Total Power Quality and Its Impact on Machinery Availability

An often overlooked element of overall equipment effectiveness comes in the form of poor power quality

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As for power conversion, in a processing or packaging environment there are critical power loads that warrant full protection. For example, a critical piece of machinery on the plant floor that would dramatically impact productivity if it were to shut down unexpectedly due to a power outage. This type of machinery requires an uninterruptible power supply (UPS) system capable of handling the load on its own for a reasonable period of time to perform a controlled shut down; limit scrap and enable faster restart of production. Several UPS topologies or types exist depending on production environment run-times and needs.

Online double conversion UPS systems provide critical machinery with the highest level of protection by isolating that machinery from raw utility power. It converts the input AC electricity from AC to DC and then back to fresh AC. If the power supply fails it is supplied directly from the UPS batteries.

This topology differs from a standby UPS, also called an “offline UPS,” which is the most common type of UPS found in a computer or office supply store. It draws current from the AC and switches to battery within a few milliseconds after detecting a power failure. The line interactive UPS “interacts” with the AC power line to smooth out the waveforms and correct the rise and fall of the voltage. By contrast, the online UPS inverter is always on so that all incoming power is converted to direct current, which both fills up the batteries and feeds the inverter and provides more protection. Depending on the complexity of the controls, run-time and the amount of a control shut-down required, OEMs can decide which topology will work best for their application needs.

The Power of Protection

In the world of manufacturing, machine downtime is an ugly word. But it doesn’t have to be something you deal with in the dark. OEE metrics can measure the impact of downtime on each piece of equipment that’s integral to the manufacturing processes. Once the OEE score is established and tracked, the end users—perhaps with a little help from the OEM—should investigate how power quality may be degrading the three ratios that make-up OEE: availability, productivity and quality. Focusing on availability and employing power quality devices in a multi-stage design as recommended by the IEEE is critically important to reducing and eliminating future downtime and improving OEE and the bottom line.

ABOUT THE AUTHOR: Mark Dziedzic is the Senior Product Marketing Manager for Sola HD at Emerson.