important research area. When compared with traditional silicon IGBT power devices, the silicon carbide (SiC) MOSFET shows obvious advantages in terms of its high-power density, low power loss and high-efficiency power supply system. It is suggested that this technology is highly suitable for three-phase AC motors, renewable energy vehicles, aerospace and military power supplies, etc. This paper focuses on the SiC MOSFET behaviors that concern the parasitic component influence throughout the whole working process, which is based on a three-phase grid-connected inverter. A high-speed model of power switch devices is built and theoretically analyzed. Then the power loss is determined through experimental validation. [ABSTRACT FROM AUTHOR]

In this survey paper, resonant and quasiresonant DC link inverters are reexamined for AC motor drive applications. Critical evaluation of representative topologies is based on simulation and waveform analysis to characterize current/voltage stress of components, control timing constraints and feasibility. A special concern over inverter common-mode voltage and voltage gradient du/dt limitation capacity is discussed for motor bearing and winding insulation safety. Experimental records of the laboratory developed parallel quasiresonant DC link inverter feeding induction motor confirm results of analysis. Comparative tables and simulation results demonstrate characteristic features of various schemes. [ABSTRACT FROM AUTHOR]

A dimensionality reduction load torque observed is designed to provide compensation control for the motor with the observation value of load torque converted over for the problem that load disturbance decreases the control precision of servo system. A three-loop mathematical model is established for the servo control system. Use of two-/three-order optimal model theory contributed to the derivation of the tuning formula for three-loop control parameters. A simulation model is established for the space vector control of AC servo system. The simulation experiment validates that the tuned three-loop parameter provides the system with good dynamic performance. An experiment platform is built. The load sudden change experiment of the motor demonstrates the feasibility that torque compensation control improves the control precision of servo system in the presence of load disturbance. [ABSTRACT FROM AUTHOR]

This article studies the efficacy of a time-scale technique based on DWT for both stator and rotor asymmetries faults detection in WRIMs. The preliminary effort on the RAF detection in IMs relied mainly on the energy evaluation of a known low frequency bandwidth through DWT analysis. It was illustrated that the SCSVM and the IMSC are both good indicators for the RAF monitoring in steady state working conditions of WRIMs. In this work, it will be shown that in the case of any load variation, there is a time-varying DC component that may affect the energy evaluation criterion, resulting in a false alarm. Thus, an efficient method is proposed to estimate and then, to remove this DC component from both SCSVM and IMSC, before the energy evaluation through DWT analysis. Furthermore, by introducing a new frequency bandwidth, associated with SAF in the rotor current signature, this method can be extended to a universal slip independent stator and rotor asymmetries faults detection technique in WRIMs. The proposed approach is validated by experimental tests using a 7.5kW WRIM test rig. [ABSTRACT FROM AUTHOR]

Although colossal magnetoresistance (MR) with direct- or low-frequency currents ($f < 1$ KHz) in polycrystalline La0.7Sr0.3MnO3 sample has been extensively reported in the literature, magneto-transport in megahertz to gigahertz range is seldom studied. Here, we report the magnetic field dependence of ac resistance (${R}$) and reactance (${X}$) of polycrystalline La0.7Sr0.3MnO3 sample carrying high-frequency current ($f = 1$ MHz–3 GHz) in axial dc magnetic fields ($- 1\,\,\text {kOe} < H< 1\ \text{kOe}$) at 300 K. While R(H) shows a single peak centered around $H = 0$ for $1 \le f \le 30$ MHz, the peak transforms into a dip at $H = 0$ accompanied by double peaks at $H = \pm H_{P}$ for higher frequencies. The position of the double peaks shifts to higher magnetic fields with increasing frequency. Alternating current MR at 1 kOe increases from −0.7% for $f = 1$ MHz, −20% for $f = 50$ MHz, and +28% for 3 GHz at $H_{p}$. The transition from the single to double peak behavior is also seen in ${X}$ (${H}$) with additional features near-zero field for $f \ge 2$ GHz. While the enhanced value of the negative MR is attributed to the increase in magnetic skin depth due to the suppression of transverse permeability, the positive MR is attributed to the contribution from induced strong transverse permeability and ferromagnetic resonance. [ABSTRACT FROM AUTHOR]

This paper offers methods to analyze the performance of three-phase synchronous machines operating with an unsymmetrical stator winding caused by cutting out and bypassing coils. The resulting unsymmetrical current distribution in the stator winding tends to produce overheating in parts of the stator and damper windings at full load as well as torque pulsations. Thus, the main objective of this study is to determine the maximal load, under which the unsymmetrical machine may operate without exceeding the permissible temperature limit. Based on the multiloop method, a mathematical model of a synchronous machine with missing coils in the stator winding is developed. In order to determine the current distribution, the machines’ system of differential equations is solved by using a numerical integration method (Runge–Kutta method). As an alternative method, the system of differential equations in the steady state is reduced to a system of algebraic equations, which can be solved with the Gaussian elimination method. Both methods are validated by the measurement results of a 25-kW salient pole synchronous machine. Furthermore, both the circulating current within the parallel branches and the line currents of the different phases as a result of coil or coil group cut-outs are analyzed for a large 41-MW cylindrical rotor synchronous motor. [ABSTRACT FROM AUTHOR]

This paper proposes the novel scalable saturated model of synchronous permanent magnet machines, which combines ultrafast scaling laws with a saturated flux-linkage and loss model. The scalable model is used for the fast and accurate calculation of efficiency/loss maps and can also be used for drive cycle analysis including the calculation of energy consumption. It is verified by comparison with an existing state-of-the-art efficiency map and drive cycle analysis software. Additionally, an experimental verification of a saturated flux-linkage and loss model is presented. The additional possible usage of the scalable model is to find the optimal size of a scaled machine in order to meet the drive cycle performance and requirements of a traction motor. [ABSTRACT FROM AUTHOR]

In this paper, the influence of saturation and cross-coupling effects on the copper loss minimization for synchronous machines with strong saliencies, especially the permanent-magnet-assisted synchronous reluctance machines and reluctance synchronous machines are analyzed. It is shown that state-of-the-art methods for saturation consideration through the absolute inductances fail for these machines. A novel method for maximum torque per ampere estimation, which includes the consideration of these effects through the use of differential inductances, is proposed and its effectiveness is shown through finite-element analysis and experiments. [ABSTRACT FROM AUTHOR]

In this paper, an improved predictive torque control without weighting factor is proposed for a voltage source inverter-permanent magnet synchronous motor drive system, which possesses good control performance of torque and stator flux. By investigating the relationship among torque, the reference stator flux amplitude, and the phase angle of the stator flux, the reference stator flux vector is constructed. Then, the reference voltage vector is calculated by the reference stator flux vector based on the delay compensation and the deadbeat control. The extended control set is designed and two generalized base vectors that require further screening are determined based on the position of the reference voltage vector to improve the calculation efficiency. And the duty ratios used for the generalized base vectors are calculated, according to the geometric relations between the generalized base vectors and the reference voltage vector. Finally, by the duty cycle control between two generalized base vectors and between each generalized base vector and zero vector, the candidate vectors are gained and substituted into the cost function only with the flux vector error term. Experiment tests were carried out and the results validated the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper investigates the use of the Taguchi method for the design of line-start permanent magnet synchronous motors (LS-PMSMs). To address the inherent limitation of the Taguchi method in solving multiresponse optimization problems, an improved regression rate methodology and a weighted factor multiobjective technique are incorporated to form a Taguchi method based multiobjective design framework. To validate the proposed method, a prototype machine has been designed, constructed, and experimentally evaluated. It shows that the proposed method can effectively take into account both steady-state and transient synchronization performances in the design of LS-PMSMs. [ABSTRACT FROM AUTHOR]

Multilevel converters with floating capacitors (FCs) are widely applied in recent years in a wide range of industrial applications from high-voltage direct current systems to high power drives. However, some FC topologies lack complete FC voltage balancing capability due to the inherent topology limitation or the insufficient switching state for capacitor balancing. This will result in large ripples on capacitors at low frequency (such as fundamental frequency), limiting their performance and application, particularly, when the fundamental frequency is very low in low-speed drive operations. Typical examples of those multilevel converters are modular multilevel converters (MMC), nested neutral-point-clamped (NNPC) converter, etc. In order to improve the FC balancing for this kind of multilevel converters, this paper proposes a carrier-based pulse-width modulation (PWM) method, named stair edge PWM method. This method can obtain sufficient redundant switching states for FC voltage balancing by producing multiple levels in one PWM period. The FC voltage balancing is thus achieved at switching frequency, which can greatly reduce the capacitor voltage ripple and therefore enable the use of much smaller FCs. Meanwhile, the voltage stress on each device and low $dv/dt$ feature are still the same as the normal multilevel operation, reserving two of the most salient features of multilevel converters. The proposed method also features much simpler and easier implementation compared with space-vector-based approaches, particularly when high-level converters are considered. An application example using a four-level NNPC converter is provided in this paper. The effectiveness and performance of the proposed method are verified by both simulation and experiment. [ABSTRACT FROM AUTHOR]

AC induction motors are the most common motors used in industrial motion. They are widely used in industrial applications for its simplicity, rugged design, low-cost, low maintenance and direct connection to an AC power source. One of the faults occurring in induction motor is the rotor bar breakage that may rapidly spread to a functional failure with catastrophic consequences. Despite the low cost of an induction motor, production losses due to a functional failure in the motor may be greater than the cost of the motor itself. Therefore, the cost advantages that can be achieved with predictive maintenance justify research in monitoring techniques that can indicate the evolution of the conditions before a failure occurs. In this paper, we demonstrate a magnetic sensor based on fiber Bragg grating (FBG) and magnetostrictive composite made of Terfenol-D particulates immersed in epoxy resin matrix applied to induction motor to detect rotor broken bars. To the best of our knowledge, this work demonstrates by the first time an FBG based magnetic sensor applied to monitor an induction motor with the capability to distinguish defective bars, whereas at the same time, conventional technique of current signature at low loading levels failed to indicate the motor severity. The obtained results indicate that the Terfenol-D based sensor can be used for purposes of monitoring broken rotor bars in high voltage induction motors, even when the motor is installed in a dangerous atmosphere, due to the insulation provided by the optical fiber sensor. [ABSTRACT FROM AUTHOR]