Working Principle of Diesel Generator Set

When the diesel generator set is used as the standby power supply, once the external power supply is interrupted, the generator set should be started to supply power to the low-voltage bus of the substation to ensure the continuity of power supply. Generally, there are manual starting mode and automatic starting mode for starting diesel generator. Generally, manual starting is adopted for manned substation. For unattended substations, automatic starting is adopted. However, the automatic starting device is often accompanied by manual starting function to facilitate use.

According to the starting power source, the starting of diesel engine can be divided into electric starting and pneumatic starting. The electric starting uses the DC motor (generally series excited DC motor) as the power to drive the crankshaft to rotate through the transmission mechanism. When the ignition speed is reached, the fuel will start to burn and work, and the starting motor will automatically exit the work. The motor power supply adopts battery, and its voltage is 24V or 12V. Pneumatic start is to make the compressed air stored in the gas cylinder enter the diesel engine cylinder, use its pressure to push the piston and make the crankshaft rotate. When the ignition speed is reached, the fuel will start to burn and work, and stop supplying air at the same time. When the start is successful, the diesel engine will slowly enter the normal operation state.

Therefore, the execution object of the diesel engine automatic starting device is not the contactor of the motor or the starting solenoid valve of the starting circuit. The automatic starting device should have three links: receiving the starting command, executing the starting command and cutting off the starting command. Some devices can be started repeatedly, usually three times. If the three starts are unsuccessful, an alarm signal will be given. For large capacity units, there is also a warm-up operation procedure, which can prevent the rough start of the diesel engine from causing the thermal stress overload of the cylinder and affecting the service life of the diesel engine.

Connection mode between engine and generator

1. Flexible connection (connect the two parts with a coupling).

2. Rigid connection. There are high-strength bolts to connect the rigid connecting piece of the generator with the flywheel plate of the engine. After that, it is placed on the common underframe, and then equipped with various protective sensors (oil probe, water temperature probe, oil pressure probe, etc.) to display the working status of various sensors by the control system. The control system is connected to the generator and sensors through cables to display data.

Working principle of generator set

The diesel engine drives the generator to operate and convert the energy of diesel into electric energy. In the diesel engine cylinder, the clean air filtered by the air filter is fully mixed with the high-pressure atomized diesel injected by the fuel injection nozzle. Under the upward extrusion of the piston, the volume is reduced and the temperature rises rapidly to reach the ignition point of diesel.

When diesel oil is ignited, the mixed gas burns violently, and the volume expands rapidly, pushing the piston down, which is called work. Each cylinder works sequentially in a certain order, and the thrust acting on the piston becomes the force to push the crankshaft through the connecting rod, so as to drive the crankshaft to rotate.

When the brushless synchronous alternator is installed coaxially with the crankshaft of the diesel engine, the rotation of the diesel engine can be used to drive the rotor of the generator. Using the principle of electromagnetic induction, the generator will output induced electromotive force and generate current through the closed load circuit.

Only the fairly basic working principle of power generating set is described here. In order to obtain usable and stable power output, a series of diesel engine and generator control, protection devices and circuits are also needed.

If the continuous operation lasts for more than 12h, the output power will be about 90% lower than the rated power. The diesel engine of the diesel generator is generally a single cylinder or multi cylinder four stroke diesel engine. Next, I will only talk about the basic working principle of the single cylinder four stroke diesel engine: the starting of the diesel engine is to rotate the diesel engine crankshaft by manpower or other power to make the piston reciprocating up and down in the top closed cylinder.

Dingbo Power is manufacturer of diesel generators in China, if you are interested in diesel generator, please contact us by email dingbo@dieselgeneratortech.com, we will work with you.