Overvoltage limiter in an aircraft electrical power generation system

Abstract

A method of limiting a generator voltage in an overvoltage condition includes the steps of determining an amount of overvoltage of a generator output voltage exceeding a specified voltage and calculating a reference threshold voltage based upon the duration of overvoltage. A switch is modulated according to a voltage error between the output voltage and the reference threshold voltage. The current flow within the generator is interrupted based upon the voltage error to limit the output voltage to a desired voltage.

What is claimed is: 
     
         1 . A method of limiting a generator voltage in an overvoltage condition comprising the steps of:
 a) determining an amount of overvoltage of a generator output voltage exceeding a specified voltage;   b) calculating a reference threshold voltage based upon the duration of overvoltage;   c) modulating a switch according to a voltage error between the output voltage and the reference threshold voltage; and   d) interrupting current flow within the generator based upon the voltage error to limit the output voltage to a desired voltage.   
     
     
         2 . The method according to  claim 1 , wherein step a) includes using point of regulation voltage. 
     
     
         3 . The method according to  claim 1 , wherein step b) includes decreasing the reference threshold voltage as the duration of the overvoltage increases. 
     
     
         4 . The method according to  claim 1 , wherein the switch is arranged between a permanent magnet generator and an exciter, and step d) includes interrupting the current between the permanent magnet generator to the exciter. 
     
     
         5 . The method according to  claim 4 , wherein step d) includes interrupting the current along a return path from the exciter to the permanent magnet generator. 
     
     
         6 . The method according to  claim 1 , comprising step e) tripping an overvoltage protection switch if at least one of a maximum overvoltage is exceeded or a duration of overvoltage condition exceeds allowable limits. 
     
     
         7 . A method of limiting a generator voltage in an overvoltage condition comprising the steps of:
 a) determining an amount of overvoltage of a generator output voltage exceeding a specified voltage;   b) modulating a switch to the specified voltage; and   c) interrupting current flow within the generator based upon the voltage air to limit the output voltage to a desired voltage.   
     
     
         8 . The method according to  claim 7 , wherein the switch is arranged between a permanent magnet generator and an exciter, and step c) includes interrupting the current between the permanent magnet generator to the exciter. 
     
     
         9 . The method according to  claim 8 , wherein step c) includes interrupting the current along a return path from the exciter to the permanent magnet generator. 
     
     
         10 . The method according to  claim 7 , comprising step d) tripping an overvoltage protection switch if at least one of a maximum overvoltage is exceeded or a duration of overvoltage condition exceeds allowable limits.