9905-998

About the 9905-998

Magnetic pickups (MPUs) monitor prime mover speed in this Woodward ProTech overspeed protection model. Each one is interfaced with a different speed-sensing unit, units A, B, and C. These MPUs can be set to a Failed Set Point range of 100 rpm to 25,000 rpm, and a Failed Timeout range of 1 second to 533 minutes 20 seconds.

The MPUs and three speed-sensing units sample prime mover speed every 5 ms. If a hardware two-out-of-three vote determines an overspeed condition is met, a trip relay is activated. The total response time for this de-energize-to-trip system is a maximum of 40 ms. Units A, B, and C are in a locked enclosure, that is NEMA 4X certified when the optional stainless steel hubs are used. Each unit has its own 24 Vdc power supply.

ProTech model 9905-998 has many features, including:

• Hot replacement – individual units may be replaced without taking the prime mover offline
• Built-in self-test – individual units may be tested while the prime mover is online
• Operator interfaces – one per speed-sensing unit
• LED indicators – separate LEDs to indicate a unit trip, MPU failure, or failed CPU
• Remote reset – Units A, B, and C may be reset from a remote location
• Restricted access to PROGRAM mode – units are switched between MONITOR mode and PROGRAM mode by using a key switch that is located inside the locked enclosure

Woodward ProTech manual 85196 has full details on the features of overspeed protection model 9905-998, including all of the functions achieved through the operator interface keypad and LCD.