9905-994

About the 9905-994

In the Woodward line of ProTech 203 Overspeed Protection Systems, model 9905-994 offers several features that make it a sound choice for your overspeed protection applications. This de-energize-to-trip device is designed to allow hot replacement of individual speed-sensing units, of which there are three. These units can also be individually tested without taking the prime mover offline, and a trip of only one unit will not stop the operation of the system overall.

Each unit must be reset before the turbine is started, as well as after a trip. Model 9905-994 has a remote reset feature, so units may be reset from a location away from the device itself.

The three speed-sensing units in ProTech model 9905-994 are nearly identical. They are all designed to operate the same way, monitoring prime mover speed using magnetic pickups (MPUs), performing independent speed calculations, and performing a hardware two-out-of-three vote with the other two units. The only difference between the three units is the power supplies. There is a separate power supply for each unit, a 120 Vac/dc supply for each unit A and B, and a 220 Vac power supply for unit C.

Each unit also has an identical operator interface, located on the front panel of the IP65-certified enclosure. Key features of these interfaces include:

• Two-line LCD
• Keypad
• LED functional status indicators
• Alarm output
• Potentiometer

Because the units are designed to operate independently prior to the hardware vote, they must be programmed separately. It is important that they be programmed with identical parameters though. Woodward manual 85196 has full details on programming model 9905-994 as well as additional product specifications.