Circuit using residual magnetism of permanent magnet machine for emergency lighting

Small hydropower stations in rural areas lack backup power sources and emergency lighting devices. Once an accident occurs at night, the small hydropower station will be disconnected from the power grid,
the power supply to the factory will be interrupted, and the workshop will be dark, which will cause difficulties in handling the accident.
    In hydrogenerator units using YT series automatic regulators, permanent magnet generators with speed measurement signal sources can be used for emergency lighting
. The circuit is shown in Figure 7-19.
    When an accident occurs in the power plant and the power supply of the plant is interrupted, the contactor KM connected to the power bus of the plant loses power and is released. Its normally
closed contact closes and the accident lighting is automatically turned on. The person on duty can immediately assist the automatic speed regulator to turn back to "no-load", and then switch the
speed regulator to "manual" mode to maintain the "no-load" operation of the unit to meet the emergency lighting requirements, and at the same time, the fly-pendulum motor can be
taken out of operation. .
    When the power supply of the plant is restored, the contactor KM is electrically closed and its normally closed contact is disconnected. Cut off the accident lighting circuit.