9905-884

About the 9905-884

Model 9905-884 uses magnetic pickups (MPUs) to sample prime mover speed every 5 ms and monitor for overspeed conditions. If conditions are met, it results in a trip relay. The 9905-884 system is one of the ProTech 203 series energize-to-trip models. Operators can enjoy peace of mind with the 0.1% (at 25 °C) accuracy rating and two-out-of-three voting configuration design of this system.

Speed-sensing units A, B, and C in models 9905-884 are identical. Each has an operator interface and a 24 Vdc power supply. System programming is done through the operator interface, which has an LCD and keypad. To prevent unauthorized changes, access to PROGRAM mode and the testing functions is restricted with a key switch. Each interface also has LED indicators and alarm output to alert operators when a tripped unit, MPU failure, CPU failure, and more.

Each of the three units must be reset before the turbine is started. Individual units must be reset after they trip (no reset is necessary if the power is cycled). Model 9905-884 has a remote reset feature, making this an easier process.

Present Speed and Peak Speed can both be viewed on a unit’s LCD. Peak Speed is updated each time an overspeed condition occurs if that speed exceeds the previously recorded peak speed. If the new peak speed is the result of an overspeed condition (as opposed to a test), it is stored in non-volatile memory.

A full list of the parameters that can be displayed on the LCD can be found in ProTech 203 Manual 85191 (version B). This manual also contains installation instructions and requirements and should be reviewed before installing models 9905-884. The enclosure for this model has optional stainless steel hubs. When these are used the enclosure meets NEMA 4X standards.