S&C PureWave Dynamic Voltage Restorer (DVR) Eliminates Voltage Sag Problems for Semiconductor Manufacturer

Case Study highlights how S&C Electric Company's Power Quality Products Division provides power quality solutions for the continuous process industry. Incorporating S&C's PureWave DVRs into the semiconductor manufacturer's power quality control system eliminated voltage sag problems, maintained production, and provided significant cost savings to the facility.

Manufacturing semiconductors is extremely sensitive to electricity supply variation. One brief voltage sag can cost millions of dollars in damaged or scrapped product, lost production and restarting expenses.

This problem was faced by a major, Arizona-based semiconductor manufacturer which produces microprocessors for personal computers. The production equipment includes highly sensitive loads that cannot tolerate such power quality problems such as very short duration voltage sags and swells. Yet during one twelve-month period in the late 1990s, the facility experienced 13 such sags from the serving electric system, resulting in economic losses in the millions of dollars.

Consider the semiconductor chip production process. During certain stages, light is applied to photosensitive layers to create the circuit paths. A microprocessor is made up of hundreds of such layers. If a significant voltage sag occurs during the typically seven-to-fifteen day production cycle, the entire work-in-process could be scrapped. In this instance, costs for one incident could total $200,000 to $2,000,000.

The problem was solved by installing two S&C PureWave DVRs in 1997. The solution proved so effective that another two PureWave DVRs were installed at another new fab, at that same site in 2001.

The Solution: S&C PureWave DVR Dynamic Voltage Restorer.

The original decision to install the PureWave DVRs was made in consultation with and cooperation with Salt River Project (SRP), the serving electric utility. Although the manufacturer had optimized its supply with the utility, normal system operations, weather events and other factors -- can cause fluctuations in the supply of electricity. A number of solutions were considered to prevent voltage sags from impacting the manufacturers production process. The PureWave DVR was chosen for two major reasons:

Most of the power quality events were voltage sags of very short duration, but not outages. PureWave DVRs are particularly effective at compensating for voltage sags.

Extremely large load sizes. The connected loads at either of the plants can exceed 40 MVA; other solutions were considered impractical and prohibitively expensive.

Technical Considerations:

PureWave DVRs are solid-state electronic power conditioners that provide dynamic sub-cycle protection from power-supply problems. They accomplish this by restoring the quality of electrical energy delivered to the end users sensitive loads when the source voltage is out of specification.

Unlike UPS systems, DVRs protect sensitive loads from voltage sags and swells by supplementing, rather than replacing, power from the providing utility. During sags and swells, DVRs maintain the voltage applied to their associated loads within acceptable tolerances by injecting a compensating voltage of proper magnitude and phase angle into the line. Each PureWave DVR can inject from 20 to 50% of line-to-ground voltage independently on each of the three phases of the feeder, for up to 30 cycles. They can therefore correct for the vast majority of sags and swells originating on the transmission or distribution system.

For the initial installation, two 6-MVA S&C PureWave DVRs were procured. Each system was installed in series with one of the two 12.47-kV feeds serving the facility. For the first two systems, the site work was done in cooperation with SRP. For the second two systems, the solution was provided as a complete, turn-key installation.

Results: Sags Corrected, Revenue Retained and Investment Quickly Recouped.

The results of incorporating the PureWave DVRs into the manufacturers power quality control are impressive. Due in part, to a long stormy season during the first year of operation, the end user recouped the investment in less than one year. The PureWave DVRs corrected for all sags within their system rating, and the numbers of voltage problems were reduced to the point where there were none at all in 2001. The reliability and cost effectiveness of the units were such that an additional two 5-MVA PureWave DVRs were installed on another new fab on the same site. The four systems are sized for expansion to protect the load growth up to 100 MVA.

PureWave DVRs are manufactured by S&C Electric Company, global specialists in electric power switching and protection products. S&C provides the most complete line of power protection products and services available from a single company. The Chicago-based firm specializes in customized turn-key power quality solutions for utilities, industrial, commercial, institutional, data, telemetry, medical and other energy-sensitive and power-critical applications worldwide. Information about S&C is available at www.sandc.com/PQ/PR.