188.8.131.52 Periodic Self-Test
At system power up, the self-test starts after 60 cycles of power line signal, and retests within 60 cycles if the first self-test fails. Five consecutive self-test fails drive the SCR and assert the ALARM signal blinking at 1-second intervals (for 60-Hz systems). After the first self-test pass, the device fires ALARM for 250-ms period to indicate the successful pass of the first self-test. During normal operating conditions, the self-test repeats every 180 cycles. Figure 10 shows the periodic self-test sequences and decision blocks. The device requires one cycle from the AC power line to complete the periodic self-tests listed below:
- Ground Fault Test: the AFE3010 generates a fault current through the FT pin. The device reads a test pass if the AFE3010 detects the fault current through the transformer. If the fault current is not detected, the device reads a test fail. This fail event triggers another self-test within next 60 cycles. After five consecutive fails, the AFE3010 fires the SCR and sets the ALARM blinking at 1-s intervals (for 60-Hz systems). The ground fault test covers the integrity check of the transformer, fault current generator components, feedback resistors, and the AFE3010 fault detection circuits.
- SCR Integrity Test: The AFE3010 performs SCR integrity test after completing the ground fault test. The device induces a SCR anode signal transition with the help of SCR_TST pin. If the SCR anode signal low transition is not detected, the AFE3010 reads a test fail. This fail event triggers another self-test within next 60 cycles. After five consecutive fails it fires the SCR and sets ALARM blinking at 1-s intervals (for 60-Hz systems).