Three terminal bridged t network for monitoring the operating speed of a motor

Claim 1

MEANS FOR MONITORING THE OPERATING SPEED OF AN ELECTRIC MOTOR NORMALLY OPERATNG AT A SELECTED MAXIMUM SPEED RELATIVE TO THE FREQUENCY OF AN ALTERNATING CURRENT SOURCE, SAID MOTOR BEING OF A TYPE INCLUDING A MAIN FIELD WINDING, AN AUXILIARY FIELD WINDING IN SERIES WITH A PHASE SHIFTING CAPACITOR ENERGIZED THROUGH A PAIR OF INPUT CONDUCTORS LEADING FROM SAID ALTERNATING CURRENT SOURCE, ONE OF SAID INPUT CONDUCTORS LEADING TO A CONDUCTOR CONNECTING THE AUXILIARY AND MAIN FIELD WINDINGS, AND ANOTHER OF SAID INPUT CONDUCTORS LEADING TO A CONDUCTOR CONNECTING SAID MAIN FIELD WINDING AND SAID PHASE SHIFTING CAPACITOR; SAID MONITORING MEANS COMPRISING A BRIDGE T NETWORK INCLUDING SAID AUXILIARY FIELD WINDING IN A FIRST ARM THEREOF AND SAID PHASE SHIFTING CAPACITOR IN A SECOND ARM THEREOF, A RESISTOR ELEMENT AND AN AUXILIARY CAPACITOR ELEMENT SERIALLY CONNECTED ACROSS ONE OF SAID ARMS OF THE BRIDGED T NETWORK, THE RESISTOR ELEMENT BEING CONNECTED TO THE PHASE SHIFTING CAPACITOR AND THE AUXILIARY CAPACITOR BEING CONNECTED TO THE AUXILIARY WINDING, ONE OF SAID SERIALLY CONNECTED ELEMENTS PROVIDING A THIRD ARM OF THE BRIDGED T NETWORK, A PAIR OF SIGNAL OUTPUT CONDUCTORS EXTENDING FROM SAID BRIDGE T NETWORK, ONE OF SAID PAIR OF OUTPUT CONDUCTORS LEADING FROM A CONDUCTOR SERIALLY CONNECTING SAID SERIALLY CONNECTED ELEMENTS, AND THE OTHER OF SAID PAIR OF OUTPUT CONDUCTORS BEING COMMON TO SAID INPUT CONDUCTOR CONNECTED TO THE MAIN FIELD WINDING AND THE ARM OF SAID BRIDGED T NETWORK OTHER THAN THE ONE ARM ACROSS WHICH SAID RESISTOR AND AUXIALIARY CAPACITOR ELEMENTS BE SERIALLY CONNECTED, AND ELECTRICAL CONDITION RESPONSIVE MEANS OPERATIVELY CONNECTED TO SAID PAIR OF OUTPUT CONDUCTORS, SAID RESISTOR ELEMENT AND CAPACITOR ELEMENT BEING SO RELATED TO THE FIRST AND SECOND ARMS OF THE BRIDGED T NETWORK THAT SAID NETWORK MAY BE SUBSTANTIALLY BALANCED UPON OPERATION OF SAID ELECTRIC MOTOR AT SAID SELECTED MAXIMUM SPEED, AND UPON THE MOTOR OPERATING AT A SLOWER SPEED THAN SAID SELECTED MAXIMUM SPEED, THE IMPEDANCE OF THE AUXILIARY FIELD WINDING OF SAID MOTOR MAY BE EFFECTIVELY CHANGED SO AS TO SUBSTANTIALLY UNBALANCE THE FIRST ARM OF THE BRIDGED T NETWORK RELATIVE TO THE SECOND AND THIRD ARMS THEREOF, WHEREUPON THE ELECTRICAL CONDITION RESPONSIVE MEANS BECOMES EFFECTIVE AT SAID SLOWER SPEED CONDITION OF THE MOTOR.