Product Description

ProTech model 9907-146 has three speed-sensing units that act independently to monitor prime mover speed and perform speed calculations. Speed is monitored using magnetic pickups (MPUs). This overspeed protection device is susceptible to electromagnetic interference and must be installed in a location protected from high-voltage and high-current devices.

In a total response time of 40 ms or less, speed-sensing units A, B, and C sample prime mover speed perform independent speed calculations, then activate a trip relay if a two-out-of-three hardware vote determines overspeed conditions have been met.

The present speed of an individual unit is the default display on that unit’s operator interface LCD. Additional parameters can be viewed by cycling through using the keypad on the interface. The peak speed of each unit is updated each time the present speed exceeds the previously recorded peak speed during an overspeed condition. When this happens, the new peak speed is updated and stored in non-volatile memory.

9907-146 units are in a locked enclosure that is NEMA 4 and 4X certified (IP54 for Europe). A key lock prevents unauthorized personnel from accessing programming or testing functions.

Individual units can be tested or replaced without tripping the prime mover. The two-out-of-three-vote configuration permits two of the three units to maintain control of the system and provide accurate outputs. This is also made possible by each unit having its own 24 Vdc power supply.

Additional features of ProTech model 9907-146 are:

• Remote reset
• Alarm outputs
• LED functional status indicator – separate LEDs for MPU failure, CPU failure, tripped unit
• Built-in self-test
• MPU Fail Timer

Woodward Manual 85204 (G) has complete details on each of these features, tunable parameters, and safety precautions for model 9907-146. Because this is an energize-to-trip overspeed protection model, a prime mover trip is not guaranteed to occur from loss of power.