Efficiency Of Induction Motor Research Articles

A Simplified Equivalent Circuit Method for Induction Machine Nonintrusive Field Efficiency Estimation

Energy efficiency estimation for in-service induction motors has become a crucial area of research due to the increasing need for energy savings and demand-side management. As a result, several in-service efficiency estimation methods for induction motors have been proposed. This article presents a nonintrusive method for estimating the efficiency of induction motors operating on-site using limited terminal measurements and motor nameplate data. The method uses a modified inverse Г-model equivalent circuit with series core loss arrangement to mitigate the inherent problems of higher computational burden and parameter redundancy in the conventional T-model. Furthermore, a new method is presented for estimating the friction and windage loss using the airgap torque and motor nameplate data. The proposed nonintrusive field efficiency estimation technique was validated experimentally on standard and premium efficiency induction motors for both balanced and unbalanced voltage supply. The results demonstrate the accuracy of the proposed method and confirm its advantage over the conventional method for in-service efficiency determination.

Induction Machine Rapid Performance Test

Efficiency Test Method A is used in industry to determine the efficiency of induction motors. However, in this method, which is carried out by using a dynamometer, the machine under test shall be brought up to its thermal equilibrium before the data can be collected. This requires running the machine under full load for a considerable amount of time (around 8-h), which implies high cost associated with this test. This paper presents a new simple technique that can significantly reduce the time required for induction machine full-load tests. The proposed technique needs only 30 min of a machine run under full-load conditions. The temperature–speed relationship is the key point in this research work. This relationship is utilized to estimate the machine's full-load temperature. The accuracy of the proposed algorithm is validated by testing two small and two medium-sized machines. The results show acceptable level of accuracy, when they are compared to the corresponding 8-h dynamometer tests conducted on the same machines. The technique can save time and cost associated with the dynamometer test. The proposed algorithm is valid only for totally enclosed fan-cooled type induction motors.

Diagnosis of Shaft Misalignment Fault by Piezoelectric Materials to Improve Reliability of Induction Motors

This paper proposes measures to improve the availability and the efficiency of induction motors in industry via the implementation of control shaft misalignment using a piezoelectric material. For this purpose, motors’ failures, which have been extracted from refurbishing and repair workshops, have been used. By performing a critical study and using Pareto analysis, the most frequent failures that have a purely negative effect on the availability and efficiency of induction motors, such as damaged bearings and windings caused by shaft misalignment, which is a common problem in rotating machinery have been identified. An analysis of the induction motor is conducted in order to investigate the waveform by testing the shaft misalignment. This process is performed using a steel shims kit. The vibration signals during machine operation under different misalignment severities are measured. The fast Fourier transform of the signal is generated using National Instruments packages and Matlab software. The experimental results on a 1.1 kW induction motor are analyzed and presented. This paper also shows how shaft misalignment negatively affects induction motor efficiency. The objectives of this applied research are multi-fold; it aims to diagnose machine vibration by piezoelectric materials, to increase the availability of motors, to reduce stopped time caused by misalignment failure, to minimize power consumption and to reduce maintenance costs by generating significant benefits to the company while protecting the environment.

Load extrapolation computational algorithms for energy efficiency measurement testing of high‐power and high‐voltage induction motors

This paper deals with load extrapolation methods and algorithms for the estimation of the energy efficiency of induction motors, starting from the electrical data generally available after parameter identification. The main aim of this paper is to help the readers move from the theoretical analysis to the experimental verification, which is suitable to be included in its own testing. For this reason, step‐by‐step algorithms are included in this paper. The first part deals with the determination of energy efficiency based on an original load extrapolation. Finally, experimental verification of the high‐power and high‐voltage induction motors is provided. Comparison between the values of the in–out method and load extrapolation method confirms the validity of the proposed algorithms. Compared to the direct in–out method, the error of the load extrapolation proposed in this paper is less than 1%.The load extrapolation method is mainly used for the high‐voltage and high‐power asynchronous motor. The high‐voltage and high‐power motor can be used to drive a low‐power motor to achieve coaxial twin trawling in the absence of a suitable power supply and matched load. The energy efficiency of a high‐power motor under different loads are measured and estimated using a mathematical fitting method. The estimated energy efficiency curves in the whole load range can be used to evaluate the high‐power and high‐voltage induction motor. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Maximum efficiency of induction motors considering iron loss resistance

Although there was an extensive amount of research in the area of high efficiency control of induction motors, the equation of maximized efficiency has not been given. The relationship between the source frequency and the motor speed and the equation of efficiency have been derived when the efficiency is maximized for a given torque and speed, and then, they are verified using a single‐phase equivalent circuit considering iron loss resistance. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Subject of the approaches to design asynchronal motors with variable load

The design approaches of variable load induction motors using the criterion of intense quasi-steady-state modes are substantiated. With the help of the proposed criterion, the analysis of serial two-, four-and six-pole induction motors in the power range of 0.09–11 kW was performed. This made it possible to defined induction motors and their parameters (the number of pairs of poles, critical slip, moment of inertia) for which a refined designing is necessary into account the nature of the load. Approaches were tested on the example of the study of the operating modes of three-phase six-pole induction motors with a power of 700 W and 11 kW for single- and two-cylinder piston compressors. The possibilities of increasing the efficiency of induction motors in quasi-steady-state modes by changing the drive inertia moment and selecting the optimal induction motors parameters using the efficiency criterion, which provides the maximum efficiency value for quasistatics, were determined. The feasibility of applying approaches of design is proved by the example of calculating quasi-steady regimes of the six-pole induction motors with a power of 700 W for a two-cylinder compressor. A moment of inertia of the drive was determined, which allows to increase the efficiency in the quasi-steady regimes to its nominal value. It is shown that the optimal design of the induction motors with the constant basic moment of inertia of the drive and the variation in the length of the package and the number of effective stator winding conductors can increase the efficiency in operating modes by 10 %.

A review on MRAS-type speed estimators for reliable and efficient induction motor drives

Induction machines have recently been very popular in variable-speed drives, because of their robust construction and relatively low manufacturing costs (brushless), maintenance-free and well-matured control methods. However, for high-precision control and efficiency optimization one needs the information on the rotor speed which can be measured using different speed sensors. All sensors require a mounting space and cabling, they also generate extra costs and reduce system reliability. Therefore, many of the recent research efforts have been dedicated to sensorless or encoderless electrical drives offering such considerable advantages as: lower cost, reduced size and hardware complexity of the drive system, elimination of sensor cables, lower maintenance requirements, possible operation in aggressive environment, higher noise immunity, reliable and user friendly operation. In this article all well-known sensorless techniques are shortly addressed, but the main focus is on the solutions based on the Model Reference Adaptive System (MRAS) concept. The mathematical models and schemes of all types of MRAS-type speed estimators known from the literature are gathered in this article. The comparative analysis of these speed estimators is done from the following points of view: the speed adaptation mechanism derivation based on the Lyapunov theory, stability problems near zero speed and in the regenerating operation mode, and the sensitivity of MRAS estimators to induction machine parameter changes.

Evaluation of uncertainty for the efficiency of three-phase induction motor using FEA

Evaluation of uncertainty for the efficiency of three-phase induction motor using FEA

The efficiency improvement of AC induction motor with constant frequency technology

Abstract 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.

Standard Efficiency Determination of Induction Motors With a PWM Inverter Source

Induction motor loss segregation and efficiency measurement requires loading dynamometers and other equipment, such as a variable voltage sinusoidal power supply. These are expensive and not often available even when a loading device is accessible. Variable frequency drives are now widely used for operating induction machines and are more widely available and less expensive. However, their use in place of a fixed frequency sinusoidal power supply to directly measure machine efficiency is intriguing, but inherently challenging due to the pulsewidth modulation (PWM) output voltage. This paper presents some investigations for using variable frequency drives to perform IEEE 112B and IEC 60034-2-1 tests. The use of the drive, the measurement criteria, and procedures are reported and discussed. The results presented demonstrate the feasibility of the proposed concept for measuring machine efficiency with a PWM power source.

Multi objective design of high efficiency induction motor using an analytical method's

Multi objective design of high efficiency induction motor using an analytical method's

Assessment of the energy efficiency estimation methods on induction motors considering real-time monitoring

Different methods have been developed to estimate the energy efficiency of induction motors. The accuracy of these methods vary with the load factor, the unbalanced voltage (UV) and harmonics. The feasibility of these methods for efficiency estimation in real-time were theoretically and experimentally assessed during the operation under different operational conditions (i.e. balanced sinusoidal voltage (BSV), harmonics, UV and harmonics with UV). Results show that for load factors over 80%, the air-gap method is applicable under any condition, while the slip method is only applicable under BSV or balanced harmonic voltage. Moreover, for load factors over 40%, the nameplate method is applicable under BSV. Other methods result in errors over 8% and optimization methods are not applicable for real-time monitoring. Electric systems generally operates with some degree of UV and harmonics, while induction motors mostly operate with load factors below 60%, limiting the use of these methods for real-time measurement.

Three autoregressive-neural network hybrid models for energy efficiency estimation of induction motors

PurposeImprovements on the energy efficiency of the induction motors bear on not only these motors but also on the whole industry as a result of preference of these types of motors. In recent projects, energy efficiency of the induction motors is approaching to 90 per cent. The first necessary condition of the efficiency improvements is an accurate estimation of energy efficiency. This study aims to estimate the energy efficiency of induction motors by using three innovative estimation methods.Design/methodology/approachData for 307 motors were taken from three different companies and their torque, power, power factor and speed data were used. Three hybrid models were created by estimating the error of three autoregressive (AR)-based efficiency estimation models with the back-propagation artificial neural network (ANN) structure. In these proposed hybrid models, the AR models were supported with artificial neural networks to obtain a minimum estimation error. These three hybrid models were called as AR1-ANN, AR4-ANN and residual-ANN.FindingsWithout hybridization of AR models by back-propagation ANNs, the best estimation result was obtained by residual model. On the other hand, for the proposed hybrid models, the best estimation was obtained by AR1-ANN, followed by AR4-ANN and finally the residual-ANN according to ME values.Practical implicationsProposed AR-ANN hybrid models relieve of longtime experiments for the energy efficiency measurement of induction motors. Furthermore, these AR-ANN models give more accurate results than the available methods in the literature. Engineering value of this research is three different issues in finding energy efficiency. The first one is minimizing of the test cost, the second one is no requirement the test equipment and the third one is not interrupting the motor. Every company that needs motors can use these estimation methods due to the advantages.Originality/valueNovel three AR-ANN hybrid models for energy efficiency estimation were studied. These novel methods give better response than the other methods which were used for estimation of induction motors in the literature.

Simple and Accurate Algorithm for Small- and Medium-Sized Three-Phase IM Efficiency Estimation Based on No-Load Tests

This paper presents a simple and accurate industrial tool that can be used to estimate the full-load efficiency of three-phase induction motors based on no-load tests. The objective of this research work is to eliminate the need for the expensive dynamometer test, which is available only in well-equipped laboratories and provide electric motor service centers in North America with a user-friendly tool that enables the centers to have their rewound, refurbished, or any existing motors evaluated for efficiency prior to delivery to customers. The proposed technique utilizes a test data of 129 motors, ranging from 1 to 500 hp, tested in Hydro-Quebec Laboratory as per IEEE Std. 112B and CAN/CSA C390 standards procedures. The technique also utilizes a recently proposed stray-load loss formula. The algorithm is validated by recalculating the efficiency of the 195 motors by using the proposed technique. The results show an acceptable degree of accuracy. Error analysis study is conducted to examine the level of uncertainty within the accuracy of the proposed algorithm. The outcome of the study completely supports the algorithm. A spreadsheet-based software is designed to turn the algorithm into a practical user-friendly industrial tool.

Application of a Multilayer AC Winding to Design Synchronous Reluctance Motors

This paper presents the design and experimental validation of a synchronous reluctance motor (SynRM) using a multilayer (ML) ac winding that meets the ultra-premium/IE5 class efficiency requirement. Compared to conventional double-layer ac windings, the ML winding yields a more sinusoidal stator magnetomotive force (MMF) with a shorter end-turn length. The ML winding is characterized using an analytical stator MMF model with verification against finite element analysis (FEA). The proposed winding configuration is optimized under a given design benchmark. The multi-barrier rotor design is also optimized based on FEA using a genetic algorithm. The performance of the designed ML-SynRM is compared against a commercial premium efficiency induction motor and a conventionally wound SynRM for the same standard frame and cooling type. Results show significant efficiency gain with SynRM designs, and also, the designed ML-SynRM yields lower torque ripple with an improved power factor compared to the conventional SynRM. The prototype ML-SynRM is built, and its simulation results are experimentally validated against the benchmark including their performances at a thermal steady state.

Improved hybrid loss control with optimized flux for traction induction motor under light load

With the fast development of rail transportation, it is of great significance to improve the efficiency of traction motors. The efficiency of the traction induction motor may drop drastically when the load is far away from the rated operating point, which is always the case when the vehicle is running under constant speed. This paper presents a loss model control method to achieve the balance between iron and copper losses for efficiency improvement under field‐oriented control. A steady‐state simplified loss model considering iron loss with an equivalent series resistor is built for the expressions of loss and efficiency. Then the optimal flux level is denoted, and the control performance is compared with that of the conventional flux control. The sensitivity of the motor parameters is also studied. Finally, simulation and experimental results validate the feasibility and effectiveness of the proposed control strategy. The experimental results in the laboratory determine the efficiency gains achieved with selected actual traction induction motors. Efficiency gain as high as 3–5% has been achieved under light load conditions. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Alternative Approach to Improving Efficiency Level in Small Induction Motors

In the last few years, new requirements for induction motors efficiency have been imposed. Therefore electrical machines manufacturers have had to redefine their design criteria in order to reduce the losses level with the aim to achieve efficiency values established by the IE2 and IE3 categories of the International Electrotechnical Commission (IEC). Given that, in the near future, is expected to increase the demands regarding efficiency (IE4 and IE5 categories), it is considered appropriate to seek new alternatives to further reduce losses in induction motors. In this work the possibility of using magnetic wedges in induction motors with semiclosed slot is studied. This alternative allows a reduction on copper and core losses of the motor and thus increase their efficiency. The study is aimed at low power motors and considers different permeability and geometries into wedges. Besides the study of losses in the machine, special emphasis is placed on the torque and starting current. Finally, an experimental validation using a 3-kW 380-V 4-pole IE2-class induction motor is presented.

An Improved Non-Intrusive Induction Motor Efficiency Estimation Technique for Non-Ideal Supply Voltage Conditions

Methods of accurately determining the efficiency of motors in situ without costly plant downtime are required to implement online motor management strategies that can lead to energy and cost savings. An ideal method must perform in practical power system conditions where there is variation in the supply voltage. An improved non-intrusive compensated slip technique utilising vibration signature analysis has been proposed for accurately estimating induction motor efficiency. The performance of this technique is evaluated through experimental data under ideal and non-ideal supply voltage conditions. The proposed method of estimating motor efficiency is found to be accurate and easy to implement. The proposed technique is robust in under-voltage and over-voltage power supply conditions.

Induction motor broken rotor bar fault detection techniques based on fault signature analysis – a review

The induction motor is the most popular motor in energy conversion and industrial drive systems. This popularity is due to its robustness, low cost, and easy maintenance. Electrical, mechanical, thermal, magnetic and environmental stresses cause faults in the induction motor during the operation process. One of the challenging topics for many researchers is the development of a reliable efficient induction motor fault diagnostic techniques. The broken rotor bar fault is one of the critical faults that need to be early detected due to its sudden severe damages. The objective of this study is to present a survey of existing broken rotor bar fault detection techniques with new classification based on fault signature. Various monitoring conditions and signal processing techniques are considered for the detection process. A comprehensive list of references is reported for each fault signature and classified based on (i) loading level, (ii) the number of broken bars, (iii) validation and (vi) signal processing.

Challenges in Three-Dimensional Printing of High-Conductivity Copper

With recent advancements in additive manufacturing (AM) technology, it is possible to deposit copper conductive paths and insulation layers of an electric machine in a selective controlled manner. AM of copper enables higher fill factors that improves the internal thermal conduction in the stator core of the electric machine (induction motor), which will enhance its efficiency and power density. This will reduce the motor size and weight and make it more suitable for aerospace and electric vehicle applications, while reducing/eliminating the rare-earth dependency. The objective of this paper is to present the challenges associated with AM of copper coils having 1 × 1 mm cross section and complex features that are used in producing ultra-high efficiency induction motor for traction applications. The paper also proposes different approaches that were used by the authors in attempts to overcome those challenges. The results of the developed technologies illustrate the important of copper powder treatment to help in flowing the powder easier during deposition. In addition, the treated powder has higher resistance to surface oxidation, which led to a high reduction in porosity formation and improved the quality of the copper deposits. The laser powder direct energy deposition (LPDED) process modeling approach helps in optimizing the powder deposition path, the laser power, and feed rate that allow the production of porosity free thin wall and thin floor components. The laser powder bed fusion (LPBF) models identify the optimum process parameters that are used to produce test specimens with >90% density and minimum porosity.