Variable Frequency Drive Package
for the University of Oklahoma Biomedical Research Center

Recently, the University of Oklahoma began construction of a $24 million Biomedical Research Facility. Knowing our abilities, the University called upon us for their Variable Frequency Drive needs.

If set side-by-side, this array of Variable Frequency Drives would extend more than 30 feet across! Not shown in this photo are the 7.5 HP units.

For this project we provided a total of ten VFD packages including:

• Three 125 HP Eaton Cutler-Hammer AF-5000+ Variable Torque Drives (P/N AF-512507-0480) for control of supply fans, designated SF-1, SF-2 and SF-3.
• Three 30 HP Eaton Cutler-Hammer AF-5000+ Variable Torque Drives (P/N AF-503107-0480) for control of various pumps, designated P-3, P-4 and P-5.
• Two 15 HP Eaton Cutler-Hammer AF-5000+ Variable Torque Drives (P/N AF-501507-0480) for control of exhaust fans, designated EF-12A and EF-12B.
• Two 7.5 HP Eaton Cutler-Hammer AF93 Variable Torque Drives (P/N AF93AG0C007D) for control of various pumps, designated P-1 and P-2.

These are the three 125 HP Variable Frequency Drive packages. At 125 HP the components for these packages are so large we installed the control components in a 600 mm wide enclosure and the drive (and its associated disconnect) in an 800 mm wide enclosure. Then we bolted the two enclosures together!

All drives were equipped with a Hand-Off-Auto (HOA) selector circuit. In hand mode, the drive could be started and controlled locally. In automatic mode, the drive is controlled remotely by means of a contact closure. An additional selector switch provided Drive and Bypass Modes. In bypass mode the Variable Frequency Drive could be isolated (to facilitate servicing) and the motor could be started across the line. All drives would follow a 4-20 mA signal for speed control. They generated an additional 4-20 mA signal output for monitoring actual drive speed. They also featured Drive Enabled and Bypass Enabled indication.

Shown here, from left to right, are the three 30 HP packages and two 15 HP packages. Other than component size these are virtually identical in design to the 125 HP packages.

OSCO also provided complete documentation for the project including the following:

• Installation Instructions
• AF-5000+ Drive Manuals
• AF93 Drive Manuals
• Specific Device Information Sheets
• AF-5000+ Drive Schematics
• Panels Documentation
• Dimensioned Drawings
• Electrical Schematics
• Bill of Material

Here you see the internal components of one of the 125 HP packages. In the left enclosure we mounted the VFD and its power disconnect switch. In the right enclosure are the interlocked drive/bypass contactors, motor circuit protector and relays.

Last modified: April 07, 2010

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