Ensuring a reliable power supply to a manufacturing facility—short of a full-scale power failure attributable to non-power-quality circumstances—is possible with voltage regulators. Two common types of active power-boost functions are the dynamic voltage regulator (DVR) and the series voltage regulator (SVR).
“SVR is applied for single loads, a critical load within a facility, for example, an extrusion process or printing line. The DVR is the big brother and is done for a whole plant, where you may have semiconductor production or pharmaceuticals,” says Tony Seibert, systems and senior engineer with ABB Power Electronics, New Berlin, Wis.
These plant-wide units have the ability to return their investment within a couple of outages, he says, something that is important because of the costs incurred. “For some of our clients, downtime could cost hundreds of thousands of dollars to millions of dollars per occurrence. Sometimes it may take them a few minutes or hours to recover power.”
A DVR generally will be a lower-cost solution than an uninterruptible power supply, or UPS, says Ken Mattern, manager of S&C Electric Co.’s Orlando, Fla., power-quality operations. The cost of “these large DVRs run between $150 and $250 per kVA (kilovolt ampere) of load.”
His company’s PureWave technology protects the Caledonian Paper Mill in Irvine, Scotland. The mill, which is part of UPM-Kymmene Group, has a single eight-meter-wide (approximately 26 feet) paper machine with a design speed of 1,450 meters per minute (approximately 4,750 feet per minute). It produces approximately 240,000 metric tons annually of light-weight coated paper. The facility is designed to operate 24 hours per day. Electricity is supplied through Scottish Power’s 132-kilovolt transmission system.
Power dips were problematic, says David Stewart, an engineer with Caledonian Paper. A feasibility study showed “the minimum dip was 84 percent of retained voltage and the maximum was 50 percent, with an average of 70 percent.” When voltage trips, problems are “not just with paper breaks, but secondary damage to rolls, felts, wire and fabrics, as well as quality problems when trying to settle the machine back down again after an outage.”
The DVR technology—there are two 2-megavolt ampere (MVA) modular units designed to recover 95 percent of all dips—has had a dramatic, positive impact on operations, Stewart says. “Prior to the installation of the DVR, the paper machine could be offline for up to 48 hours, due to secondary damage. Since DVR installation, all dips up to 50 percent retained voltage and 300 milliseconds (ms) have been compensated. However, any dip longer than 300 ms still results in a machine shutdown, but without secondary damage to press-section equipment.”
See the story that goes with this sidebar: Manage power, shield processes, save money
