Control Engineering June 2014-CE : Page-76

ADVER TISEMENT Maximize Savings with the Right Variable Frequency Drive slashed the utility bill by enough to pay for the project in less than two years. Plus, they reduced utility demand charges by reducing inrush current at start-up.” Danfoss VLT ® Drives are soft-start devices that gradually ramp voltage up and down when starting and stopping, which eliminates sudden fluctuations in amperage that may result in demand charges. In operation, the drive can vary the current frequency from 0 to 32 kHz to deliver a variety of AC motor speeds. Motor speed can then be matched to the required fan RPM to maintain process quality and reduce electric consumption whenever full torque is not required. For its Ste. Genevieve cement manufacturing facil-ity, Holcim (US) engaged Danfoss for advanced VFD technology to assist in making the site one of the most energy-efficient cement plants in the world. “It’s well known that variable frequency drives can dramatically cut energy costs in fan applications. For example, if speed can be reduced 20 percent, then kW consumption can be cut up to 50 percent due to the physics of motor Affinity Laws. The critical engineering decision is to select and configure the right kind of VFD for the application,” said Michael Ifurung, electrical engineer at the facility. After careful consideration of VFD suppliers and equipment capabilities, Kendall Walden, Holcim’s electrical and process controls manager, and Ifurung selected Danfoss VLT ® Automation VT Drives, which are designed to handle industrial applications. “These are variable-torque type drives,” Ifurung continues. “At faster speeds, a fan encounters more pressure. That requires more torque to spin the fan. Because torque reductions vary as the cube of speed, every time you can reduce torque you can reduce RPMs. Thanks to Affinity Laws, that means you can cut kW exponentially. That’s how the VLT ® Drives The bottom-line benefit of the VLT ® implementation at the facility was the substantial energy savings. “Everyone knows that anytime you can reduce fan motor RPMs you can get exponential energy savings,” says Walden. “In our case, the results are significant. This technology has aided our overall electrical efficiency. And for the second year in a row, our plant has received EPA’s ENERGY STAR ® for Super Energy Efficiency. Danfoss VLT ® Drives are helping our Ste. Genevieve plant build a solid reputation for saving energy.” | 1-800-432-6367 input #44 at

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