Shaft Grounding: Research
Industry-Leading Shaft Grounding Research and Expert Guidance
Helwig Carbon’s BPK Shaft Grounding is a culmination of world-class engineering expertise, industry-leading spring force research, and expert understanding of carbon graphite to provide the industry’s best shaft grounding solution.
Learn about our groundbreaking research and utilize our resources to ensure shaft grounding selection and installation to protect your motor bearings from damage caused by electrical discharge from VFDs
More Effective Than a Shaft Grounding Ring
Bearing Protection Kits™ mitigate shaft voltage and other electrical noise. In a controlled testing environment using our Patented BPK-Probe™, the following oscilloscope screenshots reveal a significant reduction in induced shaft voltage with our BPK-SB compared to a carbon fiber grounding ring or an unprotected motor shaft. The lower voltage values achieved by the BPK-SB is a result of our advanced silver graphite grounding brush technology. Silver graphite is more than 5X lower in resistance than carbon-fiber, which significantly reduces the risk of induced shaft currents flowing through the bearings, making silver graphite more effective for protection. The test was conducted on a 10HP Nidec motor with the following specifications: 460VAC, 1765 RPM, and driven by an Emerson VFD at 52Hz
BPK Selection Guide
The Helwig Carbon shaft grounding device – Bearing Protection Kits™ (BPK) – fit a variety of motor shafts, offer several mounting options, and are easy to install and maintain. Helwig Carbon bearing protectors will deliver many years of superior performance in motor shaft grounding and will typically last 10 years or more! Our BPK selection Guide will help you determine which kit offers the best shaft grounding solution for your application.
For selection of models not shown, click here. For shaft diameters >6 in (152mm) or for high vibration/extremely rough applications, contact us for assistance: 414-354-2411.
Explore BPK Applications
Saving Compressor Motor Bearings
University Uses BPK to Prevent Motor Failure
Shaft Grounding for Submersible Pump Manufacturing
Preventing Damage on Rooftop Fan Motor
Shaft Grounding Contamination Test
Explore BPK Product Literature
BPK Brochure
BPK v. Carbon Fiber Ring
BPK Pocket Guide
BPK-Probe Brochure
Shaft Grounding Whitepaper
Additional Education, Installation, and Troubleshooting FAQ
Installation Guides & STP files
MultiFit Bracket Installation Options
Shaft Grounding FAQ
What Causes Bearing Damage?
Bearing Damage caused by VFDs and PWMs occurs because these drives induce electrical discharge onto the motor shaft. The discharge seeks the path of least resistance to ground, which is usually through the motor bearings. This causes arcing, pitting, fluting, and burnt grease, leading to bearing failure and costly repairs.
There are other causes of bearing damage which must be dealt with separately: https://www.helwigcarbon.com/what-causes-bearing-failure/
What are the Signs of Bearing Damage
How Can I Detect Damaging Voltage?
How Does BPK Shaft Grounding Work?
Does the BPK Require Ongoing Maintenance?
How Long Do BPKs Protect Motor Bearings?
Do You Have a Specification Guide?
BPK Probe FAQ:
What is the BPK Probe?
The BPK-Probe Shaft Voltage Detection Device is an easy-to use tool that measures common mode voltage on a motor shaft and the risk to the motor bearings from this voltage. Common mode voltage is a byproduct of Variable Frequency Drives (VFDs) and Pulse Width Modulation (PWM) drives. When common mode voltage discharges through the motor bearings, it can cause arcing, fluting, pitting, burnt grease, and eventual failure.
With the BPK-Probe™ grounded, typically to the motor frame, the Probe tip is placed against the rotating motor shaft and the test is performed. The BPK-Probe displays easy pass/fail results along with the measured voltage level in seconds. In addition, the BPK-Probe also has an embedded grounding device to show the effectiveness of Helwig’s Bearing Protection Kit™ (BPK).
Test results are recorded on a micro-SD card and can also be recorded on the included tablet oscilloscope or other third-party devices. With the BPK-Probe DataLink App, test results can also be stored and viewed online.
What is the BPK Probe? What Motors and Devices Should Be Tested?
Motors driven from a Pulse Width Modulation (PWM) source or Variable Frequency Drives (VFD) are common sources of unwanted shaft voltage due to the common mode voltage they create. Typically whenever a speed control is used there is risk of voltage building on the motor shaft, causing bearing discharges.
Additionally, driven devices like drive shafts, drums, propeller shafts, gearboxes, etc., are all susceptible to damaging discharges due to common mode or static voltage discharge and should be monitored.