Water pump motor anti-rundown protection circuit

If the water pump drains the water from the well and the water pump is still
running, it will not only waste electricity, but also may burn the motor
. The circuit in Figure 5-17 can avoid this situation.
The circuit uses TWH8778 power switch integrated circuit A
and photocoupler B as control components . When the water in the well
is drained, A is cut off, the triac V is
closed, the relay KA is released, and the water pump stops running.