EBOOK điện ổ đĩa các nguyên tắc lập kế hoạch ứng dụng các giải pháp sách (jens weidauer) sách (jens weidauer)EBOOK điện ổ đĩa các nguyên tắc lập kế hoạch ứng dụng các giải pháp sách (jens weidauer)EBOOK điện ổ đĩa các nguyên tắc lập kế hoạch ứng dụng các giải pháp sách (jens weidauer)
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Trang 6Electrical drives are the most important source of mechanical energy in machinesand industrial plant In our modern world, they ensure that motion can take place,and that transport and manufacturing processes are possible at all Although thetechnical field of electrical drives is over 100 years old, today it is more dynamic anddiverse than ever
It starts with the electric motors themselves, the heart of all electrical drives Today,they are not only available in the widest range of designs and power classes – fromstandard motors for direct-on-line operation to highly-efficient servo motors – butthey also distinguish themselves through their ever more ingenious design princi-ples and use of novel materials Smaller, lighter, and more efficient electric motorsgive designers new degrees of freedom, pushing ahead the development of ma-chines, plant equipment, and electrical vehicles
Drive controllers are also becoming more powerful and smaller due to fast, low-lossswitching power semiconductors, faster microprocessors, as well as modern manu-facturing technologies In combination with innovative electrical motors, the torque,speed, and position of electrical drives can today, at any given time, be set exactly asrequired by the manufacturing or transport process In many instances, the control-ler and electric motor are brought together and combined in one device In particu-lar, electromobility is driving the development of real mechatronic systems, in whichgearbox, electric motor, and drive controller merge together to provide customiseddrive solutions
As part of a modern automation solution, electrical drives must be universally dinated To enable this, they are equipped with communication interfaces as well asintegrated control, safety, and diagnostic functions going well beyond those of theclassic drive controller These allow the planner to implement the required coordina-tion functions centrally, distributed, or in the drive itself
coor-Through both technical advancements and increasingly finer adaptations for specialrequirements, the wealth of types of electrical drives will continue to increase Goodorientation in the world of electrical drives is therefore indispensable for both deci-sion makers and designers This book provides this Both the principles as well as theapplication of electrical drives are presented systematically and clearly This compre-hensive overview will benefit the reader and provide added confidence when evaluat-ing drive solutions
Now in its third edition, this “standard work of electrical drives” will continue tobroaden the knowledge of electrical drives, and for many technicians be a usefulguide when designing efficient machines, plant equipment, and electrical vehicles
Prof Dr Siegfried Russwurm
Member of the Managing Board of Siemens AG
Trang 71 Electrical drives at a glance 12
1.1 A short history of electrical drives 12
1.2 Design of modern electrical drives 16
1.3 Classification of electrical drives 18
1.3.1 Speed variability 18
1.3.2 Motor and controller types 21
1.3.3 Technical data 22
2 Mechanical principles 26
3 Electrical principles 28
3.1 Fields in electrical engineering 28
3.2 Developing torque 30
3.2.1 Lorentz force 30
3.2.2 Current carrying loop in a magnetic field 31
3.2.3 Induced voltage 32
3.2.4 Quantities and equations of electrical engineering 33
3.2.5 Components of electrical engineering 34
4 Fixed-speed and variable-speed drives with DC motors 36
4.1 DC drives 36
4.2 The DC motor 37
4.2.1 Operating principle 37
4.2.2 Construction and electrical connections 42
4.2.3 DC motor maintenance 43
4.2.4 Mathematical description 44
4.2.5 Controllability 46
4.3 Fixed-speed drives using DC motors 47
4.3.1 Design and application 47
4.3.2 Shunt-wound characteristic 48
4.3.3 Series-wound characteristic 50
4.4 Variable-speed drives using DC motors 51
4.4.1 Design and application 51
4.4.2 Converter 53
4.4.3 Speed encoders for DC drives 59
4.4.4 Control structure 61
Trang 85 Fixed-speed and variable-speed drives with asynchronous motors 64
5.1 Drives with asynchronous motors 64
5.2 The asynchronous motor 65
5.2.1 Functional principle 65
5.2.2 Construction and electrical connections 68
5.2.3 Mathematical description 71
5.2.4 Controllability 76
5.3 Fixed-speed drives using asynchronous motors 77
5.3.1 Design and applications 77
5.3.2 Starting an asynchronous motor 79
5.3.3 Stopping an asynchronous motor 85
5.4 Variable-speed drives with asynchronous motors 85
5.4.1 Design and applications 85
5.4.2 Changing the speed using contactors 86
5.4.3 Speed changing using frequency converters 89
5.4.4 V/f control 96
5.4.5 Vector-control operation 99
5.4.6 Speed encoder 103
5.5 Modern frequency converter functions 107
5.5.1 General 107
5.5.2 Power options 107
5.5.3 Electronic options 109
5.5.4 Process interfaces 111
5.5.5 User interface 113
5.5.6 Open-loop and closed-loop functions 114
6 Servo drives 123
6.1 Design and application 123
6.2 Classification of servo drives 125
6.2.1 Control functions 125
6.2.2 Motor types, types of amplifier 126
6.2.3 Technical data 128
6.3 Speed and position encoders for servo drives 129
6.3.1 Classification and characteristics 129
6.3.2 Commutation encoder 133
6.3.3 Resolver 134
6.3.4 Sine/cosine encoder 137
6.3.5 Absolute encoder 139
6.4 Servo drives using DC motors 140
6.4.1 Design and application 140
6.4.2 DC motors for servo drives 140
6.4.3 Controllers for servo drives using DC motors 141
6.4.4 Control scheme 145
6.5 Servo drives with brushless DC motors (block commutation) 146
6.5.1 Design and applications 146
6.5.2 The brushless DC motor 147
6.5.3 Frequency converters for servo drives with brushless DC motors 149
6.5.4 Control scheme 151
Trang 96.6 Servo drives using synchronous motors (sinusoidal commutation) 152
6.6.1 Design and application 152
6.6.2 The synchronous motor 153
6.6.3 Frequency converters for servo drives with synchronous motors 155
6.6.4 Control scheme 155
6.7 Servo drives with asynchronous motors 157
6.8 Direct drives 158
6.8.1 Designs and applications 158
6.8.2 Linear motor 160
6.8.3 Torque motor 162
6.9 Control of and tuning servo drives 163
6.9.1 General quality criteria for evaluating control loops 163
6.9.2 Servo drive control loops 167
6.9.3 Tuning the current control loop 168
6.9.4 Tuning the speed control loop 171
6.9.5 Tuning the position control loop 175
6.10 Functions of modern servo amplifiers 177
6.10.1 General 177
6.10.2 Power options 178
6.10.3 Electronic options 178
6.10.4 Process interfaces 178
6.10.5 User interfaces 179
6.10.6 Closed-loop and open-loop control functions 179
7 Stepper drives 182
7.1 Designs and applications 182
7.2 Classification of stepper drives based upon motor type 183
7.3 Technical data 184
7.4 The stepper motor 185
7.4.1 General 185
7.4.2 Permanent magnet stepper motor 185
7.4.3 Hybrid stepper motor 187
7.5 Controllers 188
7.6 Control characteristics 192
8 Electrical drive systems at a glance 194
8.1 From drive to drive system 194
8.2 Classification of electrical drive systems 195
8.2.1 Components in a drive system 195
8.2.2 Functionality of drive systems 198
8.2.3 Information flow in drive systems 200
8.2.4 Energy flow between drives 202
8.2.5 Electromagnetic interference 203
8.3 Planning of electrical drives as a system task 203
Trang 109 Fieldbuses for electrical drives 204
9.1 Motivation and functional principle 204
9.2 Overview of fieldbuses in common use 208
9.3 AS-Interface 209
9.3.1 Overview 209
9.3.2 Topology, wiring, physics 210
9.3.3 Access method 213
9.4 CAN 213
9.4.1 Overview 213
9.4.2 Topology, wiring, physical interface 215
9.4.3 Access method 216
9.4.4 Engineering 218
9.5 PROFIBUS DP 218
9.5.1 Overview 218
9.5.2 Topology, wiring, physical interface 219
9.5.3 Access method 221
9.5.4 PROFIBUS DP-V2 223
9.5.5 Engineering 225
9.6 PROFINET I/O 228
9.6.1 Overview 228
9.6.2 Topology, wiring, physical interface 230
9.6.3 Access method 232
9.6.4 Device descriptions for engineering 237
10 Process control with electrical drives 238
10.1 Definition of terms 238
10.2 Process control with single drive systems 238
10.2.1 Components 238
10.2.2 Example: Level control with a fixed-speed drive 239
10.2.3 Example: Pressure control 241
10.2.4 Example: Elevator drive 243
10.3 Process control with multi-drive systems 245
10.3.1 Components 245
10.3.2 Example: Carriage with mechanically coupled drives 248
10.3.3 Example: Coating line with tension and winding drives 251
10.4 Drives with integrated technology functions 260
11 Motion control with electrical drives 263
11.1 Definition of terms and functions 263
11.2 Representing and processing position information 266
11.3 Positioning 269
11.3.1 Applications and fundamentals 269
11.3.2 Positioning controller 269
11.3.3 Machine data 274
11.3.4 Position detection, position processing and referencing 275
Trang 1111.4 Synchronisation 279
11.4.1 Applications and principles 279
11.4.2 Synchronisation control 280
11.4.3 Machine data 293
11.5 Motion control with PLCopen 293
11.6 Safety functions in electrical drives 296
11.6.1 Applications and principles 296
11.6.2 Safe stop functions 298
11.6.3 Safe movement functions 300
11.6.4 Safe fieldbuses 302
12 EMC and electrical drives 303
12.1 Principles 303
12.1.1 Background and definition of terms 303
12.1.2 EMC interference model 304
12.1.3 Coupling mechanisms 305
12.1.4 Mathematical description 310
12.2 Electrical drives as a source of interference 314
12.2.1 Galvanic disturbances generated by converter-fed DC drives, countermeasures 314
12.2.2 Galvanic disturbances generated by DC-link converters, countermeasures 317
12.2.3 Galvanic interference generated by the inverter, countermeasures 319
12.2.4 Radiated interference due to the inverter 325
12.2.5 Radiated interference arising from digital drives, countermeasures 327
12.3 Electrical drives as susceptible devices 328
12.3.1 General 328
12.3.2 Galvanic interference, countermeasures 328
12.3.3 Capacitive interference, countermeasures 330
12.3.4 Inductive interference, countermeasures 331
12.4 EMC guidelines 333
13 Planning electrical drives 335
13.1 Approach 335
13.2 Selecting the drive type 336
13.3 Selecting the motor 339
13.3.1 Approach 339
13.3.2 Taking a gearbox into consideration 339
13.3.3 Sizing the motor using mechanical parameters 345
13.3.4 Thermal sizing of the motor 351
13.3.5 Constructional motor selection 357
13.3.6 Selecting the encoder 361
13.4 Sizing the converter for variable-speed and servo drives 364
13.4.1 Electrical sizing of the converter 364
Trang 1213.4.2 Thermal sizing of the converter 364
13.4.3 Thermal sizing of the supply infeed 370
13.4.4 Sizing the supply infeed based on the DC link capacitance 373
13.4.5 Sizing the braking chopper and braking resistor 374
13.4.6 Selecting the power options 377
13.4.7 Electronic options, accessories, connecting cables 377
13.5 Planning example 378
13.5.1 Application data 378
13.5.2 Sizing 379
14 Troubleshooting electrical drives 383
14.1 Avoiding faults and troubleshooting 383
14.2 Possible faults and errors 383
14.2.1 Motor faults 385
14.2.2 Encoder faults 386
14.2.3 Faults in the controller 387
14.2.4 Supply faults 388
14.2.5 Communication errors 389
14.2.6 EMC problems 390
14.2.7 Planning errors 391
14.2.8 Parameter setting errors 392
14.3 Fault indication 393
Index 395
Trang 131.1 A short history of electrical drives
Electrical drives convert electrical energy into mechanical energy andserve as the intermediary between the electrical supply system, the en-ergy source, and the driven machine, the energy consumer
Due to their central position in the energy chain flow, electrical driveshave become a key component in industrial applications, as well as intransportation and in consumer goods In many areas, they have driventechnical development and have themselves been the focus of numer-ous developments
The core component of every electrical drive is the motor The physicallaws, upon which the motor is based, were discovered in the early 19th
nee-of the interaction between electrical currents and magnetic fields.These discoveries led to the development of a large number of “electro-magnetic machines”, whose practical application, however, were limit-
ed due to the limited source of electrical energy available at the time.Current was produced by galvanic cells, which prevented the use ofsuch “machines” They could not establish themselves against thesteam engine or the many types of gas or petrol driven engines
An important step was made in 1831 Michael Faraday discovered tromagnetic induction This effect was immediately put to use in gener-ators In 1866, Werner von Siemens invented the dynamo This direct
elec-Figure 1.1 Electrical drives as the intermediary between the electrical supply
system and the driven machine
Energy flow when motoring
Electrical supply
Electrical drive
Driven machine
Energy flow when generating
Trang 14current generator uses the magnetic remanence of the magnetic poles
to initially produce a small induced current This induced current is
then used to produce an excitation field, which in turn brings the
gen-erator up to full power Further development of these gengen-erators has
given us the modern day motor
Electrical power transmission
1875 to 1891
At the end of the 19th century, a central problem was supplying energy
in the small quantities required for machines in light industries Steam
engines were costly to maintain and for safety reasons could not be
used everywhere Gas powered motors were therefore in widespread
use Competition came from dynamo machines, which had been
con-tinuously developed and improved The arrangement consisted of two,
electrically connected dynamo machines One machine was used as a
generator, the other as a motor In this way, the electrical energy
re-quired could be generated at one location, transmitted over a longer
distance and then, at the location where it was required, be converted
back into mechanical energy Electrical energy replaced mechanical
en-ergy as the transmission medium The main applications were electric
locomotives and street cars but also machine drives, e.g for weaving
machines, were realised
In 1887, the term “electric motor” appeared for the first time in a sales
catalogue In 1891 the advantages of the electric motor over a steam
en-gine and gas motor were described as being:
• they do not need a fixed foundation, can be mounted in any position,
require little space, and can be used in domestic quarters
• they can be run at relatively high speeds, the speed and direction of
running can be altered, they have a favourable efficiency and are
easy to operate
Figure 1.2 Electric motor by Moritz Hermann Jacobi, 1818
Photograph: Deutsches Museum, Munich
Trang 15In 1889, Michael von Dolivo-Dobrowolski invented the three-phasesquirrel-cage induction motor It was he who coined the term three-phase electricity Additionally, in 1891 he realised the first three-phasepower transmission network, from Lauffen am Neckar to Frankfurt amMain, a distance of 175 km.
Figure 1.3 Froment’s electromagnetic “mouse mill” motor
(from Meyers Konversations-Lexikon 1886) Photograph: Deutsches Museum, Munich
Figure 1.4 Dynamo Siemens & Halske, 1877 supplied for the Oker iron works
Photograph: Deutsches Museum, Munich
Trang 16wide scale Electrical motors were continuously improved with regard
to their technical data and their starting characteristics With the use of
resistor networks and the Ward Leonard set (a converter for altering
the voltage and frequency), controllable electrical drives became
avail-able This led to the gradual replacement of steam engines and
trans-mission systems in workshops The machine design could now be
opti-mised to the needs of the manufacturing process and was no longer
subordinate to the supply of energy via transmission shafts
Electrical drives proliferate
1920 to 1950
From around 1920 onwards, electrical drives spread in to all areas of
in-dustry, farming, trade crafts, transportation, and into households
Typ-ical drive solutions consisted of DC or AC motors, which depending on
the application, were complemented with a controller for adjusting the
speed The number of electrical drives increased significantly Electrical
motors themselves developed in two directions: to integrated solutions
within the driven machine, and to standardised mass products The
asynchronous induction motor became the most widely used type in
in-dustrial applications In addition to contactor controls, the first
con-trollers, based on mercury-vapour rectifiers, were used for variable
speed applications Power electronics had found their way into
electri-cal drives
Converter drives
1950 to 1970
The development of power semiconductors was the beginning of the
end for the mercury-vapour rectifier In parallel, controllers based on
analogue electronic components were developed, which supported the
spread of variable-speed drives The simple controllability of DC drives
led to their resurgence
Drives with microprocessor since 1970
The introduction of the microprocessor led to a burst of development
in electrical drives Analogue controllers were replaced by digital ones
Their performance improved continuously, enabling more and more
complex functions to be implemented The development of the
“field-oriented control” method by Blaschke in 1971, and its subsequent
im-plementation in a processor-controlled digital drive, enabled AC
mo-tors to be controlled with the same control performance as a DC motor
Figure 1.5 Digital control board of
a DC drive
Figure 1.6 High power IGBT (Insulated Gate Bipolar
Transistor) as used in a frequency converter
Trang 17The availability of increasingly more powerful microprocessors enabledthe integration of functions originally foreign to the drive into the con-troller The boundaries between electrical drives and automation devic-
es have become less clearly defined Drive systems, which consist ofelectronically-coordinated low-power servo drives, are more and morereplacing centralised drives with mechanical gearboxes and main lineshafts
1.2 Design of modern electrical drives
The mechanical energy supplied by the electrical drive is used to trol the process variables in the driven machine The mechanical ener-
con-gy must be adjusted or switched on and off to the process needs Forthis reason, a modern electrical drive consists not only of an electricalmotor but also a host of additional components (see Figure 1.8)
ener-gy transformer, converting the electrical enerener-gy supplied to mechanicalenergy In generating operation, e.g when braking, the energy flow is
in the opposite direction: mechanical energy is then converted back
in-to electrical energy
quanti-ties such as rotary speed, speed, and position and makes these available
to the signal electronics
mo-tor from moving when the controller is switched off Particularly whenhandling suspended loads, e.g robotic arms, elevators, and hoists, thebrake holds the mechanical system tight even when the drive is inactive
Figure 1.7 Modern digital DC drive converter
Trang 18A gearbox is a mechanical transformer It matches the mechanical
quantities supplied by the motor such as speed and torque to those
re-quired by the driven machine
A further task is to convert the rotary motion of a motor into a linear
movement where necessary
Switchgear and protection equipment
Switchgear and protection equipment disconnect the electrical drive
from the supply when necessary and protect the drive and supply
ca-bles from overload Overloading can be caused by the driven machine
itself or be the result of a fault in the drive
Controller
A controller consists of a power section and signal electronics:
• the power section “portions” the electrical energy to the motor and
therefore influences the mechanical energy delivered by the motor
The power section of modern electrical drives is based on power
semiconductors These act as electrical switches, switching the flow
of electrical energy to the motor on and off Integrated measurement
systems measure the electrical currents and voltages and make these
available to the signal electronics
• the signal electronics is the “brain” of an electrical drive It
deter-mines the control signals for the power section so that the desired
power or movement is delivered at the motor shaft To enable this,
Figure 1.8 Functional blocks of a modern electrical drive
Driven machine
Motor Gearbox Brake
Motor encoder
Machine encoder
Supply
Signal electronics with
controller and monitoring
Higher-level controller
Current actual value
Controller
Electrical drive
Speed actual value
Position actual value
Trang 19the signal electronics has different control functions The requiredelectrical quantity actual values are supplied to the signal electronics
by the power section, whereas the mechanical quantity actual valuessuch as rotary speed and position are supplied by the motor encoder.The setpoint values are provided to the signal electronics by a high-er-level controller, to which the actual values are also communicated
In addition to the necessary control functions, the signal electronicsalso takes care of protection functions and prevents impermissibleoverloading of both the power section and the motor
1.3 Classification of electrical drives
Electrical drives are very diverse and are available in many different signs It is therefore relatively difficult to classify them and can only bedone so by selecting certain criteria, i.e from a particular perspective.The combination and exact selection of these criteria then give a wide-range of possible drive solutions
de-In the following the electrical drives are classified based on the ing criteria:
follow-• adjustability of the speed
• motor type and drive controller
• technical data
1.3.1 Speed variability
The requirements of an application on speed variability are often sive for the selection of the drive solution Depending on their speedvariability, drives can be roughly divided into three categories:
Closed-loop variable-speed Electrical drives
Open-loop variable-speed
Trang 20Fixed-speed drives
Fixed-speed drives are operated at a single, constant speed They
pos-sess only the equipment necessary for switching on and off, as well as
for protecting against overload It is not possible to vary the speed of
the drive, which means that depending on the load the speed may
fluc-tuate Typical applications for fixed-speed drives are fans and pumps
which are operated with an asynchronous motor direct-on-line
Variable-speed drives
The speed of variable-speed drives is adjustable and the drives can be
operated at at least two different speeds In addition to an electric
mo-tor, these drives have a controller which is responsible for adjusting the
speed Depending on the application, the controller is accordingly
com-plex and allows for different speed-ranges and accuracy
• Switchable-speed drives allow operation at at least two different
speeds Example applications are switchable-speed fans and pumps
or traversing drives with forward and reverse operation
Asynchro-nous motors together with the necessary contactor controller are
typically used
• Open-loop variable-speed drives have a continuously variable speed.
However, there is no feedback of the actual speed, meaning that,
de-pending on the drive type, there may load dependent deviations
from the speed setpoint A controller with an electronic power
sec-tion is necessary for the speed control Examples of this type of drive
are asynchronous motors with frequency controllers and V/f control
• Closed-loop variable-speed drives also have a continuously variable
speed but, in addition, measure the actual speed of the motor In this
way, deviations in the speed from the speed setpoint can be
rec-ognised and corrected To enable this, it is necessary to have a
con-troller with the appropriate control algorithms A very widespread
implementation of the closed-loop variable-speed drive is the
asyn-chronous motor with frequency controller and vector control
Figure 1.10 Frequency converters and asynchronous motors for
variable-speed drives
Trang 21Servo drives Servo drives are optimised to realise changes in speed very fast and
precise They are therefore well suited for complex motion tasks whichare characterised by continuously changing speeds Servo drives areused in all areas of machine building and are frequently realised usingsynchronous motor and servo controllers
Operating
quadrants
Closely related to the speed adjustability is the ability of a drive tochange its direction as well as to return energy to the supply system.These drive characteristics can be represented in a speed-torque dia-gram Depending on the sign (plus or minus) of the speed and thetorque, four quadrants can be defined (see Figure 1.12) In the two mo-toring (driving) quadrants both speed and torque have the same sign
In the generating (braking) quadrants the signs of the speed andtorque are opposite
Figure 1.11 Controllers and motors for servo drives
Figure 1.12 Classification of electrical drives by their operating quadrants
generating
Quadrant 4 generating Quadrant 3
motoring
Torque M
M
M M
M
Trang 22Depending on the design of the controller, the electrical drive operates
in the first quadrant only, e.g a pump, or in all four quadrants, e.g a
hoist
1.3.2 Motor and controller types
Over the course of time, different types of motor have established
themselves, each type with strengths and weaknesses, as well as a
pref-erential power range For this reason, and coupled together with the
very long life of the motors themselves, almost all motor types can still
be found in use today Taking the variety of controllers available
addi-tionally into account, results in a wide spectrum of drives Figure 1.13
shows a classification of the basic motor types together with their
Contactor control
Squirrel-cage rotor Permanently
excited Reluctance
line operation
Direct-on-Soft starter
Slip-ring rotor Separately
Trang 23According to the motor current, drives are divided into DC drives and
AC drives (single-phase and three-phase)
• DC drives use a DC motor In the lower power range the magnetic
field is produced by permanent magnets, in the higher power rangewith the help of a separate excitation winding For servo applicationshighly dynamic pulse-controllers are used, whereas for variable-speed drives converters are used as the controller
• AC drives use motors which are operated from a single-phase or
poly-phase AC current The frequency of the motor current has a cant influence on the motor speed Synchronous motors follow thefrequency of the supply current exactly, whereas in the case of asyn-chronous motors there is a difference between the frequency of themotor current and the rotational frequency
signifi-Drives with synchronous motors generally have a controller nous motors can be operated direct-on-line as well as together with acontroller The choice of the controller depends on the required speedrange as well as the required accuracy
Asynchro-1.3.3 Technical data
drives Of central importance are the mechanical and electrical teristics of the motor The most important technical data are recorded
charac-on the rating plate (see Figure 1.14)
Rated data,
motor
Of particular significance are the rated data They specify the motor atits rated operating point; they can therefore be used to compare differ-ent motors with each other Rated data are also known as nominal data
• Motor type: declares whether the motor is a DC, single-phase AC or
three-phase AC motor
Figure 1.14 Example of a rating plate of an asynchronous motor
3~Mot 1LA7166-2AA60 E0107/471101 01 001 IEC/EN 60034
93 kg IM B3 160L IP55 Th.Cl F D-91056 Erlangen
50 Hz 400/690 V /Y 18,5 kW 32,5/18,8 A cosϕ 0,91 2940 /min
60 Hz 460 V 21,3 kW 32,0 A cosϕ 0,92 3540 /min 380-420/660-725 V /Y
34,0-32,0/19,6-18,5 A
440-480 V 33,5-31,0 A
Thermal class Order number
Serial number Weight Manufacturer
Rated voltage Rated frequency
Rated power
Rated current Power factor
Rated speed
Degree
of protection
Frame size Type of construction
60 Hz data
50 Hz data
Trang 24• Rated voltage: voltage at, or voltage range within which, the motor
can be operated continuously Overvoltages within a certain range
are permissible for a short period
• Rated current: current with which the motor can be operated
continu-ously without leading to thermal overloading Overcurrents within a
certain range are permissible for a short period
• Rated power: mechanical power which the motor delivers at its rated
operating point The electrical power consumed can be calculated
from the given electrical data If both the electrical and mechanical
data are known, then the efficiency of the motor can be calculated
• Power factor: the power factor enables the active power consumed at
the rated operating point for single-phase and three-phase AC
mo-tors to be calculated
• Rated frequency: frequency of the supply voltage for single-phase and
three-phase AC motors In the case of asynchronous motors, the
rat-ed frequency is usually the same as the line supply frequency, which
for industrial networks in Europe is 50 Hz
• Rated speed: speed of the motor at the rated operating point.
• Rated torque: torque which the motor delivers when operating with
the rated current This value is of particular importance when
select-ing a servo motor
Rated data, controller
Once a motor has been selected based on its rated data, a suitable
con-troller can be found The concon-troller is specified by its electrical data:
• rated voltage: voltage at, or voltage range within which, the
control-ler can be operated In addition to the voltage, the line supply
config-uration (single-phase, three-phase, earthing concept) is of
impor-tance when selecting the controller
• rated current: output current which the controller can deliver
contin-uously Many controllers allow overcurrents for a short period, e.g
for accelerating
• pulse frequency: frequency with which the frequency controller and
servo controller switches the motor voltage The higher the
frequen-cy, the more dynamic and quieter the drive is
Mechanical design motor data
In addition to the motor rated data, a range of constructive data is
re-quired They serve to match the motor to the driven machine and to its
environment
• Type of construction: describes the permissible direction of mounting
and mechanical installation of the motor The types of construction
are described in international standards and are classified as: IM yzz
(International Mounting) according to Table 1.1
• Frame size (shaft height): the distance in millimetres between the
centre of the motor shaft and the outer edge of the motor
Trang 25• Thermal class: defines the maximum permissible motor temperature.
Exceeding this temperature may lead to premature ageing of thewinding insulation and therefore to early failure The thermal classesare defined in international standards and are recorded using a sin-gle capital letter Example: Thermal class F denotes an average per-missible motor temperature of 140 °C
• Degree of protection: classifies the degree of protection of the motor
provided against the ingress of solid objects The degrees of tion are documented in international standards and are classified asfollows:
protec-IPxy (International Protection) with
In addition to the data named, there are numerous additional teristics used for specifying a motor These are described in detail inthe manufacturer’s catalogue
charac-Table 1.1 Examples of motor mechanical design classification
B: horizontal V: vertical
specified by either one or two digits
Table 1.2 Example of motor degree of protection classification
with body parts and ingress of solid eign objects
for-y: degree of protection against ingress of liquids
e.g
IP54
5: ingress of dust is not entirely prevented but
it must not enter in sufficient quantity to interfere with satisfactory operation, com- plete protection against contact with tools or similar objects
4: protection against water
splashing from any direction
Figure 1.15
Asynchronous motor with IM B3 type of construction and IP55 degree of protection
Trang 26System data
The system data describe the characteristics of open-loop and
closed-loop controlled drives comprising of motor, encoder, and controller
They are usually not published by the manufacturer and must be
re-quested
• Speed range: range, in relation to the rated speed, within which the
speed can be adjusted with a specified accuracy
• Speed and torque accuracy: deviation between the setpoint and actual
value in relation to the rated value
Servo drives have additional relevant system data which are described
in more detail in later chapters
Trang 27Electrical drives provide the machine to be driven with mechanical ergy To describe the flow of mechanical energy and the associatedmovement, the physical quantities and laws of translational and rota-tional motion are used They are summarised in the following table.
en-Table 2.1 Quantities and equations of translational motion
per unit time dt
dv per unit time dt
The instantaneous power P is the uct of the actual force F and the actual speed v.
Table 2.2 Quantities and equations of rotational motion
angle dφ per unit time dt.
angular
in angular speed dω per unit time dt
force which acts on a lever of length r.
Trang 28moment of inertia J kg m 2 The torque M necessary to accelerate is
the product of the moment of inertia J
and the angular acceleration dω/dt
The instantaneous power P is the uct of the actual torque M and the actual
prod-angular speed ω
efficiency η The efficiency η is the ratio of the power output to the power input.
frequency f Hz (Hertz) The frequency f describes the number of oscillations per unit time.
frequency f
speed n n = f · 60 (in Hz) 1/min The speed n corresponds to the fre- quency f when expressed in 1/min
transmission ratio,
Table 2.2 Quantities and equations of rotational motion (cont.)
Trang 293.1 Fields in electrical engineering
Electrical drives utilise the effects of fields A field defines a space inwhich forces act upon objects or particles A field pattern is used to vi-sually represent the action of the force The action of the force is tan-gential to the field lines The closer the field lines are together, thegreater the action of the force
In electrical engineering, electric fields and magnetic fields are of nificance (other fields that exist are for example gravity fields andsound fields) Both fields are utilised in electrical drives
electrical particles (see Figure 3.1) The forces are exerted by thecharged particles themselves Charged particles can either be positively
or negatively charged The following applies:
• similarly charged particles repel each other
• oppositely charged particles attract each other
If charged particles are introduced into an electric field, they begin to
move, resulting in an electric current The electric current describes the
number of charged particles which move from point a to point b in adefined time Depending on the direction of movement of the chargedparticles, energy is either set free or absorbed
The electric voltage describes the electric field in total, and can be
inter-preted as a measure of the difference in energy of a charged particle atdifferent points in the electric field in relation to its charge
Figure 3.1 An electric field
The force exerted on a positively charged particle
is tangential to the field line
a
b
Vab
Positive charge
Negative charge Field lines
Trang 30Magnetic field
A magnetic field describes a space in which forces act upon magnetic
bodies (see Figure 3.2) This results in, for example, a magnetic needle
aligning itself in a magnetic field
A magnetic field can be produced in two different ways:
• in the case of natural magnetism the magnetic field is a property of
the material Certain materials, e.g “hard” magnetic iron, are
sur-rounded by a magnetic field
• in the case of an artificial magnetic field the magnetic field is created
by the movement of electric charge carriers (current flow), e.g in an
electrical conductor All current carrying conductors are surrounded
by such a magnetic field
Both effects for creating a magnetic field are used in electric motors
The magnetic fields in motors are channelled in magnetic circuits made
from iron Air clearances and gaps are kept as small as possible as they
weaken the magnetic field Iron amplifies the magnetic field
Magneti-cally, iron can be classified as being magnetically “soft” or “hard” (see
Figure 3.3):
• “soft” magnetic iron is only itself magnetic when it is within an
exter-nal magnetic field If the magnetic field is removed, e.g by switching
off the magnetic-field producing current, then the iron is also no
longer magnetic “Soft” magnetic iron has a very small hysteresis
loop area and therefore low magnetizing and demagnetizing losses
For this reason, motor components subject to changing magnetic
fields must be constructed from “soft” magnetic iron
• “hard” magnetic iron is characterised by a remanent (retentive)
mag-netic field It is suitable for use in permanent magnets However
“hard” magnetic iron is seldom used for the permanent magnets in
motors as other, magnetically stronger materials such as
samarium-cobalt (SmCo) or neodymium-iron-boron (NdFeB), are available
Figure 3.2 A magnetic field
Magnetic needle
Earth's magnetic field current carrying conductorMagnetic field of a
i
Field lines run from the geographic south pole to the geographic north pole
Trang 31The magnetisation characteristic of iron, which describes the magnetic
flux density as a function of the field strength H, is not linear For the
purpose of simplification, two areas can be defined:
In the “linear” range the flux density B is proportional to the field strength H, i.e the current in the windings, which produce the magnet-
ic field
Once in the saturation range, further increasing the current leads only
to a small increase in the flux density B The operating point in motors
with regard to their magnetisation is therefore chosen to be at the end
of the linear range
3.2 Developing torque3.2.1 Lorentz force
Force on a
charged particle
Of central importance for the function of an electric motor is the cal effect that when an electrical charge is moved in a magnetic fieldthen it experiences a force This force is known as the Lorentz force.The Lorentz force does not act upon static charges
the electrical charge, the direction of the magnetic field and the ing force All three components are mutually perpendicular As a visualmnemonic, the individual directions can be determined using threefingers of the right hand (not the left) as shown in Figure 3.4
result-Force on a current
carrying conductor
In electric motors the charge carriers move in electrical conductors If acurrent-carrying conductor is placed in a magnetic field, then thecharge carriers experience the Lorentz force The charged carrierstransfer this force effect to the conductor, from which they cannot es-cape As a result, the whole Lorentz force acts upon the current-carry-
Figure 3.3 Magnetisation characteristic of iron
"Soft" magnetic iron
Magnetisation characteristic
"Hard" magnetic iron
Saturation range
Area of the hysteresis loop is a measure
of the magnetisation/
demagnetisation losses
Remanence flux density
"linear" range
Trang 32ing conductor If the conductor is not mechanically fixed, then it will
move according to the acting force This effect is put to use to develop
torque in electric motors
Strength of the Lorenz force
The strength of the Lorentz force is proportional to
• the strength of the magnetic field, as well as
• the speed and number of charged particles moved and therefore
the strength of the electric current
This completes the overview of the most important factors responsible
for developing a large torque in an electric motor
By using strong magnetic fields and large currents, large torques and
therefore a large force effect can be achieved
Note: With the exception of reluctance motors, all electric motors use
the effect of the Lorentz force In the case of reluctance motors, the
torque is developed by the attraction force between electromagnets
and iron
3.2.2 Current carrying loop in a magnetic field
Force on a current carrying loop
To convert the Lorentz force of the current-carrying conductor into
torque the conductor is made into a loop The loop consists of a long
forward conductor and a long return conductor as well as the
connect-ing conductors between the forward and return conductors The loop
can turn about an axis and is in a magnetic field
If a voltage is applied to the loop, a current will flow in the loop (see
Figure 3.5) The direction of current flow in the forward and return
conductors in relation to the magnetic field is different As a result, the
forward and return conductors of the loop are subjected to two
oppos-ing components of the Lorentz force These two components actoppos-ing
up-on the lever arm of the loop result in a torque being developed As the
loop is pivoted, it is accelerated and makes a rotational movement
Figure 3.4 The right-hand rule
Thumb: Direction of movement
of positively charged particles (technical direction of flow of current) Index finger:
direction of the
magnetic field
Middle finger:
direction of the force
F B
I
Trang 33Upon reaching the horizontal position, the rotational movement of theloop would come to an end This very simple design is therefore notsuitable for use as an electric motor A technically usable motor re-quires
• many loops, with each loop arranged offset to its neighbour
• the loops to be stacked in many layers and further developed into real motor windings, and
• the direction of current flow, or the direction of the magnetic field,
to be changed over time
The change in current or magnetic field over time is taken care of either
by the motor itself (as in a DC motor) or by applying a time varyingvoltage to the motor (AC motor)
3.2.3 Induced voltage
Creation of the
motor emf
Consider a rotatable loop in a magnetic field Depending on the angle
of rotation, the number of magnetic field lines passing through theloop is either larger or smaller
Loop
F1
F2 B
Loop
F1
F2 B
i
S
Trang 34During one complete revolution the magnetic field passing through
the loop changes continuously This change over time results in an
elec-tric voltage being induced in the loop (see Figure 3.6) This voltage can
be measured across the ends of the loop It is called the electromotive
force (emf)
The emf is larger if
• the loop consists of many windings and
• the loop rotates faster in the magnetic field
Advantages and disadvantages of the emf
In generators the emf is utilised to generate voltage In motors,
howev-er, the emf is a speed dependent disturbance which must be
compen-sated for by the motor terminal voltage Only when the motor terminal
voltage exceeds the emf does current flow and a motoring torque is
de-veloped The motor emf increases with increasing speed This results in
a continually higher motor terminal voltage being required to maintain
a motoring current in the motor windings
3.2.4 Quantities and equations of electrical engineering
Kirchhoff’s circuit laws
For calculating electrical networks Kirchhoff’s circuit laws may be used:
voltage law: the sum of all voltages in a loop is zero
current law: the sum of the currents flowing into and out of a node
is zero
Table 3.1 Quantities and equations of electrical engineering
symbol
electric charge Q Q = n·e (Coulomb)C The electric charge is a multiple of the ele-mentary charge e.
electric field
A test charge with charge Q in an electric field of strength E exerts a force F
The integral of the electric field E along an
arbitrary path between two points defines
the electric potential V between the points.
electrical
F (Farad)
The capacitance is a measure of the ability to store charge.
The electric current intensity I defines the charge quantity Q which flows through a sur- face in time T.
electrical
Ω (Ohm)
The resistance characterises the ability to oppose the flow of current.
magnetic
T (Tesla)
In a homogeneous magnetic field the netic flux density is the quotient of the mag- netic flux Φ and its cross-sectional area A.
Trang 353.2.5 Components of electrical engineering
Equivalent circuit diagrams are used to describe the electrical
process-es in drivprocess-es Thprocess-ese circuits contain lumped circuit components whichdescribe the electrical processes based on the relationship betweencurrent and voltage
magnetic flux Φ (Weber)Wb The integral of the magnetic flux density B over an area A gives the magnetic flux which
flows through the area A.
magnetic
flux linkage ψ ψ = w·Φ (Weber)Wb The product of the number of windings w and the magnetic flux Φ is known as the
magnetic flux linkage ψ.
inductance L (Henry)H The inductance is a measure of the magnetic linkage created by a defined flow of current.
The induced voltage is proportional to the rate of change of the magnetic flux linkage ψ.
The instantaneous power P is the product of the instantaneous voltage v and the instanta- neous current i.
Table 3.1 Quantities and equations of electrical engineering (cont.)
inductance, coil,
H (Henry)
capacitance,
F (Farad)
motor
in general a network comprising resistance, inductance and a voltage source (emf)
v i
M
Trang 36Linear components
In linear components, the relationship between the current and voltage
can be described using a linear equation or linear differential equation
Non-linear components
In non-linear components, the relationship between the current and
voltage can, in its simplest form, be represented by a characteristic
curve
In electrical drives non-linear components are mostly used to describe
the power semiconductors in the controllers As the power
semiconduc-tors in electrical drives are usually used as switches to switch the
cur-rent on and off, the characteristic curves of these components can be
very much simplified
Table 3.3 Non-linear components in drives
Reverse direction Forward direction
v i
Reverse direction Blocked
Triggered
v i
Reverse direction Blocked Conducting
Trang 37drives with DC motors
in the motor has a certain ripple
DC drives can still be found widespread in industrial applications, though AC drives are increasingly displacing them
al-In the lower power range (< 500 W) they profit from the general ability of a DC 24 V power supply in almost all machines and industrialequipment Using permanently excited motors and very simple control-lers, very cost-effective small drives can be realised
avail-In the higher power range (> 100 kW) controllable DC drives are stillworth considering when comparing them with the cost and size of ACdrive controllers DC drives are today therefore still used for rollingmills, cranes, and elevators These drives have a high standard of con-
Figure 4.1 Functional blocks of a DC drive
Converter Starting
for starter control
and monitoring
Higher-level controller Higher-level controller
Current actual value
Actuator Actuator
DC drive
DC low-power drive
Speed actual value
Motor temperature
Switchgear and protection equipment
Trang 38trol and monitoring functions In the higher power range separately
ex-cited DC motors are used
Lastly, but still of significance, DC drives are still in use in many older
machines and industrial plant As these machines and industrial plant
must be serviced and maintained, it is still necessary to have a good
un-derstanding of DC drives in an industrial environment
In general, DC drives profit from good and easy-to-understand
control-lability For this reason, they are an ideal introduction to the world of
controlled electrical drives
4.2 The DC motor
4.2.1 Operating principle
Current-carrying loop
The operating principle of the DC motor can be best explained using
the current-carrying loop introduced in Chapter 3
A rotatable loop is exposed to a magnetic field If a DC voltage is applied
to the ends of the loop, a current will flow in the loop The direction of
current flow in both long sides of the loop is in opposite directions (see
Figure 4.3) As a result, the Lorentz force components acting upon the
two long sides of the loop are also opposite These two components
re-sult in a rotational movement of the loop
Once the loop reaches a horizontal position, the two Lorentz force
com-ponents cancel each other out If the loop moves past the horizontal
po-sition, then the components of the Lorentz force act to prevent any
fur-ther movement The loop is braked and subsequently pulled back into
the horizontal position, in which it remains
Commutator
If the rotational movement of the loop is not to end in the horizontal
position, then shortly just after passing this position the direction of
current flow must be reversed This function is carried out using a
com-mutator
Figure 4.2 DC motor
Trang 39In Figure 4.4 the commutator is shown as a disc with two isolated halves Each half is connected to one end of the conductingloop The electrical connection to the DC supply is made through fixedbrushes which slide over the surface of the commutator The brushesare arranged so that when the loop reaches the horizontal position theyconnect to the other half of the commutator In this way, the polarity ofthe electrical supply is reversed, and so too the direction of currentflow The Lorentz forces now act in a way to continue the rotational mo-tion of the loop.
electrically-Disadvantages
of the loop
If a DC motor were to be constructed from just a single conducting loop
in a magnetic field, then it would have significant disadvantages:
1 In order to develop very large Lorentz forces, i.e torques, a verylarge current would have to flow in the conducting loop The cross-sectional area of the conductor of the conducting loop would have to
be sized accordingly
2 If the current were to be switched on when the loop is exactly in thehorizontal position, the Lorentz forces would compensate them-selves and there would be no rotational movement The loop wouldremain stationary
Figure 4.3 Loop with commutator in a magnetic field
Figure 4.4 Function of a commutator
N
Axis of rotation
Conductor loop
Commutator
DC voltage source
Brushes
i
S
B i
Trang 403 The Lorentz force always acts in the same direction This results in
the turning force exerted on the loop being dependent on the
posi-tion of the loop itself In the vertical posiposi-tion the force is at its
maxi-mum, and in the horizontal position there is no force at all This
means that the torque acting on the loop (in the radial direction) is
not constant but a sinusoidal function varying between zero and a
maximum value
From loop to armature winding
To eliminate these disadvantages, practical DC motors are constructed
differently
The conducting loop is replaced by a multiple-layered armature
wind-ing made from insulated copper wires (see Figure 4.5) When an
elec-tric current flows in the winding, it cuts the magnetic field as often as
the number of turns of the winding This results in multiplication of
the Lorentz force
To achieve a more constant torque, instead of using a single winding,
many part-windings are used Each of these part-windings is arranged
offset to its neighbour and connected in series The ends of the
wind-ings are terminated at the laminations of the commutator Depending
on the position of the commutator, a part-winding is short circuited
and two parallel paths consisting of several part-windings are formed
Figure 4.5 shows an arrangement consisting of four part-windings The
active winding parts are going into the diagram, and therefore only the
cross-sections of these part-windings can be seen The winding heads
are not shown The ends of the windings are connected to the four
com-mutator laminations The in-series connected part-windings 1-2-3-4-1
can be clearly seen
Figure 4.5 Current flow in the armature windings of a DC motor
-Winding 1: current carrying
Winding 2: short circuited
Winding 3: current carrying
Winding 4: short circuited
Winding 1 in shunt to Winding 3
Winding 1: current carrying Winding 2: current carrying Winding 3: current carrying Winding 4: current carrying Winding 1 in series to Winding 4 Winding 2 in series to Winding 3 Winding 1-4 in shunt to Winding 2-3
2
4
4 3
3