9905-753

About the 9905-753

Product 9905-753 is a digital overspeed protection device. This is a de-energize-to-trip device that has three nearly identical speed-sensing units to monitor prime mover speed and activate a trip relay in the event of overspeed detection. The only difference among the units is that two of them have a 120 Vac/dc voltage input and the third unit has a 220 Vac voltage input. Each unit has its own power supply and the system can be configured for compatibility with various power sources.

The modular design of this system permits a number of functions preventing overall system failure or system downtime. The 9905-753 system has a two-out-of-three voting configuration based on three separate speed calculations. A built-in frequency generator makes it possible to test speed-sensing units one at a time while the prime mover is online. If any one of the three units trips, the other two will maintain normal operations. This also means that a single unit can be replaced without disrupting operations

A key switch is used to move between MONITOR and PROGRAM modes. The 9905-753 system will run while in either of these two modes however it should be left in MONITOR mode unless the units are actually being programmed. Tunable parameters are: MPU failed timeout, MPU gear teeth, MPU failed setpoint, trip speed setpoint, and trip on MPU failure.

Product 9905-753 has a functional status LED indicators and alarm outputs to alert operators of any errors within the system. Error codes and troubleshooting guidelines may be found online in Woodward ProTech 203 Overspeed Protection System Manual 85196.