9905-975

About the 9905-975

Each of the three speed-sensing units that make up the 9905-975 overspeed protection system has its own 24 Vdc power supply and its own front panel operator interface.

Speed-sensing units A, B, and C activate two voter relays each, which change state in the event an overspeed condition is detected. These units are connected in a two-out-of-three voting configuration. This modular design helps prevent an inadvertent trip, acts as a safeguard if one of the units goes offline (two units will maintain control and continue providing an accurate output), and allows for things such as hot replacement.

Model 9905-975 is one of the energize-to-trip versions in this Woodward ProTech 203 series. During normal operation, the voter relays are in a de-energized state. Because this is an energize-to-trip model, it must have a cold-coil monitoring device wired into it if it is to meet the API 612 overspeed trip specifications.

The enclosure of the 9905-975 overspeed protection device meets IP 65 standards. To prevent unauthorized access to programming and testing features, this enclosure is locked.

Programming is done through each unit’s operator interface, located on the front panel of the 9905-975 device. Complete programmable parameters and instructions can be found in Woodward ProTech 203 manual 85195. The LCD on each unit’s interface is also where operators can view error codes. Along with an error code display, some errors are also indicated with an LED and an alarm output.