9905-756

About the 9905-756

This is an energize-to-trip digital overspeed protection device that utilized three magnetic pickups (MPUs) interfaced with three separate speed-sensing units to continually monitor prime mover speed, sampling prime mover speed every 5 ms. There is a max system response time of 40 ms.

These three units are in a two-out-of-three vote configuration, a hardware vote which occurs after three separate speed calculations have been performed. The 9905-756 system actuates its relay output based on that hardware vote. It is important to note that because this is one of the energize-to-trip models in the ProTech 203, the interposing relay will not actuate if the system loses input power.

The 9905-756 system has all three units enclosed in one, locked enclosure, with access to PROGRAM mode restricted by using a key switch to prevent unauthorized changes or testing. LED indicators on the front panel (one panel per speed-sensing device) provide a quick way to catch when things are not functioning as they should, such as if an MPU has failed, a unit’s CPU is acting up, or a unit has tripped. There are separate LEDs to indicate separate problems, and each speed-sensing unit has its own set of LEDs. Some function errors may also be set to trigger an alarm output when certain conditions are detected.

Woodward ProTech 203 Manual 85196 should be consulted prior to installing the 9905-756 overspeed protection system to ensure all safety precautions are followed and to prevent accidental hardware damage. Additional product specifications can also be found in this manual.