About the 9907-084
A system-wide trip relies on an overspeed detection from two of the three individual speed-sensing units in model 9907-084. A single-tripped unit will not take the prime mover offline. Hot replacement and testing of the units while the system is running are a few of the features enabled by this two-out-of-three voter relay configuration. Devices in this series use magnetic pickups to monitor prime mover speed, perform three separate speed calculations, and activates a trip relay in the event of an overspeed condition detection.
ProTech 9907-084’s speed-sensing units, each with their own 120 Vac/dc power supply are in a single key locked, IP 65 certified enclosure. On the front panel of this enclosure is an operator interface for each unit.
Five tunable parameters are set using the LCD and keypad on each interface. Trip Speed Set Point, Trip on MPU Failure, MPU Failed Timeout, MPU Failed Set Point and MPU Gear Teeth are programmed for each speed-sensing unit individually, though they must be set for identical trip points. Woodward ProTech Manual 85203 has full programming details as well as a programming worksheet to assist with this step.