Sparks Electrical News August 2017

MOTOR CONTROL CENTRES AND MOTOR PROTECTION

16

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. 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. from the 13 th undertone, which produces a speed of 7.7% of rated rpm. In the reverse direction, creep backward is based on the 11 th undertone a 9.1% of rated rpm, while jog backward and fast jog backward are based on the 5 th (20%) and 3 rd (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.

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 3 rd undertone or 33% of rated rpm; a jog forward at the 7 th undertone or 14.3% of rated rpm; and a creep forward generated

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.

Enquiries: www.abb.co.za

POWER DISTRIBUTION IN CONFINED SPACES

S tandardisation 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/www.rittal.co.za

SPARKS ELECTRICAL NEWS

AUGUST 2017