Fault detection apparatus

Claim 1

Fault detection and monitoring apparatus for use with an electric circuit which controls the operation of an instrumentality and includes a plurality of electrically operable devices which are operable in electrical current conducting and non-conducting conditions and must operate in a predetermined manner to establish a predetermined circuit condition, said devices being adapted to be connected with a source of electric alternating current power, said apparatus comprising: electrically operable detecting means for detecting the condition of said devices including an input circuit coupled to each of said devices and said source of electric power and an output circuit providing a continuous electrical output signal when any one of said devices is in said non-conducting condition; and monitoring means responsive to the continuous electrical output signal of said detecting means for comparing the value of said continuous signal with a predetermined value and indicating whether said devices are operating in said predetermined manner; said detecting means comprising: transformer means, having primary winding means and secondary winding means for coupling said electrically operable devices and said source of power to said monitoring means, said primary winding means being adapted to be connected to said source of power and connected in parallel circuit relation with said devices; and rectifier circuit means connected to said secondary winding means to rectify the signal coupled to said secondary winding means and provide said continuous signal; said monitoring means being connected to said rectifier circuit means to be energized by said continuous signal.