Contactor health monitor circuit and method

Abstract

In one possible embodiment, a contactor health monitor circuit is provided having a first operational amplifier connected at a first input to a line one primary side terminal of a contactor and connected at a second input to a line two primary side terminal of the contactor. The circuit also includes a second operational amplifier connected at a first input to a line one secondary side terminal of the contactor and connected at a second input to a line two secondary side terminal of the contactor. A summing amplifier is connected at a first input to an output of the first operational amplifier summed with an output of the second operation amplifier.

What is claimed is: 
     
         1 . A contactor health monitor circuit comprising:
 a) a first diode connected at a terminal end to a line one primary side terminal of a contactor;   b) a second diode connected at a terminal end to a line two primary side terminal of the contactor;   c) a third diode connected at a terminal end to a line one secondary side terminal of the contactor;   d) a fourth diode connected at a terminal end to a line two secondary side terminal of the contactor;   e) an operational amplifier circuit;   f) the first diode and the second diode being connected together so as to provide a summed output of the line one primary side contactor terminal and the line two primary side contactor terminal to a first input of the operational amplifier circuit; and   g) the third diode and the fourth diode being connected together so as to provide a summed output of the line one secondary side contactor terminal and the line two secondary side contactor terminal to a second input of the operational amplifier circuit.   
     
     
         2 . The contactor health monitor circuit of  claim 1 , wherein the first diode and the second diode are connected together so the signals from the line one primary side terminal and the line two primary side terminal combine without canceling. 
     
     
         3 . The contactor health monitor circuit of  claim 1 , wherein the third diode and the fourth diode are connected together so the signals from the line one secondary side terminal and the line two secondary side terminal combine without canceling. 
     
     
         4 . The contactor health monitor circuit of  claim 1 , wherein an output of the operational amplifier circuit is connected to an A/D converter input. 
     
     
         5 . The contactor health monitor circuit of  claim 1 , wherein the first diode and the second diode are connected together so the signals from the line one primary side terminal and the line two primary side terminal combine without canceling, and wherein the third diode and the fourth diode are connected together so the signals from the line one secondary side terminal and the line two secondary side terminal combine without canceling. 
     
     
         6 . The contactor health monitor circuit of  claim 4 , wherein an output of the operational amplifier circuit is connected to an A/D converter input. 
     
     
         7 . A contactor health monitor circuit comprising:
 a) a first operational amplifier connected at a first input to a line one primary side terminal of a contactor and connected at a second input to a line two primary side terminal of the contactor;   b) a second operational amplifier connected at a first input a line one secondary side terminal of the contactor and connected at a second input to a line two secondary side terminal of the contactor; and   c) a summing amplifier having a first input connected to receive a sum of an output of the first operational amplifier and an output of the second operation amplifier.   
     
     
         8 . The contactor health monitor circuit of  claim 7 , wherein the summing amplifier has a second input connected to a reference voltage. 
     
     
         9 . The contactor health monitor circuit of  claim 7 , wherein the second input of the first operational amplifier is connected to a reference bias voltage. 
     
     
         10 . The contactor health monitor circuit of  claim 7 , wherein the second input of the second operational amplifier is connected to a reference bias voltage. 
     
     
         11 . The contactor health monitor circuit of  claim 7 , wherein the output of the summing amplifier is connected to an A/D converter input. 
     
     
         12 . The contactor health monitor circuit of  claim 7 , wherein the summing amplifier has a second input connected to a reference voltage, and wherein the second input of the first operational amplifier is connected to a reference bias voltage, and wherein the second input of the second operational amplifier is connected to a reference bias voltage. 
     
     
         13 . The contactor health monitor circuit of  claim 7 , wherein the output of the first operational amplifier is connected to an A/D converter input, wherein the output of the second operational amplifier is connected to an A/D converter input, and wherein an output of the summing amplifier is connected to an A/D converter input. 
     
     
         14 . The contactor health monitor circuit of  claim 13 , comprising:
 a) wherein the first input of the first operational amplifier is connected via resistors and a diode overvoltage protection circuit to the line one primary side terminal of the contactor;   b) wherein the second input of the first operational amplifier is connected via resistors and a diode overvoltage protection circuit to the line two primary side terminal of the contactor, and connected to a reference bias voltage;   c) wherein the first input of the second amplifier is connected via resistors and a diode overvoltage protection circuit to the line one secondary side terminal of the contactor; and   d) wherein the second input of the second amplifier is connected via resistors and a diode overvoltage protection circuit to the line two secondary side terminal of the contactor, and connected to a reference bias voltage; and.   e) wherein the summing amplifier has a second input connected to a reference voltage.   
     
     
         15 . The contactor health monitor circuit of  claim 7 , wherein the summing amplifier has a second input connected to a reference voltage, and wherein the second input of the first operational amplifier is connected to a reference voltage, and wherein the second input of the second operational amplifier is connected to a reference voltage, and wherein the output of the first operational amplifier is connected to a first A/D converter input, wherein the output of the second operational amplifier is connected to a second A/D converter input, and wherein an output of the summing amplifier is connected to a third A/D converter input. 
     
     
         16 . The contactor health monitor circuit of  claim 15 , comprising:
 a) an overvoltage protection circuit connected between the line one primary side terminal of the contactor and the first input of the first operational amplifier;   b) an overvoltage protection circuit connected between the line two primary side terminal of the contactor and the second input of the first operational amplifier;   c) an overvoltage protection circuit connected between the line one secondary side terminal of the contactor and the first input of the second operational amplifier; and   d) an overvoltage protection circuit connected between the line two secondary side terminal of the contactor and the second input of the second operational amplifier.   
     
     
         17 . The contactor health monitor circuit of  claim 7 , comprising:
 a) an overvoltage protection circuit connected between the line one primary side terminal of the contactor and the first input of the first operational amplifier;   b) an overvoltage protection circuit connected between the line two primary side terminal of the contactor and the second input of the first operational amplifier;   c) an overvoltage protection circuit connected between the line one secondary side terminal of the contactor and the first input of the second operational amplifier; and   d) an overvoltage protection circuit connected between the line two secondary side terminal of the contactor and the second input of the second operational amplifier.   
     
     
         18 . A contactor health monitor circuit comprising:
 a) a first operational amplifier having a first input connected to receive a signal from a line one primary side terminal of a contactor, and having a second input connected to receive a signal from a line two primary side terminal of the contactor;   b) a second operational amplifier having a first input connected to receive a signal from a line one secondary side terminal of the contactor, and having a second input connected to receive a signal from a line two secondary side terminal of the contactor;   c) a summing amplifier having a first input connected to receive an output signal from the first operational amplifier summed with an output signal from the second operation amplifier, the summing amplifier having a second input connected to receive a signal from a reference voltage.   
     
     
         19 . The contactor health monitor circuit of  claim 18 , comprising:
 a) an overvoltage protection circuit connected between the line one primary side terminal and the first input of the first operational amplifier;   b) an overvoltage protection circuit connected between the line two primary side terminal and the second input of the first operational amplifier;   c) an overvoltage protection circuit connected between the line one secondary side terminal and the first input of the second operational amplifier; and   d) an overvoltage protection circuit connected between the line two secondary side terminal of the contactor and the second input of the second operational amplifier.   
     
     
         20 . The contactor health monitor circuit of  claim 19 , comprising:
 a) a bias voltage connection at one of the first input of the first operational amplifier or the second input of the first operational amplifier; and   b) a bias voltage connection at one of the first input of the second operational amplifier or the second input of the second operational amplifier.   
     
     
         21 . The contactor health monitor circuit of  claim 18 , wherein the first input of the first operational amplifier is connected via resistors and a diode overvoltage protection circuit to the line one primary side terminal of the contactor, and wherein the second input of the first operational amplifier is connected via resistors and a diode overvoltage protection circuit to the line two primary side terminal of the contactor, and wherein the first input of the second amplifier is connected via resistors and a diode overvoltage protection circuit to the line one secondary side terminal of the contactor, and wherein the second input of the second amplifier is connected via resistors and a diode overvoltage protection circuit to the line two secondary side terminal of the contactor.