Relay Control System of Diesel Generator Set

Sep. 23, 2021

There are three main automatic control systems for diesel generator sets: relay control system and programmable logic controller (PLC).


Relay control system in the automatic control system of diesel generator set: the relay control system is composed of diesel generator, AC brushless synchronous generator and control panel. The diesel generator is equipped with actuators such as automatic start and automatic shutdown, as well as monitoring and protection devices such as oil pressure, water temperature and speed. The control panel is equipped with self start device and switching control device. The control panel is connected with the unit through cables.


The automatic diesel generator set is mainly composed of mains power monitoring, oil electromechanical monitoring, self starting controller, display alarm device, mains power switching circuit and oil electromechanical switching circuit. Relay logic control is adopted for mains power monitoring, oil electromechanical monitoring, switching circuit and self starting controller.

 Relay Control System of Diesel Generator Set

The main functions of the control system are automatic start, automatic speed increase, automatic power supply, automatic shutdown, low oil pressure alarm, high water temperature alarm, speed increase failure alarm and three start failure alarm. When the fault alarm is sent, the throttle of the diesel generator is automatically closed to realize automatic shutdown.

1) Automatic start and automatic power supply.

When the mains power is interrupted, the mains power switching circuit immediately cuts off the mains power supply circuit. At the same time, the mains power monitoring circuit makes the starting motor run through the self starting controller, so as to start the diesel generator set. After successful startup, the lubricating oil pressure rises. When the oil pressure rises to the specified value, the oil pressure sensor is started successfully, and the control circuit of the electromagnetic valve of the lubricating oil circuit is connected. The electromagnetic valve opens the oil circuit of the speed-up cylinder. The pressure lubricating oil of the diesel generator pushes the cylinder piston and drives the throttle handle to move in the speed-up direction. Under the action of the speed-up limit controller, the diesel generator operates at rated speed. At this time, under the action of the automatic voltage regulator, the generator outputs the rated voltage. Then, the diesel generator electromechanical switching circuit is connected, and the diesel generator starts to supply power to the load.

2) Automatic shutdown after mains power recovery.

After the mains power is restored, under the action of the mains power monitoring circuit, first cut off the power supply circuit of the diesel generator, then put the mains power switching circuit into operation, and the load is powered by the mains power. At the same time, the self starting controller makes the shutdown electromagnet act and controls the throttle of the diesel generator. The diesel generator runs at low speed first and then stops automatically.

3) Fault shutdown and alarm.

During the operation of the unit, when the outlet water temperature of the cooling water reaches 95 ℃± 2 ℃, the temperature controller sends an audible and visual alarm signal through the system controller and cuts off the load. At the same time, the shutdown electromagnet acts and the diesel generator unit stops running.


During the operation of the diesel generator set, when the oil pressure of the lubricating oil is lower than the specified value, the contact of the low oil pressure alarm sensor is closed, the controller sends an audible and visual alarm signal through the display alarm device, cuts off the oil electromechanical switching circuit, then stops the electromagnet operation, and the diesel generator set stops automatically. When the unit speed exceeds the rated speed, the high cycle relay in the oil electromechanical monitoring circuit acts and the diesel generator set stops automatically.


However, it should be pointed out that the automatic diesel generator set adopts relays and contactors to form the automatic control system, which requires a large number of components, complex control circuit, poor working reliability and high failure rate. So when you purchasing generator, you can choose according to your demand.


Dingbo Power is a manufacturer for diesel generator set in China, founded in 1974. All product has passed CE and ISO certification, if you are interested, welcome to contact us, we will work with you.

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