Electric Motors and Drives: Fundamentals, Types and Applications 3rd Revised edition

Electric Motors and Drives is intended for non-specialist users of electric motors and drives, filling the gap between academic textbooks (which are crammed with maths and theory not needed by most users) and the more prosaic 'handbooks' (which provide useful detail but little opportunity for the development of real insight and understanding). The book explores all of the widely-used modern types of motor and drive, including conventional and brushless D.C., induction motors (mains and inverter-fed), stepping motors, servo drives, synchronous motors (mains and converter-fed) and reluctance motors.

Austin Hughes' approach, using a minimum of maths, has established Electric Motors and Drives as a leading guide for electrical engineers and mechanical engineers, and the key to a complex subject for a wider readership, including technicians, managers and students.

The third edition includes additional diagrams and worked examples throughout. New topics include digital interfacing and control of drives, direct torque control of induction motors and current-fed operation in DC drives. The material on brushless servomotors has also been expanded.

* Acquire knowledge of and understanding of the capabilities and limitations of motors and drives without struggling through unnecessary maths and theory
* Updated material on the latest and most widely-used modern motors and drives, including brushless servomotors
* New edition includes additional diagrams and worked examples throughout

"Electric Motors and Drives" is intended for non-specialist users of electric motors and drives, filling the gap between maths- and theory-based academic textbooks and the more prosaic 'handbooks', which provide useful detail but little opportunity for the development of real insight and understanding. The book explores all of the widely-used modern types of motor and drive, including conventional and brushless D.C., induction motors and servo drives, providing readers with the knowledge to select the right technology for a given job. The third edition includes additional diagrams and worked examples throughout. New topics include digital interfacing and control of drives, direct torque control of induction motors and current-fed operation in DC drives. The material on brushless servomotors has also been expanded. Austin Hughes' approach, using a minimum of maths, has established Electric Motors and Drives as a leading guide for electrical engineers and mechanical engineers, and the key to a complex subject for a wider readership, including technicians, managers and students. The key features are: acquire knowledge of and understanding of the capabilities and limitations of motors and drives without struggling through unnecessary maths and theory; updated material on the latest and most widely-used modern motors and drives, including brushless servomotors; and new edition includes additional diagrams and worked examples throughout.

"This book is very readable, up-to-date and should be extremely useful to both users and o.e.m. designers. I unhesitatingly recommend it to any busy engineer who needs to make informed judgments about selecting the right drive system." - Drives and Controls "A very useful reference book for anyone wanting a comprehensive understanding of motors and drives ... I have not seen another book which covers this wide subject more comprehensively and in such an easy-to-read style." - Silicon Chip, May 2006 "I would regard this book as a light but broad coverage of many motor and drive concepts that have been around a long time." - Dennis Feucht, Innovatia.com "The coverage of drive types and behaviors is thorough and up to date." - Electrical Apparatus, May 2006

Preface		xvi
Electric Motors		1	(44)
Introduction		1	(1)
Producing Rotation		2	(5)
Magnetic field and magnetic flux		3	(1)
Magnetic flux density		4	(2)
Force on a conductor		6	(1)
Magnetic Circuits		7	(9)
Magnetomotive force (MMF)		9	(1)
Electric circuit analogy		10	(1)
The air-gap		11	(1)
Reluctance and air-gap flux densities		12	(2)
Saturation		14	(1)
Magnetic circuits in motors		15	(1)
Torque Production		16	(5)
Magnitude of torque		18	(1)
The beauty of slotting		19	(2)
Specific Loadings and Specific Output		21	(4)
Specific loadings		21	(2)
Torque and motor volume		23	(1)
Specific output power -- importance of speed		23	(2)
Energy Conversion -- Motional EMF		25	(5)
Elementary motor -- stationary conditions		26	(2)
Power relationships -- conductor moving at constant speed		28	(2)
Equivalent Circuit		30	(9)
Motoring condition		32	(1)
Behaviour with no mechanical load		32	(3)
Behaviour with a mechanical load		35	(2)
Relative magnitudes of V and E, and efficiency		37	(1)
Analysis of primitive motor -- conclusions		38	(1)
General Properties of Electric Motors		39	(3)
Operating temperature and cooling		39	(1)
Torque per unit volume		40	(1)
Power per unit volume -- importance of speed		41	(1)
Size effects -- specific torque and efficiency		41	(1)
Efficiency and speed		41	(1)
Rated voltage		41	(1)
Short-term overload		42	(1)
Review Questions		42	(3)
Power Electronic Converters for Motor Drives		45	(37)
Introduction		45	(2)
General arrangement of drives		45	(2)
Voltage Control -- D. C. Output from D.C. Supply		47	(8)
Switching control		48	(1)
Transistor chopper		49	(3)
Chopper with inductive load -- overvoltage protection		52	(2)
Features of power electronic converters		54	(1)
D.C. from A.C. -- Controlled Rectification		55	(10)
The thyristor		55	(1)
Single-pulse rectifier		56	(1)
Single-phase fully controlled converter -- output voltage and control		57	(5)
3-phase fully controlled converter		62	(2)
Output voltage range		64	(1)
Firing circuits		64	(1)
A.C. from D.C. SP -- SP Inversion		65	(7)
Single-phase inverter		65	(2)
Output voltage control		67	(1)
Sinusoidal PWM		68	(1)
3-phase inverter		69	(1)
Forced and natural commutation -- historical perspective		69	(1)
Matrix converters		70	(2)
Inverter Switching Devices		72	(3)
Bipolar junction transistor (BJT)		72	(1)
Metal oxide semiconductor field effect transistor (MOSFET)		73	(1)
Insulated gate bipolar transistor (IGBT)		74	(1)
Gate turn-off thyristor (GTO)		74	(1)
Converter Waveforms and Acoustic Noise		75	(1)
Cooling of Power Switching Devices		75	(4)
Thermal resistance		75	(2)
Arrangement of heatsinks and forced air cooling		77	(1)
Cooling fans		78	(1)
Review Questions		79	(3)
Conventional D.C. Motors		82	(51)
Introduction		82	(2)
Torque Production		84	(6)
Function of the commutator		86	(2)
Operation of the commutator -- interpoles		88	(2)
Motional E.M.F.		90	(5)
Equivalent circuit		94	(1)
D.C. motor -- Steady-State Characteristics		95	(12)
No-load speed		95	(1)
Performance calculation -- example		96	(2)
Behaviour when loaded		98	(5)
Base speed and field weakening		103	(2)
Armature reaction		105	(1)
Maximum output power		106	(1)
Transient Behaviour -- Current Surges		107	(4)
Dynamic behaviour and time-constants		108	(3)
Shunt, Series and Compound Motors		111	(8)
Shunt motor -- steady-state operating characteristics		113	(2)
Series motor -- steady-state operating characteristics		115	(3)
Universal motors		118	(1)
Compound motors		119	(1)
Four-Quadrant Operation and Regenerative Braking		119	(5)
Full speed regenerative reversal		122	(2)
Dynamic braking		124	(1)
Toy Motors		124	(2)
Review Questions		126	(7)
D.C. Motor Drives		133	(34)
Introduction		133	(1)
Thyristor D.C. Drives -- General		134	(14)
Motor operation with converter supply		136	(1)
Motor current waveforms		136	(3)
Discontinuous current		139	(2)
Converter output impedance: overlap		141	(2)
Four-quadrant operation and inversion		143	(1)
Single-converter reversing drives		144	(2)
Double SP-converter reversing drives		146	(1)
Power factor and supply effects		146	(2)
Control Arrangements for D.C. Drives		148	(7)
Current control		150	(2)
Torque control		152	(1)
Speed control		152	(2)
Overall operating region		154	(1)
Armature voltage feedback and IR compensation		155	(1)
Drives without current control		155	(1)
Chopper-Fed D.C. Motor Drives		155	(4)
Performance of chopper-fed d.c. motor drives		156	(3)
Torque-speed characteristics and control arrangements		159	(1)
D.C. Servo Drives		159	(4)
Servo motors		160	(2)
Position control		162	(1)
Digitally Controlled Drives		163	(1)
Review Questions		164	(3)
Induction Motors -- Rotating Field, Slip and Torque		167	(31)
Introduction		167	(3)
Outline of approach		168	(2)
The Rotating Magnetic Field		170	(13)
Production of rotating magnetic field		172	(1)
Field produced by each phase winding		172	(4)
Resultant field		176	(1)
Direction of rotation		177	(1)
Main (air-gap) flux and leakage flux		177	(2)
Magnitude of rotating flux wave		179	(3)
Excitation power and VA		182	(1)
Summary		183	(1)
Torque Production		183	(8)
Rotor construction		183	(2)
Slip		185	(1)
Rotor induced e.m.f., current and torque		185	(2)
Rotor currents and torque -- small slip		187	(2)
Rotor currents and torque -- large slip		189	(2)
Influence of Rotor Current on Flux		191	(2)
Reduction of flux by rotor current		192	(1)
Stator Current-Speed Characteristics		193	(3)
Review Questions		196	(2)
Operating Characteristics of Induction Motors		198	(38)
Methods of Starting Cage Motors		198	(8)
Direct Starting -- Problems		198	(4)
Star/delta (wye/mesh) starter		202	(1)
Autotransformer starter		202	(1)
Resistance or reactance starter		203	(1)
Solid-state soft starting		204	(2)
Starting using a variable-frequency inverter		206	(1)
Run-up and Stable Operating Regions		206	(5)
Harmonic effects -- skewing		208	(1)
High inertia loads -- overheating		209	(1)
Steady-state rotor losses and efficiency		209	(1)
Steady-state stability -- pullout torque and stalling		210	(1)
Torque-Speed Curves -- Influence of Rotor Parameters		211	(6)
Cage rotor		211	(2)
Double cage rotors		213	(1)
Deep bar rotors		214	(1)
Starting and run-up of slipring motors		215	(2)
Influence of Supply Voltage on Torque--Speed Curve		217	(1)
Generating and Braking		218	(3)
Generating region -- overhauling loads		219	(1)
Plug reversal and plug braking		220	(1)
Injection braking		221	(1)
Speed Control		221	(4)
Pole-changing motors		222	(1)
Voltage control of high-resistance cage motors		223	(1)
Speed control of wound-rotor motors		224	(1)
Power Factor Control and Energy Optimisation		225	(2)
Voltage control		225	(2)
Slip energy recovery (wound rotor motors)		227	(1)
Single-Phase Induction Motors		227	(5)
Principle of operation		227	(2)
Capacitor-run motors		229	(1)
Split-phase motors		230	(1)
Shaded-pole motors		231	(1)
Size Range		232	(1)
Scaling down -- the excitation problem		232	(1)
Review Questions		233	(3)
Induction Motor Equivalent Circuit		236	(43)
Introduction		236	(2)
Outline of approach		237	(1)
Similarity Between Induction Motor and Transformer		238	(2)
The Ideal Transformer		240	(8)
Ideal transformer -- no-load condition, flux and magnetising current		240	(5)
Ideal transformer -- no-load condition, voltage ratio		245	(1)
Ideal transformer on load		246	(2)
The Real Transformer		248	(10)
Real transformer -- no-load condition, flux and magnetising current		248	(3)
Real transformer -- leakage reactance		251	(1)
Real transformer on load -- exact equivalent circuit		252	(2)
Real transformer -- approximate equivalent circuit		254	(2)
Measurement of parameters		256	(1)
Significance of equivalent circuit parameters		257	(1)
Development of the Induction Motor Equivalent Circuit		258	(3)
Stationary conditions		258	(1)
Modelling the electromechanical energy conversion process		259	(2)
Properties of Induction Motors		261	(2)
Power balance		262	(1)
Torque		262	(1)
Performance Prediction -- Example		263	(4)
Line current		264	(1)
Output power		264	(1)
Efficiency		265	(1)
Phasor diagram		266	(1)
Approximate Equivalent Circuits		267	(7)
Starting and full-load relationships		268	(1)
Dependence of pull out torque on motor parameters		269	(1)
Analysis		270	(1)
Graphical interpretation via phasor diagram		271	(3)
Measurement of Parameters		274	(1)
Equivalent Circuit Under Variable-Frequency Conditions		274	(3)
Review Questions		277	(2)
Inverter-Fed Induction Motor Drives		279	(26)
Introduction		279	(7)
Comparison with d.c. drive		280	(2)
Inverter waveforms		282	(2)
Steady-state operation -- importance of achieving full flux		284	(2)
Torque--Speed Characteristics -- Constant Vlf Operation		286	(4)
Limitations imposed by the inverter -- constant power and constant torque regions		288	(1)
Limitations imposed by motor		289	(1)
Control Arrangements for Inverter-Fed Drives		290	(6)
Open-loop speed control		291	(2)
Closed-loop speed control		293	(3)
Vector (Field-Oriented) Control		296	(4)
Transient torque control		297	(3)
Cycloconverter Drives		300	(3)
Review Questions		303	(2)
Stepping Motors		305	(35)
Introduction		305	(6)
Open-loop position control		306	(1)
Generation of step pulses and motor response		307	(1)
High-speed running and ramping		308	(3)
Principle of Motor Operation		311	(7)
Variable reluctance motor		312	(2)
Hybrid motor		314	(3)
Summary		317	(1)
Motor Characteristics		318	(6)
Static torque--displacement curves		318	(1)
Single-stepping		319	(1)
Step position error and holding torque		320	(1)
Half stepping		321	(2)
Step division -- mini-stepping		323	(1)
Steady-State Characteristics -- Ideal (Constant-Current) Drive		324	(4)
Requirements of drive		324	(2)
Pull-out torque under constant-current conditions		326	(2)
Drive Circuits and Pull-Out Torque-Speed Curves		328	(7)
Constant-voltage drive		328	(2)
Current-forced drive		330	(1)
Chopper drive		331	(2)
Resonances and instability		333	(2)
Transient Performance		335	(3)
Step response		335	(1)
Starting from rest		336	(1)
Optimum acceleration and closed-loop control		337	(1)
Review Questions		338	(2)
Synchronous, Brushless D.C. and Switched Reluctance Drives		340	(26)
Introduction		340	(1)
Synchronous Motors		341	(11)
Excited-rotor motors		343	(1)
Equivalent circuit of excited-rotor synchronous motor		344	(3)
Phasor diagram and Power-factor control		347	(2)
Starting		349	(1)
Permanent magnet synchronous motors		350	(1)
Hysteresis motors		351	(1)
Reluctance motors		351	(1)
Controlled-Speed Synchronous Motor Drives		352	(5)
Open-loop inverter-fed synchronous motor drives		353	(1)
Self-synchronous (closed-loop) operation		354	(1)
Operating characteristics and control		355	(2)
Brushless D.C. Motors		357	(1)
Switched Reluctance Motor Drives		358	(5)
Principle of operation		359	(1)
Torque prediction and control		360	(3)
Power converter and overall drive characteristics		363	(1)
Review Questions		363	(3)
Motor/Drive Selection		366	(15)
Introduction		366	(1)
Power Range for Motors and Drives		366	(2)
Maximum speed and speed range		368	(7)
Load Requirements -- Torque-Speed Characteristics		369	(1)
Constant-torque load		369	(5)
Inertia matching		374	(1)
Fan and pump loads		374	(1)
General Application Considerations		375	(4)
Regenerative operation and braking		375	(1)
Duty cycle and rating		376	(1)
Enclosures and cooling		377	(1)
Dimensional standards		378	(1)
Supply interaction and harmonics		378	(1)
Review Questions		379	(2)
APPENDIX -- INTRODUCTION TO CLOSED-LOOP CONTROL		381	(19)
Reasons for Adopting a Simplified Approach		381	(1)
Closed-Loop (Feedback) Systems		382	(4)
Error-activated feedback systems		383	(1)
Closed-loop systems		384	(2)
Steady-State Analysis of Closed-Loop Systems		386	(4)
Importance of Loop Gain -- Example		390	(2)
Steady-State Error -- Integral Control		392	(2)
PID Controller		394	(2)
Stability		396	(1)
Disturbance Rejection -- Example Using D.C. Machine		397	(3)
Further Reading		400	(1)
Answers to Numerical Review Questions		401	(3)
Index		404