# US 12,768,890 B2 · Generator control relay continuous built-in test circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,768,890 B2 - Document ID: US12768890B2 - Status: Granted - Kind: B2 - Application number: 18/797,092 - Filed: 2024-08-07 - Published: 2026-02-12 - Granted: 2026-10-20 - Earliest claimed: 2024-08-07 - Assignees: Hamilton Sundstrand Corporation - Applicants: Hamilton Sundstrand Corporation - Inventors: Thomas P. Joyce - Web page: https://patentgrep.com/patent/US12768890B2 ## CPC - G01R 31/3278: {of relays, solenoids or reed switches (measuring contact resistance G01R27/205; high voltage magnetic switches G01R31/3271, G01R31/333; testing electric windings G01R31/72; monitoring of fail safe circuits H01H47/002)} - H03K 3/037: Bistable circuits - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract An apparatus may include a controller configured to periodically generate a control signal at a first logic level to initiate a continuous built-in test for a generator control relay (GCR) switch. The apparatus may also include a GCR switch control circuit configured to determine when the GCR switch will not have a current flowing therethrough and generate a GCR switch control signal to open the GCR switch responsive to the control signal. The apparatus may further include a voltage monitoring circuit configured to monitor a voltage across the GCR switch when the GCR switch is opened and compare the monitored voltage to a threshold value. The voltage monitoring circuit is also configured to generate a first output value indicating the GCR switch has passed the continuous built-in test or a second output value indicating the GCR switch has failed the continuous built-in test. ## Claims ### Claim 1 An apparatus for performing a continuous built-in test for a generator control relay (GCR) switch, the apparatus comprising: a controller configured to periodically generate a continuous built-in test (CBIT) control signal at a first logic level to initiate the CBIT for the GCR switch; a GCR switch control circuit configured to determine when to open the GCR switch and to generate a GCR switch control signal to open the GCR switch; and a voltage monitoring circuit configured to: monitor a voltage across the GCR switch when the GCR switch is opened; compare the monitored voltage to a threshold value; and generate a first output value indicating the GCR switch has passed the continuous built-in test responsive to a first comparison result or a second output value indicating the GCR switch has failed the continuous built-in test responsive to a second comparison result. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the GCR switch control circuit is configured to determine when the GCR switch will not have a current flowing therethrough and to generate the GCR switch control signal to open the GCR switch responsive to (i) the CBIT control signal from the controller, (ii) an exciter drive control signal from a generator control circuit, and (iii) a GCR control signal that drives the GCR switch when the GCR switch control circuit is disabled. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the GCR switch control circuit comprises a latch circuit configured to latch a test completion status signal to one of a first logic state indicating a test is incomplete and a second logic state indicating the test is complete, wherein the latch circuit is cleared responsive to the CBIT control signal from the controller going to a second logic level. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the voltage monitoring circuit comprises: a voltage sensing circuit configured to sense the voltage across the GCR switch and to generate a voltage sense signal; and a comparator configured to compare the voltage sense signal with a reference voltage and generate a first logic signal to indicate the GCR switch has passed the continuous built-in test or a second logic signal to indicate the GCR switch has failed the continuous built-in test. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the voltage monitoring circuit comprises a latch circuit configured to latch an output to the first output value responsive to a determination that the GCR switch has passed the continuous built-in test based on a comparison of the voltage across the GCR switch and a reference voltage or latch the output to the second output value indicating the GCR switch has failed the continuous built-in test based on the comparison of the voltage across the GCR switch and the reference voltage. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the determination of when to open the GCR switch is based on: (i) a state of the CBIT control signal from the controller and (ii) a determination of when the GCR switch will not have a current flowing therethrough. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the GCR switch control circuit is further configured to open the GCR switch for a single off switch cycle when an exciter switch associated with the GCR switch is also open. ### Claim 8 An apparatus for performing a continuous built-in test for a generator control relay (GCR) switch, the apparatus comprising: a controller configured to periodically generate a continuous built-in test (CBIT) control signal at a first logic level to initiate the CBIT for the GCR switch; a GCR switch control circuit configured to generate a GCR switch control signal to open the GCR switch responsive to (i) the CBIT control signal from the controller, (ii) an exciter drive control signal from a generator control circuit, (iii) a GCR control signal that can open the GCR switch, and (iv) a CBIT completion status signal that disables the GCR switch control circuit from opening the GCR switch after it has already opened one time for a given test iteration; a first latch circuit configured to latch a test completion status signal to one of a first logic state indicating a test is incomplete and a second logic state indicating the test is complete, wherein the first latch circuit is cleared responsive to the CBIT control signal from the controller going to a second logic level; a voltage sensing circuit configured to sense a voltage across the GCR switch and to generate a voltage sense signal; a comparator configured to compare the voltage sense signal with a reference voltage and generate a first logic signal to indicate the GCR switch has passed the continuous built-in test or a second logic signal to indicate the GCR switch has failed the continuous built-in test; and a second latch circuit configured to latch an output to the first logic signal responsive to the first logic signal from the comparator or latch the output to the second logic signal responsive to the second logic signal from the comparator. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the GCR switch control circuit is configured to be disabled by the controller. ### Claim 10 (depends on 8) The apparatus of claim 8, wherein the second latch circuit is cleared responsive to the CBIT control signal from the controller going to the second logic level. ### Claim 11 (depends on 8) The apparatus of claim 8, wherein the GCR switch control circuit is further configured to open the GCR switch for a single off switch cycle when an exciter switch associated with the GCR switch is also open. ### Claim 12 (depends on 8) The apparatus of claim 8, wherein the GCR switch control circuit comprises: a NAND gate having a first input connected to receive the CBIT control signal from the controller, a second input connected to receive the exciter drive control signal from the generator control circuit, and a third input connected to receive a CBIT completion status signal; an AND gate having a first input connected to an output of the NAND gate, a second input connected to receive the GCR control signal, and an output configured to provide the GCR control signal to open and close the GCR switch; and a third latch circuit configured to generate the CBIT completion status signal responsive to the output of the NAND gate. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the third latch circuit is configured to enable and disable the NAND gate responsive to the CBIT completion status signal. ### Claim 14 (depends on 12) The apparatus of claim 12, further comprising: a GCR drive and isolation circuit configured to drive the GCR switch responsive to the GCR control signal. ### Claim 15 A method for performing a continuous built-in test for a generator control relay (GCR) switch, the method comprising: periodically generating a control signal at a first logic level to initiate the continuous built-in test for the GCR switch using a controller; determining when the GCR switch will not have a current flowing therethrough using a GCR switch control circuit; generating a GCR switch control signal to open the GCR switch responsive to the control signal from the controller using a GCR switch control circuit when the GCR switch does not have the current flowing therethrough; monitoring a voltage across the GCR switch when the GCR switch is opened using a voltage monitoring circuit; comparing the monitored voltage to a threshold value using the voltage monitoring circuit; and generating a first output value indicating the GCR switch has passed the continuous built-in test responsive to a first comparison result or a second output value indicating the GCR switch has failed the continuous built-in test responsive to a second comparison result. ### Claim 16 (depends on 15) The method of claim 15, wherein generating the GCR switch control signal comprises: determining when the GCR switch will not have the current flowing therethrough using the GCR switch control circuit; and generating the GCR switch control signal to open the GCR switch responsive to (i) the control signal from the controller, (ii) an exciter drive control signal from a generator control circuit, and (iii) a GCR control signal that drives the GCR switch when the GCR switch control circuit is disabled. ### Claim 17 (depends on 15) The method of claim 15, further comprising: disabling the GCR switch control circuit using the controller. ### Claim 18 (depends on 15) The method of claim 15, further comprising: latching an output of the voltage monitoring circuit to the first output value using a latch responsive to a determination that the GCR switch has passed the continuous built-in test based on a comparison of the voltage across the GCR switch and a reference voltage or to the second output value responsive to a determination that the GCR switch has failed the continuous built-in test based on the comparison of the voltage across the GCR switch and the reference voltage. ### Claim 19 (depends on 18) The method of claim 18, further comprising: clearing the latch responsive to the control signal from the controller going to a second logic level. ### Claim 20 (depends on 15) The method of claim 15, further comprising: opening the GCR switch for a single off switch cycle when an exciter switch associated with the GCR switch is also open.