Squirrel Cage Induction Machine Research Articles

Investigation of structure and performance of a permanent magnet vernier induction generator for use in double‐turbine wind systems in urban areas

In this study, a new double-rotor permanent magnet vernier induction wind generator is proposed, which can be connected directly to a double-turbine system used in urban areas. The proposed generator consists of a vernier machine and a squirrel-cage induction machine, which includes a stator and two concentric rotors (a permanent magnet outer rotor and a squirrel-cage inner one). Accordingly, first, the relationships governing the structures of each rotor are presented and investigated. Then, the performance of the generator connecting to a double-turbine system is analysed. Optimisation of the presented generator is investigated by finite-element analysis and also a laboratory prototype is constructed. Finally, both simulation and experimental results are compared, and the reliability of the proposed generator is validated.

Performance of Flywheel Energy Storage System for Fault Ride through Support of Grid Connected Vsc-Hvdc Based Offshore Wind Farms

For the sake of uninterrupted power supply to the loads we are using renewable energy sources. Among them wind energy and the solar energy is the most familiar renewable energy sources we are using now-a-days. Voltage source converter based high voltage DC transmission is considered as future of offshore power transmission. This paper proposes the high voltage DC power transmission system and maintains system balance during each faults. This results in the voltage and current losses on the switching devices. This strategy implements the flywheel energy storage system based on a squirrel cage induction machine connected in parallel to the grid side converter. It is connected in shunt which present on the grid side circuit of VSC-HVDC based squirrel cage induction motor. Due to this the FESS stores the trapped energy in the DC link during AC side faults for long transmission system using a voltage source converter. When there is insufficient of fault meet the grid at load demand. The series of simulation results we carried out the main part of theFESS system under fault conditions achieved using the software Matlab/Simulink. This project possesses the dynamic performance during ‘steady state’ during normal and fault operating conditions.

High-power density induction machines with increased windings temperature

AbstractThe increase of the operating temperature of electrical machines is a major challenge in the context of the large-scale use of electricity in many industrial or individual applications such as mobility. Indeed, working at higher temperatures makes it possible to place electrical actuators in critical areas – such as aircraft engines, for example – and/or to significantly improve the power-to-weight ratio of the machine. For several applications (deep pumping, ventilation, etc.), the use of the induction machine is still preferred due to cost, simplicity and robustness essentially. The objective of this study is to estimate the possibilities of making a high-temperature squirrel cage induction machine. A significant increase in the operating temperature of a machine would indirectly allow us to envisage an increase in the current density in the active conductors and thus a significant improvement in the power-to-weight ratio. However, this is at the sacrifice of efficiency. The aim of this study is to evaluate this decrease in efficiency correlated with the increase in the temperature to find the best compromise according to the relevant applications. An analytic sizing model has been proposed for the prediction of losses, which will be coupled with a thermal model to predict the temperature in different parts of the machine. This study presents essential information on the influence of temperature on the parameters important for the performance of an induction machine.

Analysis of coil pitch in induction machines for electric vehicle applications

This study investigates the influence of stator coil pitch on the electromagnetic performance of squirrel-cage induction machine (IM) with emphasis on the flux-weakening (FW) capability for electric vehicle applications. Three different winding topologies, obtained by changing the coil pitch, namely integer-slot distributed winding (ISDW), integer-slot concentrated winding, and fractional-slot concentrated winding (FSCW), are studied. Their merits and demerits are revealed by comparing their performances characteristics, including winding harmonic index, total axial length, average torque, torque ripple, power losses, efficiency, and FW capability. It is revealed that due to the very high Magnetomotive force (MMF) harmonics induced in the bar current, the bar copper loss of the IM with FSCW is significant. It is also revealed that the parasitic effects of the double-layer winding configurations are lower than those of the single-layer (SL) winding configurations. It is also demonstrated that for the slot/pole/phase combinations lower than two , the higher the coil pitch, the lower the parasitic effects and the higher the efficiency. Moreover, it is found that the combinations , especially those having longer coil pitch and higher stator slot number, and the SL combinations offer better FW capability. Finally, the Finite-element analysis (FEA) results of IM with long-pitch ISDWs are validated by experimental measurements.

Efficient Approach Based on Equivalent Electric Circuit Model to Determine Rotor Bar Currents of Squirrel Cage Induction Machines

Nowadays, finite element method is the most accurate approach to study an electrical machine. However, its use in an optimization process remains often unsuitable because it can still require prohibitive calculation times. An analytical approach would then be more adapted but it should be as accurate as possible. In the case of an analytical model of a squirrel cage induction machine, currents induced in the rotor bars constitute quantities that are difficult to obtain. The equivalent electrical circuit to use should be well adapted and each of its elements has to be accurately estimated. In this article, an equivalent circuit based on bar lumped parameters is proposed and their identification is detailed. The proposed approach is validated through the comparisons of simulation results with the ones obtained by classical FEA in the case of two examples of squirrel cage induction machines with distributed and concentrated armature windings.

Investigation of the power losses in induction machines with rotor eccentricity

Due to manufacturing tolerances and bearing ageing, rotor eccentricity is inevitable in electrical machines. The existence of rotor eccentricity in electrical machines will cause unbalanced magnetic pull (UMP), which would increase bearing friction losses. In addition, the additional magnetic flux harmonics caused by rotor eccentricity may incur additional copper and iron losses. Here, induction machines are analysed as they are more sensitive to rotor misalignment due to smaller air gap compared to other types of machines. The magnetic flux distribution and UMP for both squirrel cage and wound rotor induction machines are discussed, as they have a dissimilar rotor configuration. The existence of rotor eccentricity would increase rotor copper loss in squirrel cage induction machines and would increase iron losses in wound rotor induction machines, where the additional power losses are a function of the degree of eccentricity. Analytical models are used to estimate the additional power losses, and they were validated using finite element analysis. Finally, we investigated the impact of power losses when implementing the slip control method which is proposed in our previous literature, in order to reduce UMP.

A Histogram of Oriented Gradients Approach for Detecting Broken Bars in Squirrel-Cage Induction Motors

This article presents a novel approach for detecting broken rotor bars in squirrel-cage induction motors, using a time-domain current analysis. More particularly, this solution proposes a new use of histogram of oriented gradients since this method is usually applied in computer vision and image processing applications. Fully broken rotor bars have been detected when the motor was running at a very low slip since this operational condition is very difficult to identify using the traditional motor-current signature analysis. In addition, only one phase of the stator current of the machine was applied to extract the intensity gradients and edge directions of each current time window, for both healthy and damaged rotors. It is important to highlight that the present method does not require the slip measurement for fault detection, as demand for other techniques and often related to false negative indications. The features extracted from the histograms have been applied as inputs for a neural network classifier. This method has been validated using some experimental data from a 7.5-kW squirrel-cage induction machine running at distinct load levels (slip conditions) and also for oscillatory loads.

Equivalent 3-Level PWM: An Improved Technique to Reduce Torque Ripple in DI-WRIM Analyzed as DI-OWIM

In the supersynchronous mode of double-inverter-fed wound rotor induction machine (DI-WRIM) drive, torque ripple is dependent on the sum of the quadrature ( $q$ ) axis stator and rotor flux ripples (termed as overall flux ripple). Therefore, in the existing method, the torque ripple is reduced by merely changing the slope of one of the flux ripples such that their sum is reduced. However, the torque ripple can be further reduced, as the overall flux ripple in DI-WRIM resembles the $q$ -axis stator flux ripple of a double-inverter-fed open-end winding induction machine which is generally analyzed as a three-level neutral-point-clamped inverter fed squirrel cage induction machine (SQIM) (3L-SQIM) drive. Thus, in this article, the stator and rotor voltage source inverters are switched together and the resemblance is explored to develop stator–rotor pulsewidth modulation (PWM) combinations, such that the overall flux ripple is equivalent to the $q$ -axis flux ripple of 3L-SQIM. The effect of phase shift between the stator and rotor voltage vectors on torque ripple is analyzed and a hybrid PWM combination is also proposed to minimize the same. The reduction in torque ripple, with the proposed combinations, is validated in terms of the estimated instantaneous and RMS torque ripples. The simulation and experimental results further validate this reduction.

A grid-connected variable-speed wind generator driving a fuzzy-controlled PMSG and associated to a flywheel energy storage system

In this paper, we propose a variable speed-wind energy conversion system based on a permanent magnetic synchronous generator (PMSG). A complete system model with multiple controllers is proposed and simulated. Two controllers are proposed and examined for regulating the current from the PMSG, the first is a simple PI controller and the second uses a fuzzy component to improve the tracking performance. A flywheel energy storage system (FESS) is associated to the proposed variable speed wind generator (VSWG). The FESS is linked at the DC bus stage in order to regulate the power supplied to the grid. In simple terms, if the generated power exceeds the demand, the excess is stored by the FESS for use when a shortage occurs. In this scenario, the VSWG is controlled to capture the maximum wind energy by means of the maximum power point tracking (MPPT) method. To maintain this operation as the turbine speed increases above the rated speed, we implement a pitch angle controller. The FESS is based on a squirrel-cage induction machine (IM) coupled to a flywheel. A controlled grid converter allows for the exchange of active and reactive powers with the grid. A proportional integral (PI) based grid connection is proposed that controls the current and voltage amplitudes as well as the frequency passed onto the grid. The aim of the converter control is to achieve a decoupled active and reactive power control suitable for operation at a unitary power factor. The dynamic model of the proposed system is simulated using the Matlab–Simulink package. The obtained results are presented and discussed to illustrate the performance of the overall proposed system.

Sensorless control of wind power generator with flywheel energy storage system

For the purpose of sensorless low-speed control of direct-drive permanent magnet synchronous generator–based wind power systems, a technique based on the rotating high-frequency voltage-signal injection is discussed in this article, which improves the efficiency of the method and eliminates the phase shift introduced by traditional filters; band pass and low-pass filters are replaced by an extended complex Kalman filter algorithm. In addition, a flywheel energy storage system based on a squirrel cage induction machine is connected with the wind power generator by a DC bus through two power converters. For sensorless control of the induction machine, a rotor speed estimation method based on the extended complex Kalman filter is established. Finally, network connection interface of the complete system is presented and the efficiency of the proposed sensorless control of the whole chain of wind power generation is shown by numerical simulations using MATLAB/Simulink environment.

Performance and Loss Analysis of Squirrel Cage Induction Machine Based Flywheel Energy Storage System

Flywheel energy storage systems (FESS) are one of the earliest forms of energy storage technologies with several benefits of long service time, high power density, low maintenance, and insensitivity to environmental conditions being important areas of research in recent years. This paper focusses on the electrical machine and power electronics, an important part of a flywheel system, the electrical machine rotating with the flywheel inertia in order to perform charge-discharge cycles. The type of machine used in the electrical drive plays an important role in the characteristics governing electrical losses as well as standby losses. Permanent magnet synchronous machine (PMSM) and induction machines (IM) are the two most common types of electric machines used in FESS applications where the latter has negligible standby losses due to its lower rotor magnetic field until energised by the stator. This paper describes research in which the operational and standby losses of a squirrel-cage induction machine-based flywheel storage system (SCIM-FESS) are modelled as a system developed in MATLAB/Simulink environment inclusive of the control system for the power electronics converters. Using the proposed control algorithm and in-depth analysis of the system losses, a detailed assessment of the dynamic performance of the SCIM-FESS is performed for different states of charging, discharging, and standby modes. The results of the analysis show that, in presence of system losses including aerodynamic and bearing friction losses, the SCIM-FESS has satisfactory characteristics in energy regulation and dynamic response during load torque variations. The compliance of FESS and its conversion between the generating and motoring mode within milliseconds show the responsiveness of the proposed control system.

Analysis of Transient Magnetic Force on End-Winding in the Inverter-Fed Induction Machine

The increasing harmonics caused by inverter supply have an adverse impact on the end-winding vibration of the induction machine in accelerating failure and adding noise. Therefore, this paper puts forward an approach for end-winding magnetic force calculation in the inverter-fed induction machine. The 2D field–circuit–motion coupling analysis is used to calculate the stator currents in an induction machine, which are taken as loads in 3D transient magnetic analysis to obtain magnetic force on the end-windings. A three-phase squirrel-cage induction machine was designed and an experiment was carried out on the test motor to validate the proposed model. The simulated stator current, magnetic flux density and magnetic force agree well with both the theoretical analysis and measured results. Finally, a 3-D transient structural simulation was performed to further analyze the end-winding vibration. However, there is some difference of end-winding vibration acceleration between the simulation and experiment in harmonic components. The above deviation is probably attributed to the structure simplification of the induction machine. Thus, the developed simulation model can calculate the magnetic force on end-winding with reasonable accuracy, but it is advisable to perform an experimental study to fully analyze the vibration characteristics of end-winding.

Parallel Operation of Three-phase Self-excited Induction Generators Driven by Renewable Energy Sources

Squirrel-cage induction machines, because of their low prices and rare demand for maintenance, can work as self-excited induction generators (SEIGs) in remote areas to convert wind or pico-hydro power to electricity, enhancing the use of different forms of renewable energy. However, with the increase of load, a single SEIG may not provide enough capacity to meet the demand, so parallel operation of several SEIGs is often required, necessitating a technique to analyze the characteristics of this kind of operation. This paper presents steady-state analysis of two SEIGs based on the equivalent circuit of the induction generator. The two-machine model allows the performance and load sharing features to be evaluated when the two generators undergo different rotating speeds.

Classification and Detection of Faults in Induction Motor using Dwt with Deep Learning Methods under the Time-Varying and Constant Load Conditions

This article proposed a method to detect the faults in multi-winding induction motor using Discrete Wavelet transform combined with Deep Belief Neural Network (DBNN). This technique relies on the instantaneous reactive power signal decomposition, from which detail coefficients and wavelet approximations are extracted which are termed as features. In order to obtain a robust diagnosis, this article proposed to classify the feature vectors extracted from DWT analysis of power signals using DBNN (Deep Belief Neural Network) to distinguish the motors state. Subsequently, in order to validate the proposed approach, a three phase squirrel cage induction machine is simulated under MATLAB software. To check the effectiveness of the proposed method of fault diagnosis the motor is simulated in different simulation environments like time varying load and constant load condition. Promising results were obtained and the performance of DBNN i.e. 99.75% accuracy. The proposed algorithm is compared with various other state-of-art methods and the comparison proves its robustness in diagnosing the fault in motors.

Data‐driven online temperature compensation for robust field‐oriented torque‐controlled induction machines

Squirrel-cage induction machines (IMs) with indirect field-oriented control are widely used in industry and are frequently chosen for their accurate and dynamic torque control. During operation, however, temperature rises leading to changes in machine parameters. The rotor resistance, in particular, alters, affecting the accuracy of the torque control. The authors investigated the effect of a rotor resistance parameter mismatch in the control algorithm on the angular rotor flux misalignment and the subsequent deviation of stator currents and motor torque from their setpoints. Hence, an online, data-driven torque compensation to eliminate the temperature effect is proposed to enable robust torque-controlled IMs. A model-based analysis and experimental mapping of the temperature effect on motor torque is presented. A temperature-torque lookup-table is subsequently implemented within the control algorithm demonstrating the ability to reduce the detrimental effect of temperature on torque control. Experimental results on a 5.5 kW squirrel-cage induction motor show that the proposed data-driven online temperature compensation method is able to reduce torque mismatch when compared to having no temperature compensation. Up to 17% torque mismatch is reduced at nominal torque and even up to 23% at torque setpoints that are lower than 20% of the nominal torque. A limited torque error of <1% remains in a broad operating range.

Squirrel-Cage Rotor Design and Manufacturing for High-Speed Applications

A high-speed squirrel-cage induction machine requires a totally different design compared to the traditional squirrel-cage industrial motor because of the mechanical limitations caused by the high speed. This results in a more complicated rotor construction and expensive material selection, and sets higher standards for the manufacturing precision. The objective of this paper is to demonstrate the design aspects, material selection, and manufacturing of a squirrel-cage rotor for high-speed applications. In this paper, the rotor dimensioning approach based on equations and data analysis is presented. Rotor material selection and construction topology influence on the electrical machine design are discussed. The results are illustrated with the design of a 6-kW, 120 000-r/min induction machine for a turbo circulator. The influence of rotor parameters on the electromagnetic performance of the designed machine is demonstrated. Mechanical stresses for different topologies are studied with finite-element method analysis. Several manufacturing methods for producing a high-precision rotor are described and compared. The presented rotor design approach, which enables high electromagnetic performance and robust construction, is verified by the testing of a prototype.

Induction Machine Parameters Determination and the Impact of Stator/Rotor Leakage Split Ratio on Its Performance

The relationship between the stator and rotor leakage reactance of the induction machine (IM) according to IEEE Std 112 is assumed to be constant under all operating conditions. However, this is not substantially accurate during severe transients such as the direct online startup and loading conditions of a three-phase induction motor. The leakage reactance of the machine can vary widely during severe conditions. Hence, using constant parameters in the machine model will result in an inaccurate dynamic performance prediction. Moreover, considering a constant ratio between the stator and rotor leakage reactance is no longer valid for all current levels. In this article, a direct and precise method is proposed to estimate and separate the stator and rotor leakage reactance parameters under normal operating conditions and when the core is deeply saturated. The method exploits the two-dimensional time-stepping finite-element method (FEM) with a coupled circuit. The obtained current-dependent reactance functions in both leakage flux paths are included in the dq-model of the IM. Other machine parameters are determined by implementing the standard tests in FEM. To verify the effectiveness of the proposed method, the predicted results are compared to the dynamic responses obtained experimentally from a three-phase, 5-hp squirrel cage IM.

Investigation of the unbalanced magnetic pull damping effect in squirrel cage induction machines

The unbalanced magnetic pull (UMP) in electrical machines is due to the existence of additional p ± 1 magnetic flux waves. When squirrel cage induction machine (SCIM) running below its rated slip, most of the additional magnetic flux waves can be damped by the counteracting flux waves produced by its parallel-connected rotor bars. Here, this UMP damping effect is comprehensively discussed by comparing the UMP and the air-gap flux of SCIMs and wound rotor induction machines. Subsequently, a UMP damping coefficient is proposed to be included in the conventional UMP analytical model, in which the damping of UMP caused by the counteracting flux waves can be taken into account. Lastly, the UMP of SCIM at different excitation frequencies and rotor resistance are investigated to further verify the UMP damping effect.

Fuzzy-Based Statistical Feature Extraction for Detecting Broken Rotor Bars in Line-Fed and Inverter-Fed Induction Motors

This paper presents the use of a fuzzy-based statistical feature extraction from the air gap disturbances for diagnosing broken rotor bars in large induction motors fed by line or an inverter. The method is based on the analysis of the magnetic flux density variation in a Hall Effect Sensor, installed between two stator slots of the motor. The proposed method combines a fuzzy inference system and a support vector machine technique for time-domain assessment of the magnetic flux density, in order to detect a single fault or multiple broken bars in the rotor. In this approach, it is possible to detect not only the existence of failures, but also its severity. Moreover, it is not necessary to estimate the slip of the motor, usually required by other methods and the damaged rotor detection was also evaluated for oscillating load conditions. Thus, the present approach can overcome some drawbacks of the traditional MCSA method, particularly in operational cases where false positive and false negative indications are more frequently. The efficiency of this approach has been proven using some computational simulation results and experimental tests to detect fully broken rotor bars in a 7.5 kW squirrel cage induction machine fed by line and an inverter.

Influence of stator and rotor geometric parameters on rotor bar current waveform and performance of IMs

In this study, the influence of the stator and rotor geometric parameters on the rotor bar current waveform and performance characteristics of a squirrel-cage induction machine (IM), based on a slot/pole number combination (48-stator slot/8-pole/52-rotor slot), with the same winding layout, stator outer diameter, stack length, stator current, and rated speed as the Toyota Prius 2010 interior permanent magnet machine, is investigated. In order to reveal the individual influence of each parameter, parametric analyses have been conducted for each geometric parameter, and the corresponding variations of torque, torque ripple, power losses, and efficiency are numerically studied. It has been shown that in addition to rotor slot width, rotor slot depth, and stator slot width, corresponding to rotor tooth width, rotor tooth height, and stator tooth width, respectively, have a significant effect on the bar current waveform and performance characteristics while the slot opening widths have the least effect.