Fault signal trip circuit

Shown is the circuit breaker accident trip signal circuit . It consists of intermediate relay KV, buzzer HA, test button SB1, release
button SB2, etc. The circuit between the accident audio busbars WS1 and WS2 is the accident audio
starting circuit. QF is the normally closed auxiliary contact of the circuit breaker . When the circuit breaker is closed, the normally
closed auxiliary contact opens.
    When the circuit breaker accidentally trips, its normally closed auxiliary contact QF recovers (that is, 6jj is closed). The buzzer
HA forms a closed circuit through FU1, the moving contact of the intermediate relay KV, the two
pairs of contacts of the control switch SA, and the circuit breaker auxiliary contacts QF and FU2, and sends out an accident audio
signal .
    After the person on duty heard this, he pressed the sound release button SB2, so the intermediate relay
KV was energized (WS-I-FU1-KV coil-SB2-FU2-WS), and its normally open
contact was closed, and the moving contact was closed. KV, the two pairs of contacts of the control switch SA,
the normally closed auxiliary contact of the circuit breaker QF, and FU2 form a self-locking circuit. At the same time, the normally closed movable contact of the intermediate relay KV opens, the buzzer circuit is cut off
, and the sound is released.
    SB1 is the audio test button. Press SB1, the buzzer HA is powered on and makes a sound. The energizing circuit of buzzer HA- is: FU1— normally closed contact
of HA intermediate relay KV —SB1—FU2. SB1 is used for daily testing of audio circuits.