Softstarters - ABB PSR Manual

Softstarters

From the moment the first electrical motors was developed,
engineers have been searching for a way to avoid electrical
and mechanical problems that usually occur when starting
the motor. These problems include high inrush current and
current spikes as well as excessive mechanical wear. One
traditional way to avoid this is to use a star delta starter.
This starting method is in many applications insufficient,
as problems with current spikes and torque peaks will
remain. In addition, it does not provide any way to perform
a soft stop. A softstarter on the other hand will provide far
better performance during the start and also the possibility
to soft stop the motor.
ABB has been producing softstarters since the beginning of
the 1980's. The valuable experience gained since the early
80's has been incorporated into the design of today's product
ranges. Matching modern power electronics with smart circuitry
and software, the ABB softstarters offer superior control of the
current and voltage during motor start-up and stop, in addition
to several state of the art design features.
The solution to both mechanical and electrical problems
AC motors, "the workhorse of the industry", are used to drive
fans, crushers, agitators, pumps, conveyors, etc. Depending
on how it is installed, too often unnecessary and unwanted
torque and current peaks are an everyday reality in production
Motor voltage
V V
DOL Star/Delta
100 %
70 %
58 %
30 %
Graphs showing the basic differences between direct-on-line starting (DOL), star-delta starting and soft starting in terms of the motor voltage (V), motor current (I) and motor torque (T).
4 Softstarters | 1SFC132005C0201, rev.F
Motor current
I
Softstart
Adjustable
ramp slope
Time
plants all over the world, causing damage in several ways.
Among them are:
• Electrical problems due to voltage and current transients
arising from Direct-On-Line or Star-Delta starts. Such
transients may overload the local supply network and
cause unacceptable voltage variations that interfere with
other electrical equipment connected to the network.
• Mechanical problems that address the entire drive chain,
from motor to driven equipment, causing a big need for
service and repair as well as unwanted down time.
• Operational problems, such as damage to products on
conveyor belts.
• Water hammering and pressure surges in pipe systems
when starting and stopping pumps.
The financial consequences are considerable; every technical
problem and every breakdown costs money in terms of repairs
as well as lost production.
The easy solution to all of these problems is to install an
ABB Softstarter type PSR, PSS, PSE or PST(B). With ABB
Softstarters, it is possible to start and stop smoothly while
keeping mechanical and electrical stresses to a minimum.
Star/Delta
DOL
Softstart
Motor speed
Torque
T
DOL
Motor speed
Star/Delta
Softstart