Locked Rotor Conditions Research Articles

Current Signature Analysis for Diagnostics in Motor Bars under Locked Rotor Condition

Three-phase induction motors are widely used in industrial electric applications. To ensure their operability, efforts have been made mainly in the detection of rotor faults. This work aims to detect rotor faults in induction motors through of Motor Current Signature Analysis (MCSA) under locked rotor condition. In this configuration, the procedure is most suitable for drives where the motor operates intermittently, with a short operating stroke or variable speed. This paper proposes a methodology and presents a comparison of consolidated signal processing techniques such as Fast Fourier Transform (FFT), Discrete Wavelet Transform (DWT), and Discrete Hilbert Transform (DHT) applied on the conventional input currents and components of Park transformation in a case study. The objective is to define which of the techniques is the most robust in the process of identifying broken bars in the induction motor for the proposed methodology.

Fatigue Life Analysis of Automotive Glass Regulator Based on ABAQUS and FE-SAFE

Taking automotive glass regulator (glass regulator for short) as investigative object, fatigue life of glass regulator in top dead center locked-rotor condition is analyzed by adopting the combined simulation of ABAQUS and FE-SAFE. Firstly, calculation criterion of fatigue life of glass regulator and the combined simulation steps of analyzing fatigue life of glass regulator are investigated. Afterwards, HYPERMESH is used to generate mesh of glass regulator and ABAQUS is used to finite element analyze glass regulator. Then, stress condition is obtained. Finally, stress condition, material fatigue property, loading spectrum are imported into FE-SAFE for analyzing fatigue life, and fatigue life nephograms are gained. Fatigue life nephograms suggest that fatigue life of plate curved part on slider, flanging on guide rail, the part near the mounting hole of guide pulley are short, on which risk of fatigue failure exists. This method provides theoretical basis for design of fatigue life of glass regulator.

Current-Scaling Gain Compensation of Motor Drives Under Locked-Rotor Condition Considering Inequality of Phase Resistances

This article proposes a current-scaling gain-compensation algorithm for motor drive applications under the locked-rotor condition. In heavy industrial applications, such as elevators and cranes, initial commissioning tests are performed with the rotor locked. To compensate for errors in the current-scaling gain, the proposed method controls the current in the d-q axis using two-phase current-sensing methods in a stationary reference frame. The three-phase scaling gains are then estimated using the resulting d-axis current command and output voltage and are compensated for using these estimations. The proposed method delivers accurate compensations by considering the inequality between phase resistances. The effectiveness of the proposed algorithm is verified through simulations and experiments.

Study on the Fire Risk in Locked-Rotor Condition of Single-Phase Induction Motor

In this paper, the fire risk of a single-phase induction motor under a locked-rotor condition is described. In general, motor failure occurs in the locked-rotor condition owing to poor rotation of the rotor. Large inrush current flows when a motor starts, which is approximately 2–15 times larger than the rated current. In a single-phase induction motor under the locked-rotor condition, a large current that corresponds to the inrush current flows continuously through the stator winding. Such an overcurrent rises the temperature inside the stator winding, and thus the insulating material may catch fire. In this study, the restrained operating condition of the single-phase induction motor was simulated. Further, the degree of the overcurrent and temperature rise in the stator winding was measured. The experimental results, confirmed that the overcurrent was seven times larger than the rated current and the fire commenced at a temperature of approximately 300 ℃ inside the stator winding.

Design and Selection of Innovative Primary Circulation Pumps for GEN-IV Lead Fast Reactors

Although Lead-cooled Fast Reactor (LFR) is not a new concept, it continues to be an example of innovation in the nuclear field. Recently, there has been strong interest in liquid lead (Pb) or liquid lead–bismuth eutectic (LBE) both critical and subcritical systems in a relevant number of Countries, including studies performed in the frame of GENERATION-IV initiative. In this paper, the theoretical and computational findings for three different designs of Primary Circulation Pump (PCP) evolving liquid lead (namely the jet pump, the Archimedean pump and the blade pump) are presented with reference to the ALFRED (Advanced Lead Fast Reactor European Demonstrator) design. The pumps are first analyzed from the theoretical point of view and then modeled with a 3D CFD code. Required design performance of the pumps are approximatively around an effective head of 2 bar with a mass flow rate of 5000 kg/s. Taking into account the geometrical constraints of the reactor and the fluid dynamics characteristics of the molten lead, the maximum design velocity for molten lead fluid flow of 2 m/s may be exceeded giving rise to unacceptable erosion phenomena of the blade or rotating component of the primary pumping system. For this reason a deep investigation of non-conventional axial pumps has been performed. The results presented shows that the design of the jet pump looks like beyond the current technological feasibility while, once the mechanical challenges of the Archimedean (screw) pump and the fluid-dynamic issues of the blade pump will be addressed, both could represent viable solutions as PCP for ALFRED. Particularly, the blade pump shows the best performance in terms of pressure head generated in normal operation conditions as well as pressure drop in locked rotor conditions. Further optimizations (mainly for what the geometrical configuration is concerned) are still necessary.

Experimental Validation of 3-D Magnet Eddy Current Loss Prediction in Surface-Mounted Permanent Magnet Machines

This paper presents the experimental validation of three-dimensional (3-D) Fourier method employed for predicting magnet eddy current loss in surface-mounted permanent magnet (SPM) machines. The magnet loss is measured for a 12-slot 14-pole SPM machine from experimental tests when the machine is operated with inverter under locked rotor conditions by repeating tests with two rotors, one with magnets and one without. The eddy current loss associated with each significant harmonic in the captured armature currents is predicted separately employing the developed method and the total magnet loss is evaluated by applying the principle of superposition. The magnet loss at real operating conditions of the machine is predicted from the method using the phase current captured when the SPM is operating at its maximum speed conditions. The result is used as an example to devise an effective means of further reduction in the total magnet loss.

EXPERIMENTAL AND ANALYTICAL INVESTIGATION ON EFFECT OF STATOR WINDING TYPE TO EQUIVALENT CIRCUIT PARAMETERS OF INDUCTION MOTORS

Because of development in technology, the design of electrical machinery is changing. Induction motors, mostly used as electrical equipment, have developed over the years. One analytically studied area is the stator winding. Generally, each manufacturer uses techniques that directly affect the power of motors and thus, motor efficiency. In this study, the effects of three different stator winding types on motor parameters are investigated. Experiments are performed under no-load, load, and locked rotor conditions. Terminal voltage, power per phase, and phase current values are measured. Power and certain parameters are calculated using an equivalent circuit model. Lastly, a comparison of the results is provided.

Comparison of Protection Requirements in IE2-, IE3-, and IE4-Class Motors

In this paper, an overview of the main motor features influencing the protection devices settings is presented, pointing out key differences between three-phase direct-on-line (DOL) motors of different efficiency classes. The results of experimental tests and simulations are presented and discussed in the scope of the motor protection against overload, short-circuit, current unbalance, and locked-rotor conditions, for 7.5-kW, four-pole, IE2- and IE3-class squirrel-cage induction motors (SCIMs) and for IE4-class line-start permanent-magnet motors (LSPMs), offering important data related to their electrical and thermal behaviors. Two commercial digital thermal-magnetic motor protection devices, whose thermal models were designed for IE1- and IE2-class motors, are evaluated in terms of operation effectiveness in the tested motors. This paper is important for industry due to the significant penetration of IE3-class induction motors, as well as to the recent introduction into the market of IE4-class induction motors and LSPMs.

Determination of Parameters of Equivalent Circuit Taking No-Load Losses Into Account for Single-Phase Induction Motors

This paper proposes a step-by-step method of determining the parameters of equivalent circuit which is considered the no load losses for the single phase induction motor which has the starting winding. This method is comprised of three steps, and the stator resistance which is measured by the method of voltage drop is treated as constant and the stator and the rotor leakage reactances are assumed to be the same in every step. The test results of no load and locked rotor test are used in the 1st and 2nd step, and the ratings of name plate of the motor are needed in the 3rd step. In the 1st step, the traditional equivalent circuit parameters are directly calculated by no load and locked rotor conditions. In the next step, five nonlinear simultaneous equations for five unknown parameters can be set up by no load and locked rotor equivalent circuits. These equations are solved by using the initial parameters obtained by the 1st step parameters. In the final step, three nonlinear simultaneous equations for rotor winding resistance, leakage reactance and no load losses component resistance can be set up by equivalent circuit under the rated operation. Three parameters are solved by using the 2nd step parameters. Thus, equivalent circuit parameters are gradually refined step by step. The validity of the proposed method is evaluated by comparing the computed values obtained by the equivalent circuit parameters with the experimental values of the load test.

Optimization of the Performance of Single-Phase Capacitor-Run Induction Motor

The aim of the study was to suggest optimal solution for the impact of harmonics on the performance of Capacitor-Run Motor (CRM), the most commonly used single-phase motor. Therefore, investigations were carried out over the entire slip from no-load condition up to the locked-rotor condition, for harmonics of various orders in the case of using Pulse-Width Modulation (PWM) speed control. The investigations gave the ability to optimize the performance of CRM by choosing the appropriate parameters of the PWM inverter. Mathematical model for CRM supplied from voltage source contained harmonics was presented. The work was conducted by using a digital computer simulation (MATLAB software).

A study on the irreversible magnet demagnetization in single-phase line-start permanent magnet motor

The large demagnetizing currents in a single-phase line-start permanent magnet motor are generated by a starting and locked rotor condition. Thus, irreversible magnet demagnetization occurs due to the external demagnetizing field by these currents. In this paper, we present the phenomenon of the irreversible magnet demagnetization using two-dimensional finite-element method (2-D FEM). The nonlinear analysis of a permanent magnet is added to 2-D FEM to consider irreversible demagnetization. As a result, design techniques which are effective in avoiding irreversible demagnetization are proposed.

Development of a pump performance model for an integral effect test facility

Modeling methods for the reactor coolant pumps of the existing integral facilities are reviewed from the viewpoint of scaling, single- and two-phase characteristics. A series of separate effect tests was performed for the pumps of the ATLAS (Advanced Thermal-hydraulic test Loop for Accident Simulation) in order to obtain a complete set of single-phase homologous curves in all the quadrant operating regions. Besides the friction loss tests for the sheared shaft and the locked rotor conditions were conducted to extend the homologous curves to the limiting cases. A method which can take into account the two-phase degradation effects of the ATLAS pumps was suggested as a first approximation based on similarity principles. The present data and model can completely replace the pump input model of the MARS 3.1 code both for single- and two-phase conditions.

3D eddy current FE analysis of electromechanical devices

Presents the use of a 3D eddy current FE procedure for the analysis and design of two different induction machine structures: a radial and an axial machine. In the first case, attention is devoted to the simulation of locked rotor conditions and a linear 3D time harmonic eddy current FE analysis has been employed. The obtained results have been compared to 2D analysis and experimental data. The axial flux machine is analyzed under fixed speed conditions and a 3D time‐stepping and velocity eddy current problems are solved to evaluate machine performances. Different design configurations are analyzed in order to define the best solution.

Application of a sliding-mode observer for position and speed estimation in switched reluctance motor drives

A sliding-mode observer is applied toward the operation of a switched reluctance motor (SRM) drive. The sliding-mode observer estimates rotor position and velocity to control the conduction angles of the machine. Conventional on-off control with hysteresis current control is included with the position estimation scheme. The particular case of an automotive brake system motor is considered in detail where the conduction angles are modified with velocity feedback to provide optimum time response to brake system commands. Nonlinear modeling of a SRM is described and a computer simulation is developed based on data from an experimental SRM system. The sliding-mode observer is implemented with fixed-point and floating-point digital signal processors (DSPs) and the discrete-time implementations first examined under locked-rotor conditions. A comparison is also made between the implementation in two different types of DSPs. After confirming the accuracy of the computer simulation with experimental data, the design considerations in selecting observer coefficients with regard to sampling time, convergence rate, and transient stability are discussed. In conclusion, the effects of flux estimation errors on the system time response during a startup transient are examined.

A simple and robust adaptive controller for detuning correction in field-oriented induction machines

A novel adaptive controller for correcting the rotor time constant estimate used in the slip frequency calculator of indirect field-oriented controllers (IFOCs) is presented. The controller possesses near digital deadbeat performance and simultaneously maintains its correctness down to zero speed. The robust controller dynamics are based on an operating-point form of digital deadbeat control. The correctness down to zero rotor speed is based on the determination of the rotor flux from an accurate air-gap flux estimate obtained from the third harmonic stator phase voltage component introduced by the saturation of the machine stator teeth. The proposed controller is implemented using a digital signal processor, and the experimental results demonstrate its excellent performance for a wide range of rotor speeds, including locked rotor conditions. >

Magneto-thermal coupled analysis of canned induction motor

The authors present the calculation of the distribution of the transient temperature in the rotor bars of a canned induction motor, during locked rotor conditions, where the phenomena of electromagnetically induced currents and heat transfer are coupled. They have developed a coupled finite element electromagnetic code called WEMAP in which the calculated power loss densities are used as the heat sources for a transient thermal solution in subregions of the original problem geometry. These subregions are enclosed by surfaces on which either temperature or a convection boundary condition is known. In addition, the change in rotor bar resistance as a function of the temperature is included in these calculations. The calculated temperatures are compared with test results, and favorable agreement is obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Nonlinear analysis of a permanent magnet synchronous machine with nonsinusoidal stator winding currents

Permanent magnet synchronous machines and induction motors are often required to operate on-line starting or inverter-fed systems, which results in nonsinusoidal stator currents. These, in turn, give rise to undesirable harmonics and power losses which degrade motor performance. In this paper a time-domain analysis is presented for evaluating the magnetic field distribution in the two-dimensional cross section of the machine under load conditions. The analysis is applied to a permanent magnet synchronous machine under locked rotor conditions. Although for purposes of this analysis, the iron permeability has been assumed a constant, the method can be easily extended to include iron saturation.

Sensor Retrofitting of Motors For Protection Against Overtemperature

Low-cost fast-response thermal sensors are making it possible to add overtemperature protection to industrial motors on a retrofit basis. Easily applied by regular maintenance personnel, this protection system offers industrial plants, large and small, the opportunity for longer, trouble-free motor life, The application of sensors to existing induction motors to prevent thermal damage resulting from abnormal running overload or locked rotor conditions is also described here. Basic considerations for proper application are discussed, including motor winding configurations, insulation classes, and other design characteristics. Motor rewind shops provide a basic area of application where the sensors can be integrally installed in the stator winding at the time of repair. Examples and experiences are discussed where applications have been made.

Inherent-overheating protection

INHERENT-OVERHEATING protection is, as the name implies, protection based upon the actual motor temperature; thus, the motor is protected on the basis of total temperature and not temperature rise, as is the case when an external current-limiting device is used. Fundamentally, in order to realize true inherent-overheating protection, the temperature of the thermal element should follow at all times the motor-winding temperature, thus limiting the winding to a definite temperature, regardless of conditions of line voltage, motor load, ambient temperature, or ventilation. A common location for the thermostat is in the motor end shield, where it is in as close heat-receiving relationship to the stator windings as practicable. An auxiliary heater is provided in the thermostat to compensate for the difference in temperature between the stator copper and the thermostat mounting and to provide fast tripping under locked-rotor conditions. The auxiliary heater maintains the disk at a temperature somewhat above its ambient temperature; thus, the tripping characteristics of the disk-type thermostat are affected in a predetermined way by the ambient temperature of the thermal element.

Motor overload protectors on shipboard

At the present time, the bureau of Ships uses separately mounted-magnetically or thermally-actuated relays to protect a-c motors from overload, single-phase, and locked rotor conditions. With the advent of silicone-insulated motors requiring different overload relay characteristics, the development of relays operating on the actual motor winding temperature was undertaken.