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Damage to Rotor Parts Caused by Generator Shaft Current

Aug. 16, 2021

The rotating shaft of the generator set must use a certain lubrication method to keep the rotor and the bearing in direct contact, that is, the entire rotor is insulated with an oil film from the stator when it rotates at high speed. Because the rotor has resistance to the ground, once it is charged, a voltage to the ground will be established. When the voltage rises to a certain value, it will break down in the area with the smallest resistance and spark discharge will occur. The main consequences of this discharge are as follows:

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1. Melting metal particles in the discharge area, forming extremely tiny galvanic pits on the metal surface.

2. The accumulation of pits makes the surface rough and loses its luster. If it occurs on the bearing bush, pure mechanical wear will occur.

3. The molten metal particles enter the lubrication system, causing the lubricant to be contaminated, and the lubricating performance of the entire lubricating system deteriorates, and the lubricant containing a large amount of metal particles will reduce the oil film resistance and accelerate the progress of spark erosion.

4. Local high temperature occurs in the bearing area of the bearing, which destroys the oil film, burns the metal, increases abrasion, and finally causes serious friction damage.

In the rotor system of rotating machinery, the most prone to spark discharge is the bearing surface of radial bearing and thrust bearing, the working tooth surface of gear coupling and the sealing surface of floating ring. Changes in various conditions (such as load, temperature, lubrication conditions, and rotor vibration, etc.) may reduce the resistance of the oil film and the air gap, causing electric spark discharge in these parts. For radial sliding bearings, the development of bearing galvanic pits will cause severe corrosion on the surface of the babbitt alloy, which will not only change the original clearance of the bearing, but also cause abrasion and scratches on the bearing surface due to the decrease in surface finish. Localized heat and burns.

The abrasion of babbitt on the surface of the high-speed light-load bearing of the generator set will cause a part of the bearing pads to lose the preload effect on the rotor journal, and the rotor will easily induce oil film vortex when rotating, which will cause the instability of the rotor system. The unstable oil film in turn will cause a sharp drop in the resistance of the oil film of the bearing, causing more shaft currents to pass through the area, aggravating the effect of electric sparks, mutually energizing each other, and ultimately causing damage to the bearing or rotor system.

Jiangsu Starlight Power Generation Equipment Co., Ltd. was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. The company has a registered capital of 218.88 million yuan. The company covers an area of 86,000 square meters and a building area of 55,000 square meters. There are more than 660 employees, including 456 professional technicians and 106 senior technicians. It has 46 sales and service outlets nationwide. The main products are diesel engines, generator sets, and diesel generators, providing users with a one-stop service of design, supply, debugging and maintenance at any time. Starlight has always insisted on using first-class talents, building first-class enterprises, manufacturing first-class products, creating first-class services, and making every effort to build a first-class domestic enterprise. If any question please feel free to visit our website https://www.dieselgeneratortech.com/ or send email to sales@dieselgeneratortech.com.

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