Why Does 800kva Electric Generator Have Unstable Idle Speed

The unstable idle speed of 800kVA diesel generator refers to that it runs fast and slow at idle speed, but the regularity is not strong. And it is easy to shut down during rapid deceleration, shift or load. This phenomenon is mostly caused by the failure of the governor. The main causes are as follows.

(1) Flying ball wear.

At idle speed, the opening of the flying ball is the smallest, and the spring sliding sleeve. Due to the wear of the small roller of the flying ball, it extends too far to the flying ball, resulting in irregular direct collision with the flying ball body, resulting in unstable idle speed. At this time, touch the refueling lever with your hand, and you will feel slightly impacted. 

(2) Poor elasticity or improper adjustment of idle spring.

When the diesel generator is running, the increase of load will reduce the speed. If the idle spring or starting spring becomes soft, the oil supply toothed rod cannot move rapidly to the oil increasing direction to improve the speed, which will cause the automatic flameout of the diesel generator in serious cases.

(3) Improper adjustment of speed stabilizing spring.

During idle operation, the control force of speed regulation is also small due to the small centrifugal force of flying ball. If 800kva diesel generators decelerate suddenly, the adjustment movement of the oil supply rod may exceed the idle position and shut down the diesel generator. In order to prevent this situation, the speed stabilizing spring behind the governor cover facing the oil supply gear rod to the idle position; If the spring is too soft or biased after adjustment, it will weaken or fail to stabilize the speed, making the idle operation unstable.

(4) Poor oil supply of low-pressure oil circuit or containing water and air.

This will make the fuel supply increase and decrease, especially in the low-speed area, which will lead to the unstable operation of the diesel generator.

(5) Excessive wear of camshaft cone bearing of fuel injection pump support cam.

In this case, the camshaft will move irregularly in the axial direction, resulting in unstable speed of diesel generator.

(6) Uneven fuel supply of fuel injection pump, improper fuel supply or poor fuel injection.

Under the condition of low-speed operation, if the oil supply is uneven or incorrect, it will have a great impact on the stability of speed, but this instability shows that the pin is regular and the periodicity is short.

(7) Insufficient cylinder compression.

When the cylinder compression force decreases, because the degree of decline of each cylinder is not necessarily the same, even if the fuel supply of the fuel injection pump is balanced, the combustion situation may still be different, resulting in unstable speed at low speed.