Large Induction Motors Research Articles

Mitigation of voltage sag and voltage swell by using dynamic voltage restorer

Recent power quality (PQ) research shows that the most common types of power quality disturbances are voltage sags and swells in medium and low-voltage distribution grids. This paper shows how to improve two significant power quality disturbances: sags and swells voltage. To find out what effect these two PQ issues have in real life, a study case based on real nonlinear loads data from large induction motors at Beshai Company in Sadat City in Egypt is investigated. The dynamic voltage restorer (DVR) has been suggested as a solution to the voltage swell and voltage sag issues. The point of common coupling (PCC) is linked with the dynamic voltage restorer to mitigate the PQ problems that have been found. The power network, loads, and DVR may all be modeled using the MATLAB/Simulink platform. The jellyfish search optimizer (JFS) is used to get the gain settings of the proportional and integral (PI) controller for the proposed DVR. MATLAB/Simulink's results show that the proposed device is effective, reliable, and has low latency.

Power Compatibility of Induction Motors in Industrial Grids Containing Synchronous Generators

Starting an induction motor causes voltage sag in the industrial grid that may disturb the operation of grid equipment. Direct-on-line starting is the simplest and most cost-effective method for starting induction motors, but also the most problematic. Large industries often use internal power plants with synchronous generators and starting powerful motors may impact the generator operations. The synchronous generators could be operated with the automatic or manual mode of voltage control. As the operation experience proves, the generator voltage control mode has a significant impact on the transient behaviours in the industrial power grid when starting a large induction motor. This article presents a case study of the synchronous generator tripping within a true medium-voltage industrial grid during the direct-on-line starting of a large induction motor driving the feed water pump. An analysis of the generator protection logs after the tripping showed that the synchronous generator was controlled in manual mode and its protection relay settings were exceeded. The transients initiated by induction motor starts were studied for possible configurations and operating conditions of the grid using a model developed on the Matlab/Simulink Software platform. The simulations have shown that concern about starting large motors in industrial grids containing internal synchronous generators needs to be solved considering the grid configurations and the coordination of generator protection and control devices.

Permanent Magnetization Transformation and Performance Analysis of Small Power Three Phase Asynchronous Motor

Oilfield pumping units are the main production machinery in the oilfield, and the electricity consumed accounts for about 60% of the oilfield’s electricity consumption. The requirements of the pumping unit for the electric motor are high starting torque, high efficiency, and a wide economic operating range. If an induction motor is used, in order to meet the requirements of high starting torque of the pumping unit, it is necessary to configure a large capacity induction motor. However, during normal operation, the average load rate is low, mostly under light or no-load operation, the efficiency and power factor are low, resulting in a large amount of waste of electrical energy. In this paper, the permanent magnetization of the induction motor is proposed. The stator remain unchanged, only grooves (straight/inclined) are cut on the outer surface of the rotor to place permanent magnets. The original asynchronous motor is converted to a permanent magnet motor. It can be used in actual oilfield exploitation engineering.

Designing a Smart Inverter for Compensating the Voltage Sag Caused by Motor Start-up

Starting a large induction motor will always follow up with an inrush current as the nature of an induction motor. On a less stiff power system, that inrush current will be causing a Voltage Sag (VS). A big VS can lead to significant disruptions in power quality and reliability. To address this, a Smart Inverter with an Artificial Intelligence (AI) -driven controller installed in a Photovoltaic (PV) farm is proposed for voltage sag recovery. During normal conditions, the PV farm acts as a power source supporting the main grid, but when large induction motors are started, the smart inverter connected to the PV is responsible for power conversion to recover sags caused by the Induction motor inrush current. The controller inside the Inverter ensures optimal operation. The use of AI also compares the effectiveness of using the Fuzzy Logic Controller (FLC) with the Proportional Integral (PI) Controller to assess their performance in reducing current spikes. Based on simulations, the FLC outperformed PI Controller in mitigating the voltage sag and avoiding the Low Voltage Ride-Through (LVRT). Simulation results show that voltage sag can be recovered for up to 97% of the nominal voltage, a significant improvement over the 80% sag recovery without the smart Inverter. At a nominal grid voltage of 6,600 volts, the VS Magnitude was successfully increased from 5,210 volts to 6,368 volts and the VS Duration also decreased from 6.96 s to 4.97 s. The results achieved validate the effectiveness of the approach in improving the power quality.

Optimum estimation of series capacitors for enhancing distribution system performance via an improved hybrid optimization algorithm

AbstractAs the load on distribution networks grows, system operators and planners are constantly challenged with the issue of voltage regulation or enhancing the quality of supply to customers at the load end of lengthy distribution lines. This paper presents the optimum determination of series capacitor units in a distribution system to maximize energy‐saving and enhance voltage levels. Interestingly, series capacitors can enhance the capability of transmission lines, reduce line losses, enhance the performance of buses with large induction motor loads and reduce voltage flicker. At the same time, the limitations of series compensation are taken into consideration while calculating its optimum values. To achieve the planning objective and optimal load flow objective, two strategies: The Improved Grey Wolf Optimization method (I‐GWO) and Tabu Search (TS), are hybridized to get the benefit of their advantages. The I‐GWO has a movement strategy called dimension learning‐based hunting for enhancing the balance between global and local search and maintaining diversity. The proposed (I‐GWO‐TS) algorithm can solve mixed‐integer programming to achieve the planning and the optimal load flow objectives. The proposed method can be applied to a real Egyptian distribution system that is heavily loaded, with poor voltage regulation, and also has high‐power losses. The obtained results demonstrate the capability of the proposed approach to determine optimal series capacitors’ location and sizing for maximization of energy saving. Further, the proposed method improves the network performance regarding the voltage profile and power losses, although the limitations of including series compensation were considered in the distribution system.

Power quality improvement of large power induction motor drive using three-level front-end converter

PurposeThe purpose of this study is to provide the enhancement of power quality of a high power-rated voltage source inverter driven induction motor with a three-phase, three-level neutral point clamped converter placed at the front end, while a passive power filter is connected in shunt with it. The improvement in power quality can be achieved by reducing the total harmonic distortion in source current. The controllers were designed for the linearization of the high-power induction motor drive. A control method is presented for the regulation of the common DC-link voltage.Design/methodology/approachThe induction motor is modeled using its dynamic equations, and a decoupling controller is designed to linearize the nonlinear dynamics of the drive through feedback. The common DC-link voltage of the proposed front-end connected converter is monitored and controlled through a control method which feeds the pulse width modulated inverter that drives the induction motor. A passive power filter is designed to meet the reactive power requirement of the system in addition to improve the power quality.FindingsSimulations were carried out for the proposed topology of the drive mechanism, and the outcomes were analyzed by a comparative analysis of the drive system both in the presence of the passive filter as well as in the absence of the filter. The total harmonic distortion is found to be reduced enough to meet the standards with the designed filter, and the reactive power is also compensated considerably. The input power factor at the supply side is maintained almost to unity, and the DC-link voltage of the proposed circuit topology is maintained at the desired level. The overall performance of the drive system was found to be useful and economical.Originality/valueA new topology of a front-end connected three-level neutral point clamped converter to a high power-rated induction motor drive is proposed. The drive is fed by a pulse width modulated inverter with a common DC-link with the front end connected converter. A passive filter is designed with respect to the reactive power requirement of the system and connected in shunt to the converter at the supply side. Control schemes are designed and used for the drive system and also for the regulation of the common DC-link voltage of the proposed front end connected converter.

Optimal capacitor placement in a dominant induction motor loads power system

The challenge of optimal capacitor allocation is one of the complex problems in power systems, especially in large industries since they have many big capacity induction motors. In the literature, many works have been delivered for optimal capacitor placement, however, these works were simulated in a distribution network, not in an industry network with many large capacity induction motors. Therefore, this work proposes the optimal allocation of capacitors in a large industry with a significant amount of induction motor loads to minimize network losses. To determine the optimal capacitor location, this research uses the genetic algorithm (GA) method. This algorithm is interesting because of its simplicity and ability to discover optimal solutions comprehensively.

Impact of Aspect Ratios of Solid Rotor, Large Air Gap Induction Motors on Run-Up Time and Energy Input

This article introduces a unique three-phase induction machine with a large air gap and a copper-coated iron cylinder. The motor is built in an X-ray tube for medical applications where key performance indicators are the start-up time, generated rotor, and total energy during the run-up. The common equivalent circuit for induction motors is utilized to systematically analyze the effect of the rotor protrusion length variation on these key performance indicators by means of three-dimensional (3D)-FEA. However, due to the large air gap and dominating winding head standard evaluation tools, such as the no-load and locked-rotor tests do not provide accurate circuit parameters. Thus, a combined no-load and locked-rotor test evaluation is introduced. Furthermore, to avoid the time and computational effort of time-stepping 3D-FEA, time harmonic and static 3D-FEA is introduced. To validate these simplified 3D-FEA simulations, results are compared with the selected time-stepping 3D-FEA results. Experimental results verify the 3D-FEA results. After establishing a routine to identify accurate equivalent circuit parameters by means of 3D-FEA, the parameters for three different stator lengths each combined with six different rotor lengths are identified. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V/f</i> -controlled run-up simulations are then conducted to generate the results. Results quantify the tradeoff between start-up time, generated rotor, and total energy depending on the rotor protrusion, e.g., the start-up time is indirectly proportional to the rotor protrusion and directly proportional to the rotor frequency (the relative frequency between stator field and rotor speed). The effect of the rotor temperature, which can reach up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 390^\circ \,$</tex-math></inline-formula> C, on the results is included.

Reduction of Starting Current in Large Induction Motors

Large induction motors can have a high inrush and run-up current during starting, often up to ten times the rated current. In weak supplies, this could be a problem, causing system stability issues and the voltage to dip below acceptable levels. In islanded systems, the capacity could be pulled below its maximum. There are several different starting methods possible, but they are often only suitable for smaller machines. One method not investigated is the use of parallel capacitor compensation during the starting because large induction motors are very inductive during the starting sequence, so that supplying reactive power may be more effective than supplying energy. This paper first investigates several different induction motors with increasing size and assesses their compensation requirements in terms of the reactive power requirement during starting. It is shown that they do generally become more inductive as they increase in size. It is illustrated, using simulations, that using parallel capacitors during starting can significantly reduce the starting current. The concept is tested using a small experimental motor. Series inductors are added to the motor to make it more inductive and look more like a larger machine. The experimental results confirm that the method works. It is also found that the parallel capacitors require series filters to prevent harmonic current, and these can be realized using inductors in series with the compensation capacitors. Point-on switching using solid-state relays was tested, and these can reduce the transient switch-on current over the first voltage cycle.

An Expert System for Rotating Machine Fault Detection Using Vibration Signal Analysis.

Accurate and early detection of machine faults is an important step in the preventive maintenance of industrial enterprises. It is essential to avoid unexpected downtime as well as to ensure the reliability of equipment and safety of humans. In the case of rotating machines, significant information about machine’s health and condition is present in the spectrum of its vibration signal. This work proposes a fault detection system of rotating machines using vibration signal analysis. First, a dataset of 3-dimensional vibration signals is acquired from large induction motors representing healthy and faulty states. The signal conditioning is performed using empirical mode decomposition technique. Next, multi-domain feature extraction is done to obtain various combinations of most discriminant temporal and spectral features from the denoised signals. Finally, the classification step is performed with various kernel settings of multiple classifiers including support vector machines, K-nearest neighbors, decision tree and linear discriminant analysis. The classification results demonstrate that a hybrid combination of time and spectral features, classified using support vector machines with Gaussian kernel achieves the best performance with 98.2% accuracy, 96.6% sensitivity, 100% specificity and 1.8% error rate.

Features of an induction motor design taking into account the possible operation in the mode of electrical asymmetry of the windings resistances

The paper examines the operation of large high-voltage induction motors used as an electric drive of critical installations in enterprises with a continuous production cycle. The theoretical foundations of the appearance of a dip in the mechanical characteristic of an induction motor in the mode of winding resistances asymmetry are considered. The developed power supply device for an induction motor with torque dip compensation at electrical asymmetry of phase windings appears is presented. The necessity of introducing a service factor is formulated to take into account the decrease in the total level of the electromagnetic torque in such operating modes, which is carried out at the stage of the motor design beginning.

리액터 기동 유도전동기의 가속 시간에 관한 연구

Induction motors have a simple structure, easy maintenance, and constant speed operation, so they are most often used as driving equipment for fluid loads such as pumps. Induction motors have a disadvantage that voltage drops occur due to high current generation during startup. In order to overcome this problem, various starting methods are applied according to the motor capacity. In the case of medium and large induction motors, the reactor starting method is widely applied. The calculation of the acceleration time by the reactor starting is important for the electrical quality analysis of the system. The calculation of acceleration time is complicated because it must go through the process of differential and speed integration for the torque difference between the motor and the load. Therefore, in this study, we compared and analyzed the calculation of the acceleration time through the introduction of the simplified calculation of the acceleration torque and the simulation of the actual model through the electromagnetic transient analysis program.

Evaluating voltage drop snapshot and time motor starting study methodologies—An offshore platform case study

This paper presents a comparison between static (Snapshot) and dynamic (Time Study) motor starting study methodologies in terms of buses voltage drop and power flow, using a case study of an offshore platform. For this purpose, the Power Tools for Windows (PTW) software and the real-time digital simulator (RTDS) were used to performing the analysis of the Snapshot and Time-Domain methodologies, respectively. The investigation has focused on differences in the parameter requirements necessary for each methodology, with a special application in a complex isolated system, such as the case of an offshore platform typical composed of synchronous generators and the large induction motors. The advantages and disadvantages of each methodology will be analyzed according to the strict operating and handling requirements of an actual offshore platform. Simulation results demonstrated that a motor starting study in the time domain contributes better information than the static one, even more for this type of particular system. This work reveals the need that selection criterias between the two methodologies must be defined in the IEEE 3002.7–2018 standard and for isolated systems is highly recommended to perform an analysis in the time domain.

Simulation &amp;amp; Analysis of an Asynchronous Electric Motor for various Abnormal conditions

Asynchronous electric motor has its optimum working state under its rated values. In real scenarios, these conditions cannot be provided always. This leads to problems in the electric motor. Through simulation and analysis of the induction motor under various abnormal conditions, we could study the variation of the stator current and thereby study the motor. The study is conducted using Pulse width modulation and also by using Space vector modulation for driving the inverter and the stator current is analyzed for both the conditions. The multiresolution analysis is a powerful method for the analysis of the motor working under abnormal conditions and is useful for its study. Along with these abnormal conditions, there are various other reasons causing damages to the electric motor. One among them is the eccentricity fault. They are mainly seen in large induction motors. By thorough analysis of the induction motor under various abnormal conditions and faults, we could train an ANN to detect the faults in the system or to identify the modulation used in the drive, from the stator current of the motor.

Influence of modern magnetic and insulation materials on dimensions and losses of large induction machines

AbstractThe aim of this study is to present the possibilities of reducing the size of large induction motors with new electrical materials taken into account of thermal constraints. This study highlights the possibilities of reducing losses, increasing the efficiency, and decreasing the weight, by taking different grades of materials. A nonlinear multiobjective optimization is used to determine the best solution, by varying the internal and external geometric parameters.

대용량 전동기의 기동특성을 고려한 비상용 에너지 저장장치 용량산정에 대한 연구

대용량 전동기의 기동특성을 고려한 비상용 에너지 저장장치 용량산정에 대한 연구

A convex model for induction motor starting transients imbedded in an OPF-based optimization problem

Large horsepower induction motors play a critical role in the operation of industrial facilities. In this respect, the distribution network operators dedicate a high priority to the operational safety of these motor loads. In this paper, the induction motor starting is modeled analytically and in a semi-static fashion. This model is imbedded in a convex distribution system restoration problem. In this optimization problem, it is aimed to determine the optimal status of static loads and the optimal dispatch of distributed generators such that: a) the induction motors can be reaccelerated in a safe way and, b) the total power of static loads that cannot be supplied before the motor energization, is minimized. The proposed optimization problem is applied in the case of a distribution network under different simulation scenarios. The feasibility and accuracy of the obtained results are validated using a) off-line time-domain simulations, and b) Power Hardware-In-the-Loop experiments.

Speed Estimation During the Starting Transient of Induction Motors

Typically, the rotor speed of electric motors was measured directly by the use of electromechanical sensors. Even though these devices are very precise, they are also fragile and expensive to install. Currently, some alternatives are based on speed estimations from the measurement of stator currents. Some of these, very accurate, are used in variable speed drives. In industrial power applications, many large induction motors (IMs) are directly driven with special starters. For these cases, new speed estimation strategies must be developed. This article presents a self-sensing method for speed estimation during the starting transient of both wound rotor and squirrel cage IMs. The speed estimation is based on the simultaneous tracking of multiple harmonic components of the rotor on the spectrogram of the stator currents in sequence networks. The proposal is validated with experimental results obtained in the laboratory with a squirrel cage IM. It is concluded that the estimation is not sensitive to measurement noise and tracking errors caused by other harmonic components that do not depend on the rotor position.

Power factor correction of the industrial electrical system during large induction motor starting using ETAP power station

This paper presents the power factor correction of the electrical system during the induction motor starting using ETAP power station. There are some problems faced by the electrical system when the motor is started, including voltage drop, high insulation current, and low power factor. The starting motor method used in this paper is starting with VFD. The aim of this research is to improve the power factor during the starting time. The system with a capacitor resulted in a low power factor that lowers the quality of electrical power. By adding capacitor 30 kVAR with each step 0.1 kVAR in the system, the power factor increased to 95.5%.

Optimal Load Restoration in Active Distribution Networks Complying With Starting Transients of Induction Motors

Large horsepower induction motors play a critical role as industrial drives in production facilities. The operational safety of distribution networks during the starting transients of these motor loads is a critical concern for the operators. In this paper, an analytical and convex optimization model is derived representing the starting transients of the induction motor in a semi-static fashion. This model is used to find the optimal energization sequence of different loads (static and motor loads) following an outage in a distribution network. The optimization problem includes the optimal control of the converter-based DGs and autotransformers that are used for the induction motor starting. These models together with the semi-static model of the induction motor are integrated into a relaxed power flow formulation resulting in a Mixed-Integer Second Order Cone Programming (SOCP) problem. This formulation represents the transient operational limits that are imposed by different protection devices both in the motor side and network side. The functionality of the proposed optimization problem is evaluated in the case of a large-scale test study and under different simulation scenarios. The feasibility and accuracy of the optimization results are validated using I) off-line time-domain simulations, and II) a Power Hardware-In-the-Loop experiment.