Performance and torque-ripple characterization in induction motoradjustable-speed drives using time-stepping coupled finite-elementstate-space techniques

In this paper, the time-stepping coupled finite-element state-space (TSCFE-SS) model developed in an earlier companion paper is applied here for assessments of effects of machine geometry and magnetic circuit design modifications, and effects of pulsewidth modulation (PWM) carrier frequency on performance characteristics of induction motor drives. Namely, this has been accomplished through analysis of developed torque profile ripples and harmonic spectra of mid-air-gap radial flux density waveforms of the case-study motor. Furthermore, consequent effects of design modifications pertaining to geometry and/or magnetic circuit modifications and PWM carrier frequency on ohmic and iron core losses are investigated. The investigation has been performed on a case-study motor, which is a Y-connected single-layer three-phase two-pole 1.2-hp 208-V squirrel-cage induction motor with 24 stator slots and a cage with 34 rotor bars     

Preparation,characterization, and lithographic applications of glycidyl methacrylate/methacrylic acid/t‐butyl‐4‐vinylphenyl carbonate terpolymers

At present, most negative working lithographic plates use organic solvents as a developing medium. These developers have the obvious disadvantages of toxicity, fire risk, and are more expensive than the aqueous developers. This work describes the synthesis and characterization of materials that have similar photoactive properties to existing materials, but are soluble in water or aqueous medium rather than organic solvents. These materials are terpolymers comprising of one sort of material to induce water solubility, such as methacrylic acid (MAA) and another material to give the photoactive response such as glycidyl methacrylate (GMA). The tertiary‐butyl‐4‐vinyl phenyl carbonate (t‐BOCVP) was added as a chemically amplifying agent. Various terpolymers were prepared via free‐radical solution polymerization, typically in methyl ethyl ketone (MEK). Crosslinking reaction was induced using mixed arylsulphonium hexafluoroantimonate (MAS+ ‐SbF) as a photogenerating acid. It was found that the films of the terpolymer containing 85 mol % of GMA unit with the addition of 5 mol % rather than 2 mol % of the t‐BOCVP in the feed ratio gave good acid resistance and good adhesion to the surface of the zinc plate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Coupled finite-element/state-space modeling of turbogenerators inthe abc frame of reference-the short-circuit and load cases includingsaturated parameters

In this paper, a coupled finite-element/state space modeling technique is applied in the determination of the steady-state parameters of a 733 MVA turbogenerator in the abc frame of reference. In this modeling environment, the forward rotor stepping-finite element procedure described in a companion paper is used to obtain the various machine self and mutual inductances under short-circuit and load conditions. A fourth-order state-space model of the armature and field winding flux linkages in the abc frame of reference is then used to obtain the next set of flux linkages and forcing function currents for the finite-element model. In this process, one iterates between the finite-element and state-space techniques until the terminal conditions converge to specified values. This method is applied to the determination of the short-circuit, and reduced- and rated-voltage load characteristics, and the corresponding machine inductances. The spatial harmonics of these inductances are analyzed via Fourier analysis to reveal the impact of machine geometry and stator-to-rotor relative motion, winding layout, magnetic saturation, and other effects. In the full-load infinite-bus case, it is found that, while the three-phase terminal voltages are pure sinusoidal waveforms, the steady-state armature phase currents are nonsinusoidal and contain a substantial amount of odd harmonics which cannot be obtained using the traditional two-axis analysis     

New aqueous base developable photoresist for lithographic printing plates applications

Negative photoresists are materials that become insoluble in developing solution when exposed to optical radiation. This work describes the production of simple negative‐working resists, demonstrating aqueous development, for potential printing plate applications. The copolymers comprised glycidyl methacrylate (GMA) and acrylic acid (AA) via free‐radical solution polymerization in methyl ethyl ketone as a solvent using azobisisobutyronitrile as initiator at 60°C. Characterization of the copolymers prepared was carried out via IR, ¹H‐NMR, and thermal analysis techniques. The copolymers of GMA/AA were successfully prepared over a wide range of composition. It was found that the copolymer containing 15 mol % of AA unit in the feed was developed with NaOH on copper plate rather than zinc plate and crosslinked in the presence of photogenerated acid (PAG) caused by acid‐initiated ring‐opening polymerization of pendant epoxide groups. Exposure of the resist films to UV radiation at λ_max = 365 nm results in the generation of acid, and the subsequent baking process at 80°C for 1 min promotes the diffusion of the PAG, which initiates the cationic crosslinking of the epoxide rings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Induction machine broken-bar fault diagnosis using the rotor magnetic field space-vector orientation

A new technique based on rotor magnetic field space vector orientation is presented to diagnose broken-bar faults in induction machines operating at steady state. In this technique, stator currents and voltages are used as inputs to compute and subsequently observe the rotor magnetic field orientation, which has a more significant "swing-like" pendulous oscillation in case of broken-bar faults than in healthy operation. It will be shown here that the range of this "pendulous oscillation" is a function of the number of broken bars. Also in this technique, it was found that an inter-turn shorted stator-winding fault, which exhibits similar pendulous oscillation, could be distinguished from rotor broken-bar faults through the use of a variance index. In order to validate this method, experimental evidence is given here for several broken-bar cases in a 2-hp three-phase two-pole squirrel-cage induction machine.     

Diagnostics of bar and end-ring connector breakage faults inpolyphase induction motors through a novel dual track of time-seriesdata mining and time-stepping coupled FE-state space modeling

This paper develops the fundamental foundations of a technique for detection of faults in induction motors that is not based on the traditional Fourier transform frequency domain approach. The technique can extensively and economically characterize and predict faults from the induction machine adjustable speed drive design data. This is done through the development of dual-track proof-of-principle studies of fault simulation and identification. These studies are performed using our proven time stepping coupled finite element-state space method to generate fault case data. Then, the fault cases are classified by their inherent characteristics, so-called "signatures" or "fingerprints." These fault signatures are extracted or mined here from the fault case data using our novel time series data mining technique. The dual-track of generating fault data and mining fault signatures was tested here on three, six, and nine broken bar and broken end-ring connectors in a 208-volt, 60-Hz, 4-pole, 1.2-hp, squirrel cage 3-phase induction motor     

Comprehensive salient-pole synchronous machine parametric designanalysis using time-step finite element-state space modeling techniques

This paper details the application of a time-stepping coupled finite element-state space (CFE-SS) model to predict a salient-pole synchronous generator's parameters and performance, including damper bar current profiles and bar losses as well as iron core (including pole face) losses, under various operating conditions. The CFE-SS modeling environment is based on the natural ABC flux linkage frame of reference, which is coupled to a time/rotor stepping FE magnetic field and machine winding inductance profile computation model. This allows one to rigorously include the synergism between the space harmonics generated by magnetic saturation and machine magnetic circuit as well as winding layout topologies, and the time harmonics generated by the nonsinusoidal phase currents, ripple rich field excitation and damper bar currents. The impact of such synergism between these space and time harmonics on damper bar current profiles and losses, iron core losses, various machine winding current, voltage and torque profiles/waveforms is studied here for a 10-pole, 44.9 kVA, 17,143 RPM, 1428.6 Hz, 82 V (L-N), wound-pole aircraft generator     

Interturn Fault Diagnosis in Induction Motors Using the Pendulous Oscillation Phenomenon

A robust interturn fault diagnostic approach based on the concept of magnetic field pendulous oscillation, which occurs in induction motors under faulty conditions, is introduced in this paper. This approach enables one to distinguish and classify an unbalanced voltage power supply and machine manufacturing/construction imperfections from an interturn fault. The experimental results for the two case studies of a set of 5-hp and 2-hp induction motors verify the validity of the proposed approach. Moreover, it can be concluded from the experimental results that if the circulating current level in the shorted loop increases beyond the phase current level, an interturn fault can be easily detected using the proposed approach even in the presence of the existence of motor manufacturing imperfection effects     

Theoretical development and experimental verification of a DC-ACelectronically rectified load-generator system model compatible withcommon network analysis software packages

A method for modeling electronically commutated DC-AC load-rectifier-generator systems is presented. The method is based on a modified form of Park's d-q-o transformation, and yields an equivalent system network which is compatible with most commonly known network analysis software packages. The method was used to develop a model for the simulation of the dynamic steady-state performance of a DC-AC system consisting of a 30 kVA, three-phase, 208 V, four-pole, 400 Hz generator feeding a rectifier-load system. The system was tested in the laboratory under various DC and combined DC-AC load conditions. The results of the simulation model reveal a dynamic steady-state performance of the load-rectifier-generator system, in very good agreement with the test results. The applicability of the method and model to other electronically controlled machine systems is discussed in the light of those results     

Three-dimensional finite element analysis of permanent magnetbrushless DC motor drives-status of the state of the art

This paper reviews advances in the state of the art of applying three-dimensional finite-element (3-D-FE) magnetic field computation techniques to the analysis and quantification of parameters and performance of permanent magnet (PM) brushless DC motors as components of brushless DC drives. The application of the powerful 3-D-FE formulation based on the coupled magnetic vector potential-magnetic scalar potential (CMVP-MSP) concept to a case study PM brushless DC motor with skewed permanent magnet mounts is reviewed and summarized. This large-scale simulation of such a motor drive system is shown to be successfully implementable using workstation type computer environments