9905-879

About the 9905-879

Two-out-of-three voting, a hot replacement feature, and a built-in self-test feature provide continuous, reliable overspeed protection from this ProTech 203 model. As long as two of the three 9905-879 speed-sensing units are operational, the prime mover can stay online. Two units will still provide an accurate output.

This output is the result of a two-out-of-three vote based on the calculations of each of the three units, each with its own magnetic pickup (MPU). A trip relay is activated if overspeed conditions are detected. A single tripped unit will not inadvertently cause a turbine trip. Several conditions may be to blame for a tripped unit, such as MPU or CPU failure, and manual 85191(version B) should be consulted for a comprehensive troubleshooting guide.

Model 9905-879 is one of the de-energize-to-trip models in this Woodward overspeed protection system series. This is one of the models with a 120 Vac/dc power supply for each of the system’s three speed-sensing units. The speed-sensing frequency range of model 9905-879 is 100 Hz to 32 kHz, and the trip-point frequency range is 250 Hz to 25 kHz.

The speed-sensing units of ProTech 203 model 9905-879 are all in a single closure. If the optional stainless steel hubs are used, the enclosure meets NEMA 4X certification standards.