Sparks Electrical News August 2017

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SPARKS
ELECTRICAL NEWS AUGUST 2017
16 MOTOR CONTROL CENTRES AND MOTOR PROTECTION
Slow speed Jog – BRIDGING THE GAP BETWEEN SOFTSTARTERS AND DRIVES
ABB has been part of the development of electric motors for more
than 100 years. With the introduction of variable speed drives (VSDs) it
became possible to control the speed of the motor, while in the 1980s
the softstarter was introduced to reduce start-up torque by temporarily
reducing the voltage and/or current when the motor first starts.
ABB’s PSTX now takes soft starting to the next level by bridging the
gap between softstarters and drives.
ABB has included a host of new features for full speed applications
that were previously only available with drives/VSDs, while still keeping
softstarter core values of compact size, lower heat generation and lower
cost. The PSTX starter offers over- and under-voltage protection, limp
mode, motor brake and motor heating, but the feature that draws most
attention is the slow speed jog, a function that allows the motor to be run
at reduced speed.
The PSTX flagship softstarter for motors driving control products
makes speed regulation possible without the need for using a VSD. The
slow speed jog function enables the motor to be run at three different
reduced speeds in the forward and reverse directions. This is achieved by
reducing the output frequency from the softstarter, which proportionally
reduces the speed. The result is a compact and cost-effective starter that
also offers temporary speed control of a motor.
In contrast to a drive, the PSTX generates undertones (or sub-har-
monics) of the fundamental frequency, typically 50 Hz or 60 Hz grid fre-
quency. These are used to trigger the thyristors in a specific sequence to
generate a new output frequency to drive the motor.
The PSTX can run the motor in three different forward speeds: a fast
jog forward at the 3rd undertone or 33% of rated rpm; a jog forward at
the 7th undertone or 14.3% of rated rpm; and a creep forward generated
from the 13th undertone, which produces a speed of 7.7% of rated rpm.
In the reverse direction, creep backward is based on the 11th undertone
a 9.1% of rated rpm, while jog backward and fast jog backward are based
on the 5th (20%) and 3rd (33%) undertones respectively.
The benefits? Combining the backward jog with the kick-start func-
tion offers a solution for pump cleaning, for example. The jog can also
be applied in many other situations; e.g. positioning of conveyor belts, to
simplify maintenance inspections of machinery and to ensure full func-
tionality of an application during commissioning.
To ensure the function is easily operated, the jog can be controlled in
several different ways: with the detachable keypad, with push buttons or
via fieldbus communication.
Enquiries:
Standardisation of control gear and
switchgear is one of the most effective
ways to reduce engineering and
configuration costs. This is true for products
both large and small – as Rittal demonstrates
with its new RiLine Compact busbar system.
The busbars do not require holders, and
have end-to-end contact hazard protection.
Switching and protective devices can be
connected quickly and easily – saving time
and effort during engineering and downstream
installation. These save time and materials, and
improve operator safety.
The new Rittal RiLine Compact, designed for
control units that require a maximum current
of 125 A, addresses this need. Despite its size,
the busbar system distributes power effectively
and reliably, in compliance with all applicable
standards. The innovative technology is ideal for
small switchgear and controllers, and for direct
integration into plant and equipment.
RiLine Compact marks Rittal’s entry into a
new market segment for low-current power
distribution. It comprises a board with busbars
entirely enclosed in covers that safeguard
against unintentional contact. A connection can
easily be established anywhere along the length
of a busbar via a series of access apertures
(called the pitch pattern) in the board.
Switchgear and control units can be ‘plugged
in’ simply using a variety of adaptors. In addition,
an adapter for connection to round conductors is
available, as well as a variety of functional modules
for motor and power control.
One of RiLine Compact’s primary strengths is
that it can be rapidly configured, assembled and
installed. The main board and diverse compo-
nents can be securely mounted without the need
for tools. Because the entire system is shielded
by covers, users are protected against live parts.
This enhances safety for operators and for the
system as a whole. Furthermore, it saves time
and cuts costs.
Enquiries: +27 (0)11 609 8294
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