9905-978

About the 9905-978

Woodward ProTech 203 model 9905-978 uses three magnetic pickups (MPUs) to monitor for overspeed conditions. There are three MPUs in this system, each interfaced with a separate speed-sensing unit. A trip relay is activated if an overspeed condition is detected by two of the three units. If the condition is detected by only one unit, only that unit will trip. Units remain tripped until they are reset or until the power is cycled.

Units A, B, and C are all enclosed in the same locked enclosure, an enclosure that meets IP 65 and NEMA 4 standards. Each unit in this de-energize-to-trip ProTech 203 model comes with its own 24 Vdc power supply.

Model 9905-978 has several features that make it an efficient overspeed protection device choice.

• The modular design and two-out-of-three voting configuration permit hot replacement
• Total system response time is 40 ms max (speed is sampled every 5 ms)
• Separate operator interface for each speed-sensing unit
• Each unit can be reset from a remote location
• LEDs and alarm outputs alert of trouble with a unit
• Error codes displayed on each unit’s interface LCD permit faster troubleshooting

There is a separate alarm output and LED to indicate a tripped speed-sensing unit. Several conditions might cause an individual unit to trip. Details may be found in Woodward ProTech 203 manual 85195.

Model 9905-978 has nine tunable parameters. These are programmed by accessing the system’s PROGRAM mode, which requires unlocking the enclosure to prevent unauthorized changes. Programming of the 9905-978 units is done individually through that unit’s keypad and LCD, but all three units must be set with the same trip points for the system to operate correctly.