We've gone way beyond "on" and "off." Yes, power supplies always had to convert and deliver appropriate volts, watts, amps and other power levels, and meet quality measures to run their machines and applications. But once configuration was done and harmonics were tested, most power supplies operated continuously—at least until an interruption or outage happened.
Well, those set-it-and-forget-it days are long gone. Digital monitoring devices enabled by microprocessors and software are pulling power supplies up to the same awareness level as so many other process control components.
For instance, Boliden recently spent $790 million to renovate its Aitik open-pit copper mine in Gällivare, Sweden, and it used ABB's control systems and power equipment to increase Aitik's efficiency and double capacity to 36 million tons of ore per year, even though its initial ore is only 0.25% copper (Figure 1). The mine installed 650 motors ranging from 4 kilowatts (kW) to 5 megawatts (MW); 230 drives and variable-speed drives; and two 22.5-MW gearless mill drives (GMDs). These are powered by ABB's 23 distribution transformers and gas-insulated switchgear and controlled by its System 800xA DCS.
Of course, extracting metal from the 106,000 tons of ore that's crushed and chemically concentrated to 25% copper at Aitik each day requires lots of stable, high-quality power for its 7 km of conveyors, the GMDs and other equipment, which must often run 24/7/365 in very dusty conditions that can get down to -45 °C in winter. So, ABB implemented a 179-kV substation with its gas-insulated UniGear switchgear that's protected by its Relion relay protection equipment, and distributes 24-kV power throughout the mine's operations. Also, a harmonic filter and power-factor correction system help Boliden prevent damage to its own equipment and avoid disturbing the local power grid.
In addition, Aitik uses the IEC 61850 standard that defines communications within and between electrical components, which enables 800xA to provide one environment for supervising and controlling process automation equipment, power automation devices, switchgear, and transmission and distribution equipment. Boliden reports that integrating Aitik's electrical controls with its process controls increases productivity and reduces stoppages.
While most process applications aren't as big as the Aitik mine, many similar methods of monitoring and proactively maintaining electricity are being adopted by smaller power supplies in diverse applications.
"Power supplies have always been a bit of a stepchild compared to other process control devices, but users in applications from power generation to food and beverage are recognizing that power is the most critical element in their applications," says Roolf Wessels, business unit manager for monitoring and protection at Pepperl+Fuchs. "You can lose a few I/O points and networking nodes and still run an application, but losing power means losing your whole application, so it's worthwhile investing in high-reliability, high-efficiency power. As a result, users want more diagnostics in their power supplies. They already have diagnostics for predictive maintenance and asset management in their controllers and field devices, and now they want it in their power supplies, too."
As a result, Pepperl+Fuchs redesigned its PS 3500 power supply in 2009, and is scheduled to introduce its PS 3500-DM diagnostic module in January 2013. "It plugs into the power supply's backplane and monitors incoming current quality and generated dc outputs, checks for brownouts and spikes, time-stamps any events, correlates them with data from other sources, and provides alerts and alarms," says Wessels. "We even added a display on the DM module itself, so users see all their parameters locally too."