Power phase failure display circuit

When one phase of the three-phase power supply is short of power, the line can not only sound an alarm,
but also determine which phase is short of power based on the indicator light. The three-phase power failure display circuit
is as shown in the figure. Turn on the switch S. Under normal power supply, relay 1
Kl, K2 and I<3 are all closed, the three normally closed contacts are all open, the normally open contacts are all
closed, and the time relays KT1-KT2, indicator lights EL1-EL3 and
Electric bell HA circuit. When a certain phase is short of power, such as I. Phase 1 is short of power, which causes Kl I
to lose power, and its normal contact returns to the closed state. KT2 is powered on and closed. EL1
lights up and HA rings the alarm. After a period of time. When the KT2 delay time is up,
the normally open contact delays closing, causing KT1 to be powered on, and the KT1 normally closed contact
opens instantly, cutting off the power supply of EL1 . After awhile. When the delay time of KT1 is up, its
delay disconnection contact is disconnected, causing KT2 to lose power and release. KT2 normally open contact
is disconnected. KT1 is released when power is lost. KT1 normally closed contact is closed and EL1 lights up,
like this. EL1 will flash and glow. The phase loss alarm indications of L2 and L3 are the same as L1
. Therefore, the person on duty can see which light is on through the electric bell, and then know
which phase is short of power. During the troubleshooting period, the switch S can be turned off, and the bell will
stop alarming and display it to the operator, so that the operator can handle it in time.