April 2021

Drives & Controls & BACK TO BASICS n SPONSORED BY Cabling best practice Part 3: Routing Have you ever experienced instruments giving readings from variable-speed drives that are clearly inaccurate or sporadic? The problem may lie, not with your drives, but with the way their cabling is installed, as ABB's Martin Richardson explains. B ecause of the way that variable-speed drives (VSDs) work and use power electronics, it is essential that the routing of their cables is considered carefully, otherwise other electronic equipment in their vicinity could suffer from interference. Firstly, ensure that the motor cable is separated adequately from the signal or control cables (by at least 500mm) and from other power cables (by at least 300mm). Secondly, ensure that all other cables are separated adequately from the signal or control cables by at least 200mm, to avoid interference. When control cables must cross power cables, make sure that the crossover angle is as near to 90 degrees as possible. To prevent cross-coupling, it is also important to avoid mixing pairs with different signal types – 110V AC, 230V AC, 24V DC, analogue or digital. For example, an unsuppressed relay coil switched at 110V can transmit a surprisingly large transient pulse into an adjacent 24V DC or analogue signal line. Cable trays should have good electrical bonding between each section and to the grounding electrodes. Stainless-steel or aluminium tray systems can be used to improve the local equalisation of potential and reduce the problem of corrosion. If you are using plastic trunking, secure it directly to the installation plates or framework. To avoid antenna affects, you should not run spans in mid-air. It is advisable to use twisted-pair wires with equalising conductors wherever possible to avoid differential mode disturbances, which can lead to spurious signals. In some installations, it may be beneficial to use ferrite rings to avoid common-mode disturbances. These disturbances do not distort the signal itself, but can disturb the receiving device. Installers should endeavour to keep wires twisted and as close to the terminal as possible. You should avoid unused wires in cables. They should be connected to ground or to another signal. There is no right or wrong way of doing things, but pump manufacturers, contractors or end- users should double- check any system they are proposing. With thousands of installations in the UK alone, it is fair to say that we have seen a lot of problematic applications and this has moulded our best engineering practice. n COMMENT n COVID AND ROBOTS: BAD NEWS AND GOOD One of the many casualties of the Covid-19 pandemic has been the industrial robots market. In fact, the sector was already starting to suffer in 2019 before the arrival of the virus. According to a new report from Interact Analysis (www.interactalysis.com ), the downturn in the global economy in 2019 led to a 5.4% fall in global robot shipments. Last year, sales fell by a further 5.9% and 80,000 fewer robots were sold than previously expected. This marked the first period of continuous negative growth ever experienced in the normally buoyant industrial robots market. But the pandemic is now proving a fillip for the sector. The need to ensure social distancing in factories and realisation is that vulnerable humans can be a weak link in production, is spurring renewed interest in what automation on general – and robots, in particular – can do to help manufacturers exit from the pandemic. New applications are emerging in sectors that have previously spurned the use of robots. Interact is now predicting that revenues in the industrial robot market will surge by 9.2% this year, with shipments rising by 9.6%. Some technologies will fare better than others. Collaborative robots (cobots) which experienced negative growth for the first time in their short history last year, are now expected to deliver 15-20% of year-on-year growth over the period to 2028. Scara and delta robots, which are finding new uses in pick-and-place and assembly applications, are also expected to bounce back quickly. But sales of articulated robots, whose fortunes are linked closely to those of the automotive sector, are not likely to recover before 2022. The market for industrial robots is dominated by four suppliers – Fanuc, Yaskawa, ABB and Kuka – which between them accounted for around 58% of the sector’s revenues in 2019. But their traditional strength in the market for articulated arms may prove a weakness going forward as new entrants emerge bringing with them“exciting new technologies”, Interact suggests. In recent months, there has been a flurry of announcements, many from start-up companies on California, of“breakthrough” technologies that are set to revolutionise the robotics market. And they are attracting substantial funding to put their ideas into practice. For example, one entrant, called Symbio Robotics, has raised $30m to help it modernise industrial manufacturing by using artificial intelligence to make robots faster, more capable and more flexible. Another, Fort Robotics, has attracted $13m to back its safety and security technologies for autonomous machines. Good news for potential purchasers is that these enhanced robotic technologies will not necessarily mean higher costs. Interact Analysis predicts that industrial robot prices will fall by 3–5% a year over the period 2019–2024. So, while Covid may initially have been bad news for the robotics industry, it may, in the longer run, drive significant growth in the sector. Tony Sacks, Editor