Product Description

Model 9905-990 has several features that make it an efficient choice of overspeed protection device. These three units, A, B, and C are identical speed-sensing units that can be tested or even replaced individually. ProTech model 9905-990 uses a two-out-of-three hardware voting configuration, so the overall system can remain in operation with at least two units online.

Prior to the hardware voting relay, the three units act independently to monitor prime mover speed (sampled every 5 ms) using magnetic pickups (MPUs) and perform a speed calculation. A trip relay is activated if an overspeed condition is met. The total response time of this process is a maximum of 40 ms.

The 9905-990 device has a speed-sensing frequency range of 100 Hz to 32 kHz and a trip-point frequency range of 250 Hz to 25 kHz. This system has an accuracy rating of 0.05% of point + 2 Hz over the operating temperature and should be installed in a location where it is protected from things such as electromagnetic interference, and vibration and in a space where there is adequate ventilation for cooling.