Power Factor Correction Yields Healthy Savings for Pharmaceutical Distribution Center

By Consulting Specifying Engineer Staff August 15, 2006

Poor power factor, or inefficient use of supplied power, can often be overlooked because it has few outward signs. There are no blown fuses, tripped circuit breakers or failed electrical apparatus to alert plant personnel to the problem.

In fact, the most visible symptom, increased utility costs, is difficult to determine based on the utility rate structure—whether it is per kVA, per KW or some other billing method. While loss of some electrical efficiencies are typically inherent in the power system, the scope of the problem determines the extent of savings that are possible. Induction loads, especially where motors and transformers are found, fluorescent lights and variable frequency drives can use supplied power inefficiently.

At one particular pharmaceutical distribution center, the many small rated horse-power motors used to power the multitude of conveyors moving product around the 165,000-sq.-ft. facility were particularly susceptible to poor power factor.

The challenge was to determine the extent of the inefficiency, and then scrutinize utility invoices to determine whether the savings would offset the cost of equipment required. It’s a straight financial calculation, as is the ROI/payback period.

A power quality survey (sometimes called an audit or study) was commissioned. PowerEdge Technologies installed metering analyzers within the plant, which were left in place to collect data for one week. The data collected was used to build a “load profile,” which allowed the equipment vendor’s engineers to determine the extent of the power-usage inefficiencies and whether harmonics or other power anomalies were present.All of this information was then factored into the proper location-specific solution.

The distribution center had a power factor of 0.72 to 0.78, compared to the target of 0.95, so there was definitely room for improvement. While no harmonics were identified, a previously unknown phase imbalance was uncovered. Since the solution essentially involved installing capacitor banks on each phase, the phase imbalance had to be corrected (otherwise the power factor correction would actually compound the problem).

A 200-kVAR automatically switched capacitor bank was installed on the main 480-volt utility service. This solution was more economical and practical, while providing for simpler installation with maximum control for the facility engineer. Automatic switching allows the system to dynamically provide the necessary reactive compensation based on the load and demand at any given time. A 400-amp circuit breaker was also integrated as part of the power factor correction system, so that power can be disconnected for maintenance of the apparatus.

Total costs for the energy initiative amounted to $100,000. Installation, which occurred in August 2005, was a bit trickier than normal because the plant had to schedule a time to transfer over to the emergency power generator while the power factor correction equipment was being installed. The facility operates 24/7 and is fully climate controlled for product storage requirements. Annual savings (based on their actual usage and per kVA rates) were estimated to be $40,000, or 18%, for a 30-month payback. Approaching the two-year mark after installation, the overall package is said to be exceeding the savings estimates and performing as expected.

For more about power factor correction from Staco Energy Products, click here .