9905-999

About the 9905-999

Product model 9905-999 is a 120 Vac/dc overspeed protection device. This is a Woodward ProTech de-energize-to-trip model that determines trip relay state by way of a two-out-of-three vote performed by this model’s three speed-sensing units. These units monitor prime mover speed with magnetic pickups (MPUs).

This overspeed protection system has a trip-point frequency range of 250 Hz to 25 kHz. The speed-sensing frequency range is 100 Hz to 32 kHz.

Units are programmed using the three operator interfaces on the front panel of model 9905-999. There is one interface per speed-sensing unit, each one with its own LCD, keypad, LED indicators, and potentiometer knob.

The three units within the model 9905-999 system are identical. They are connected in a two-out-of-three voting configuration, meaning it takes an overspeed detection from at least two of the units to prompt a trip relay to take operations offline. Any unit will trip if it detects an overspeed condition, but no single unit will trip the entire system.

A benefit to this design is that this overspeed protection device can handle hot replacement of an individual unit. As long as the other two are online and properly functioning, the system will remain online and provide an accurate output. This also permits the built-in self-test feature, since model 9905-999 will operate with two units in control.

For full feature information, please refer to Woodward ProTech 203 Overspeed Protection System manual 85196.