The rapid adoption of automation techniques in industry has increased
the requirement for better process control. This has resulted in many new
applications for AC variable speed drives (VSDs) to control the speed and torque
of driven machinery. Variable speed drives (VSDs) are also used to meet
particular starting and stopping requirements.
The variable speed drives guide promotes a sound understanding of how
VSDs work and how to correctly select, install, commission and maintain
them. There is also detailed coverage of many typical applications in process
control and materials handling such as those for pumping, ventilation,
conveyers and hoists.
Our guide benefits anyone associated with the use of VSDs in the industrial
or automation environment. Our guide also helps those working in system
design as well as site commissioning, maintenance and troubleshooting.
Although a basic understanding of electrical/electronics engineering principles
is fundamental, even those with a superficial knowledge of VSDs will substantially
benefit from our guide.
In particular, if you work in any of the following areas, you’ll benefit
from our guide:
Consulting electrical engineers
Plant engineers and instrument technicians
Electrical maintenance technicians and supervisors
Instrumentation and control system engineers
Process control engineers
Goals of this guide -- learn the following:
The principles of AC variable speed drives for industrial speed control
The essentials of squirrel cage induction motors
The latest developments in power electronic converters used for VSDs
How to select the correct AC variable speed drive for industrial
How to identify faults on VSDs and how to rectify them
The key issues about flux vector control and how it can be used
in drive applications
The main concepts in interfacing the control circuits of VSDs with
PLCs/DCSs using serial data communications
Introduction. A review of the fundamentals in variable
speed drives including motion concepts, torque speed curves, types
of variable speed drives, mechanical variable speed drive methods and electrical
variable speed drive methods.
3-phase AC induction motors. These versatile and robust
devices are the prime movers for the vast majority of machines. This Section
covers the basic construction, electrical and mechanical performance,
motor acceleration, AC induction generator performance, efficiency of electric
motors, rating of AC induction motors, duty cycles, cooling and ventilation,
degree of protection of motor enclosures, methods of starting and motor
Power electronic converters. This section
deals with the active components (e.g. diodes, thyristors, transistors) and passive
components (e.g. resistors, chokes, capacitors) used in power electronic
circuits and converters.
compatibility (EMC). Interference in circuits
refers to the presence of unwanted voltages or currents in electrical
equipment, which can damage the equipment or degrade its performance.
The impact of variable speed drives can be severe and this Section examines what causes
interference and how to minimize its impact.
Protection of AC converters and motors. The protection of
AC variable speed drives includes the protection of the AC converter and the
electric motor. The main methods of protection are examined.
Control systems for AC variable speed drives. The overall
control system can be divided into four main areas of the inverter
control system, speed feedback and control system, current feedback and control
system and the external interface.
Selecting VSDs and AC motor converters. Although manufacturers' catalogs
try to make it as easy as possible, there are many variables associated
with the selection and rating of the optimum electric motor and AC
converter for a VSD application. This Section covers many of the
principles for the correct selection for AC variable speed drives,
which use pwm-type variable voltage variable frequency (VVVF) converters
to control the speed of standard AC squirrel cage induction motors.
VSD and Power Electronics Installation. The main issues here of
general installation and environmental requirements, power supply and earthing
requirements, start/stop of AC drives, installing AC converters into
metal enclosures, control wiring and commissioning variable
Special topics and new developments. Typical topics of soft-switching and the
matrix converter are examined here.