CONTROL SYSTEM FOR VARIABLE PITCH AXIAL FAN

摘要

The disclosed system detects the pressure rise across the fan and the flow rate in the system and integrates signals corresponding thereto, and outputs a signal to indicate to the user when the pressure rise exceeds a given level for a corresponding flow rate to warn of a condition within a given degree of a stall condition. The system outputs another signal to block any increase in fan blade pitch and substitutes a decrease pitch signal in response to a predetermined closer approach to a stall condition so that the pitch of the blades is reduced to a position in which the pressure rate rise and flow rate are reduced to a safe level with respect to a stall condition. The system also includes means responsive to the predetermined closer approach to stall to prevent the user from feeding a blade pitch increase signal following a reduction in the pressure rise across the fan until the user resets a bistable device.