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Machine Design

HVAC AC Drives

Allen-Bradley PowerFlex 400 HVAC ac drives, rated up to 350 hp, have built-in network connections for building automation systems.

An RS-485 communications interface supports networks that include Modbus RTU, N2, and Siemens P1-FLN. These protocols require no additional hardware or software. Optional modules connect to LonWorks and BACnet networks. A PID controller adjusts the output frequency to maintain a process variable. Three programmable skip frequencies and bands keep the drive from running at resonant speeds. Selectable fan and pump curves provide reduced voltage patterns for centrifugal fan and pump loads. A sleep function cycles off when system demand drops below a preset level, and restarts when demand rises. Users can connect drives to fire and safety systems via freeze/fire and purge inputs. NEMA/UL packaging options meet indoor and outdoor requirements.

Rockwell Automation,
1201 S. Second St., Milwaukee, WI 53204,
(414) 382-2000,

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