From the largest (1000+ MW) nuclear powered generators, to gas turbines, to smaller (1 MW) industrial generators, Sohre TurbomachineryⓇ has a shaft riding brush that can be used to protect your machine from stray shaft currents and measure shaft voltage patterns to diagnose generator problems.
Installed on thousands of machines throughout the world
U.S.A., China, Canada, Saudi Arabia, India, Pakistan, Chile, Israel, France, Spain, Germany, U.K., Italy, Greece, U.A.E., Brasil, Argentina, Japan, Korea, Indonesia, Malaysia, Singapore, and many more.
Grounding stray currents
Stray currents in turbo generators lead to damaging electrical discharges
- Erosion of bearings, gearboxes, and seals
- Erroneous signals from vibrations and temperature probes
- In extreme (and rare) cases they can lead to self excitation and catastrophic failures
Grounding shaft currents eliminates electrical discharges, but it is not as simple as it may sound. An effective grounding brush needs to be able to ground low voltage and withstand high voltage.
- Low voltage can be damaging. As little as 0.5 Volts of potential difference can lead to damage to parts such as gearboxes. Grounding such low potentials require very low resistance and consistent contact with the rotating shaft.
- High voltage is not rare. Condensing turbines and gas turbines can generate voltage spikes in excess of 1000 Volts.
Sohre Shaft riding brushes can maintain consistent, low resistance contact with the machine shaft which allows for grounding of low voltage discharges, yet they are the electrical insulation and ruggedness to dissipate high voltage discharges.
Monitoring the condition of the generator
A variety of generator fault conditions can be detected as patterns on generator shaft voltage using an oscilloscope (or a monitoring device) attached to a Sohre brush.
- Bearing insulation failure/degradation, can be seen as a drop in shaft voltage near the bearing, or as a voltage wave synchronous with the shaft rotation.
- Single rotor ground faults can be seen as a DC offset on the generator shaft.
- Problems with the excitation system filters lead to rapid voltage spikes with a fixed time interval between spikes