9905-991

About the 9905-991

ProTech de-energize-to-trip model 9905-991 comes in an IP65-certified enclosure. There are three individual, identical speed-sensing units in this enclosure, which all come with their own 220 Vac power supply. Within the enclosure is a key switch that is connected to all three units and is used to switch between MONITOR and PROGRAM modes. The enclosure is locked to restrict access to programming and testing functions.

On the front panel of the enclosure are three identical operator interfaces, one for each of the three units. These interfaces all have LED indicators, a two-line LCD, a keypad, and a potentiometer. 9905-991 parameters are set using this interface when the units are in PROGRAM mode. Parameters, error codes, and other system information can be viewed on the LCD when the system is in MONITOR mode.

Due to the modular design of model 9905-991, the three speed-sensing units are programmed individually. They must, however, be programmed identically for proper functioning. Model 9905-991 is part of the ProTech 203 Overspeed Protection System series by Woodward. The ProTech manual 85196 has complete information on the tunable parameters of this device. The manual also contains a programming worksheet to assist with this step.

The modular design is also what permits some key features of this system. Units A, B, and C are in a two-out-of-three-vote configuration. This allows the prime mover to remain online and operations to continue even if one of the units is taken offline, whether it is being tested, replaced, or it trips. A system-wide trip relay is only activated when two of the three units detect overspeed conditions.