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1. |
Record Nr. |
UNINA9910838224303321 |
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Autore |
Márquez Benjamin |
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Titolo |
The politics of patronage : lawyers, philanthropy, and the Mexican American legal defense and educational fund |
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Pubbl/distr/stampa |
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Austin : , : University of Texas Press, , 2021 |
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©2021 |
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ISBN |
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1-4773-2331-7 |
1-4773-2330-9 |
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Edizione |
[First edition.] |
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Descrizione fisica |
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1 online resource (184 pages) |
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Disciplina |
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Soggetti |
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Latin Americans - Political activity |
Mexican Americans - Political activity |
HISTORY / General |
History |
Electronic books. |
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Lingua di pubblicazione |
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Formato |
Materiale a stampa |
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Livello bibliografico |
Monografia |
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Nota di bibliografia |
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Includes bibliographical references and index. |
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Nota di contenuto |
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Cause lawyers, foundations and social movements -- A legal defense fund for Mexican Americans -- The Chicano movement -- Building a better organization -- The docket -- Conclusion. |
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Sommario/riassunto |
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Founded in 1968, the Mexican American Legal Defense and Educational Fund (MALDEF) is the Latino equivalent to the NAACP: a source of legal defense for the Latina/o community in cases centered on education, state immigration laws, redistricting, employment discrimination, and immigrant rights. Unlike the NAACP, however, MALDEF was founded by Mexican American activists in conjunction with the larger philanthropic structure of the Ford Foundation?a relationship that has opened it up to controversy and criticism. In the first book to examine this little-known but highly influential organization, Benjamin M?rquez explores MALDEF?s history and shows how it has thrived and served as a voice for the Latina/o community throughout its six decades of operation. But he also looks closely at large-scale investments of the Ford Foundation, Rockefeller Foundation, and others, considering how their ties to MALDEF have influenced Mexican American and Latinx politics. |
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Its story crafted from copious research into MALDEF and its benefactors, this book brings to light the influence of outside funding on the articulation of minority identities and the problems that come with creating change through institutional means. |
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2. |
Record Nr. |
UNINA9911006916503321 |
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Autore |
Hughes Austin |
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Titolo |
Electric motors and drives : fundamentals, types and applications / / Austin Hughes, Bill Drury |
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Pubbl/distr/stampa |
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Oxford, United Kingdom : , : Newnes, an imprint of Elsevier, , [2019] |
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©2019 |
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ISBN |
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Edizione |
[Fifth edition.] |
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Descrizione fisica |
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1 online resource (514 pages) |
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Disciplina |
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Soggetti |
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Control elèctric |
Motors elèctrics |
Electric driving |
Electric motors |
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Lingua di pubblicazione |
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Formato |
Materiale a stampa |
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Livello bibliografico |
Monografia |
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Nota di contenuto |
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Front Cover -- Electric Motors and Drives: Fundamentals, Types and Applications -- Copyright -- Contents -- Preface -- Chapter 1: Electric motors-The basics -- 1.1. Introduction -- 1.2. Producing rotation -- 1.2.1. Magnetic field and magnetic flux -- 1.2.2. Magnetic flux density -- 1.2.3. Force on a conductor -- 1.3. Magnetic circuits -- 1.3.1. Magnetomotive force (m.m.f.) -- 1.3.2. Electric circuit analogy -- 1.3.3. The air-gap -- 1.3.4. Reluctance and air-gap flux densities -- 1.3.5. Saturation -- 1.3.6. Magnetic circuits in motors -- 1.4. Torque production -- 1.4.1. Magnitude of torque -- 1.4.2. The beauty of slotting -- 1.5. Torque and motor volume -- 1.5.1. Specific loadings -- 1.5.2. Torque and rotor volume -- 1.5.3. Output power-Importance of speed -- 1.5.4. Power density (specific output power) -- 1.6. Energy conversion-Motional e.m.f -- 1.6.1. Elementary motor-Stationary |
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conditions -- 1.6.2. Power relationships-Conductor moving at constant speed -- 1.7. Equivalent circuit -- 1.7.1. Motoring and generating -- 1.8. Constant voltage operation -- 1.8.1. Behaviour with no mechanical load -- 1.8.2. Behaviour with a mechanical load -- 1.8.3. Relative magnitudes of V and E, and efficiency -- 1.8.4. Analysis of primitive machine-Conclusions -- 1.9. General properties of electric motors -- 1.9.1. Operating temperature and cooling -- 1.9.2. Torque per unit volume -- 1.9.3. Power per unit volume and efficiency-Importance of speed -- 1.9.4. Size effects-Specific torque and efficiency -- 1.9.5. Rated voltage -- 1.9.6. Short-term overload -- 1.10. Review questions -- Chapter 2: Power electronic converters for motor drives -- 2.1. Introduction -- 2.1.1. General arrangement of drive -- 2.2. Voltage control-D.C. output from d.c. supply -- 2.2.1. Switching control -- 2.2.2. Transistor chopper -- 2.2.3. Chopper with inductive load-Overvoltage protection. |
2.2.4. Boost converter -- 2.3. D.C. from a.c.-Controlled rectification -- 2.3.1. The thyristor -- 2.3.2. Single pulse rectifier -- 2.3.3. Single-phase fully-controlled converter-Output voltage and control -- Resistive load -- Inductive (motor) load -- 2.3.4. Three-phase fully-controlled converter -- 2.3.5. Output voltage range -- 2.3.6. Firing circuits -- 2.4. A.C. from d.c.-Inversion -- 2.4.1. Single-phase inverter -- 2.4.2. Output voltage control -- Mode A -- Mode B -- Mode C -- Mode D -- 2.4.3. Three-phase inverter -- 2.4.4. Multi-level inverter -- 2.4.5. Braking -- 2.4.6. Active front end -- 2.5. A.C. from a.c. -- 2.5.1. The cycloconverter -- 2.5.2. The matrix converter -- 2.6. Inverter switching devices -- 2.6.1. Bipolar junction transistor (BJT) -- 2.6.2. Metal oxide semiconductor field effect transistor (MOSFET) -- 2.6.3. Insulated gate bipolar transistor (IGBT) -- 2.7. Converter waveforms, acoustic noise, and cooling -- 2.7.1. Cooling of switching devices-Thermal resistance -- 2.7.2. Arrangement of heatsinks and forced-air cooling -- 2.8. Review questions -- Chapter 3: D.C. motors -- 3.1. Introduction -- 3.2. Torque production -- 3.2.1. Function of the commutator -- 3.2.2. Operation of the commutator-interpoles -- 3.3. Motional e.m.f. -- 3.3.1. Equivalent circuit -- 3.4. D.C. motor-steady-state characteristics -- 3.4.1. No-load speed -- 3.4.2. Performance calculation-example -- 3.4.3. Behaviour when loaded -- 3.4.4. Base speed and field weakening -- 3.4.5. Armature reaction -- 3.4.6. Maximum output power -- 3.5. Transient behaviour -- 3.5.1. Dynamic behaviour and time-constants -- 3.6. Four quadrant operation and regenerative braking -- 3.6.1. Full speed regenerative reversal -- 3.6.2. Dynamic braking -- 3.7. Shunt and series motors -- 3.7.1. Shunt motor-steady-state operating characteristics. |
3.7.2. Series motor-steady-state operating characteristics -- 3.7.3. Universal motors -- 3.8. Self-excited d.c. machine -- 3.9. Toy motors -- 3.10. Review questions -- Chapter 4: D.C. motor drives -- 4.1. Introduction -- 4.2. Thyristor d.c. drives-general -- 4.2.1. Motor operation with converter supply -- 4.2.2. Motor current waveforms -- 4.2.3. Discontinuous current -- 4.2.4. Converter output impedance: Overlap -- 4.2.5. Four-quadrant operation and inversion -- 4.2.6. Single-converter reversing drives -- 4.2.7. Double-converter reversing drives -- 4.2.8. Power factor and supply effects -- 4.3. Control arrangements for d.c. drives -- 4.3.1. Current limits and protection -- 4.3.2. Torque control -- 4.3.3. Speed control -- 4.3.4. Overall operating region -- 4.3.5. Armature voltage feedback and IR compensation -- 4.3.6. Drives without current control -- 4.4. Chopper-fed d.c. motor drives -- 4.4.1. Performance of chopper-fed d.c. motor drives -- 4.4.2. Torque-speed characteristics and control arrangements -- 4.5. D.C. servo drives -- 4.5.1. Servo motors -- 4.5.2. |
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Position control -- 4.6. Digitally-controlled drives -- 4.7. Review questions -- Chapter 5: Induction motors-Rotating field, slip and torque -- 5.1. Introduction -- 5.1.1. Outline of approach -- 5.2. The rotating magnetic field -- 5.2.1. Production of a rotating magnetic field -- 5.2.2. Field produced by each phase-winding -- 5.2.3. Resultant three-phase field -- 5.2.4. Direction of rotation -- 5.2.5. Main (air-gap) flux and leakage flux -- 5.2.6. Magnitude of rotating flux wave -- 5.2.7. Excitation power and VA -- 5.2.8. Summary -- 5.3. Torque production -- 5.3.1. Rotor construction -- 5.3.2. Slip -- 5.3.3. Rotor induced e.m.f. and current -- 5.3.4. Torque -- 5.3.5. Rotor currents and torque-small slip -- 5.3.6. Rotor currents and torque-large slip -- 5.3.7. Generating-Negative slip. |
5.4. Influence of rotor current on flux -- 5.4.1. Reduction of flux by rotor current -- 5.5. Stator current-speed characteristics -- 5.6. Review questions -- Chapter 6: Induction motor-Operation from 50/60Hz supply -- 6.1. Introduction -- 6.2. Methods of starting cage motors -- 6.2.1. Direct starting-Problems -- 6.2.2. Star/delta (wye/mesh) starter -- 6.2.3. Autotransformer starter -- 6.2.4. Resistance or reactance starter -- 6.2.5. Solid-state soft starting -- 6.2.6. Starting using a variable-frequency inverter -- 6.3. Run-up and stable operating regions -- 6.3.1. Harmonic effects-Skewing -- 6.3.2. High inertia loads-Overheating -- 6.3.3. Steady-state rotor losses and efficiency -- 6.3.4. Steady-state stability-Pull-out torque and stalling -- 6.4. Torque-speed curves-Influence of rotor parameters -- 6.4.1. Cage rotor -- 6.4.2. Double cage and deep bar rotors -- 6.4.3. Starting and run-up of slipring motors -- 6.5. Influence of supply voltage on torque-speed curve -- 6.6. Generating -- 6.6.1. Generating region -- 6.6.2. Self-excited induction generator -- 6.6.3. Doubly-fed induction machine for wind power generation -- 6.7. Braking -- 6.7.1. Plug reversal and plug braking -- 6.7.2. Injection braking -- 6.8. Speed control (without varying the stator supply frequency) -- 6.8.1. Pole-changing motors -- 6.8.2. Voltage control of high-resistance cage motors -- 6.8.3. Speed control of wound-rotor motors -- 6.8.4. Slip energy recovery -- 6.9. Power-factor control and energy optimisation -- 6.10. Single-phase induction motors -- 6.10.1. Principle of operation -- 6.10.2. Capacitor run motors -- 6.10.3. Split-phase motors -- 6.10.4. Shaded pole motors -- 6.11. Power range -- 6.11.1. Scaling down-The excitation problem -- 6.12. Review questions -- Chapter 7: Variable frequency operation of induction motors -- 7.1. Introduction. |
7.2. Variable frequency operation -- 7.2.1. Steady-state operation-Importance of achieving full flux -- 7.2.2. Torque-speed characteristics -- 7.2.3. Limitations imposed by the inverter-Constant torque and constant power regions -- 7.2.4. Limitations imposed by the motor -- 7.2.5. Four quadrant capability -- 7.3. Practical aspects of inverter-fed drives -- 7.3.1. PWM voltage source inverter -- 7.3.2. Current source induction motor drives -- 7.3.3. Performance of inverter-fed drives -- Open-loop (without speed/position feedback) induction motor drives -- Closed-loop (with speed/position feedback) induction motor drives -- Applications when field orientation or Direct Torque Control cannot be used -- 7.4. Effect of inverter on the induction motor -- 7.4.1. Acoustic noise -- 7.4.2. Motor insulation and the impact of long inverter-motor cables -- 7.4.3. Losses and impact on motor rating -- 7.4.4. Bearing currents -- 7.4.5. `Inverter grade induction motors -- 7.5. Utility supply effects -- 7.5.1. Harmonic currents -- 7.5.2. Power factor -- 7.6. Inverter and motor protection -- 7.7. Review questions -- Chapter 8: Field oriented control of induction motors -- 8.1. Introduction -- 8.2. Essential preliminaries -- 8.2.1. Space phasor |
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representation of m.m.f. waves -- 8.2.2. Transformation of reference frames -- 8.2.3. Transient and steady-states in electric circuits -- 8.3. Circuit modelling of the induction motor -- 8.3.1. Coupled circuits, induced EMF, and flux linkage -- 8.3.2. Self and mutual inductance -- 8.3.3. Obtaining torque from a circuit model -- 8.3.4. Finding the rotor currents -- 8.4. Steady-state torque under current-fed conditions -- 8.4.1. Torque vs slip frequency-Constant stator current -- 8.4.2. Torque vs slip frequency-Constant rotor flux linkage -- 8.4.3. Flux and torque components of stator current -- 8.5. Dynamic torque control. |
8.5.1. Special property of closely-coupled circuits. |
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Sommario/riassunto |
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Electric Motors and Drives: Fundamentals, Types and Applications, Fifth Edition is intended primarily for non-specialist users or students of electric motors and drives, but many researchers and specialist industrialists have also acknowledged its value in providing a clear understanding of the fundamentals. It bridges the gap between specialist textbooks (too analytical for the average user) and handbooks (full of detail but with little insight) providing an understanding of how each motor and drive system works. The fifth edition has been completely revised, updated and expanded. All of the most important types of motor and drive are covered, including d.c., induction, synchronous (including synchronous reluctance and salient Permanent Magnet), switched reluctance, and stepping. There has been significant innovation in this area since the fourth edition, particularly in the automotive, aircraft and industrial sectors, with novel motor topologies emerging, including hybrid designs that combine permanent magnet and reluctance effects. We now include a physical basis for understanding and quantifying torque production in these machines, and this leads to simple pictures that illuminate the control conditions required to optimise torque. The key converter topologies have been brought together, and the treatment of inverter switching strategies expanded. A new chapter is devoted to the treatment of Field Oriented control, reflecting its increasing importance for all a.c. motor drives. A unique physically-based approach is adopted which builds naturally on the understanding of motor behaviour developed earlier in the book: the largely non-mathematical treatment dispels much of the mystique surrounding what is often regarded as a difficult topic. Helps users acquire knowledge and understanding of the capabilities and limitations of motors and drives without struggling through unnecessary math and theory Presents updated material on the latest and most widely-used motors and drives, including brushless servo motors Includes additional diagrams and worked examples throughout this updated edition Includes a physical basis for the understanding and quantifying torque production |
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