Allen-Bradley 810-AO9A Inverse Time Relay

Allen-Bradley 810-AO9A Inverse Time Relay is a legacy inverse-time current relay from Allen-Bradley’s Bulletin 810 family, designed to deliver time-delayed tripping proportional to overload current in protection schemes. In operation, current above a preset threshold initiates a controlled delay before the relay releases, enabling coordinated protection with other devices in motor, feeder, or distribution circuits. The Bulletin 810 family uses mechanical timing via a dashpot assembly, with variants associated to Series A or Series B configurations; timing behavior is set by this dashpot arrangement rather than electronic components. Ideal for classic protection schemes where inverse-time characteristics are required, the 810-AO9A supports coordination by allowing faster trips for higher currents while providing longer delays at lower overloads, reducing nuisance trips in multi-device protection schemes. Note that exact specifications (input current ranges, trip thresholds, coil voltages, and mounting details) are model-dependent, so consult an official Allen-Bradley listing or datasheet for this suffix to verify compatibility with existing relay and control hardware.