Factors that Influence Shaft Grounding Performance
Recognizing the need for shaft grounding for your electric motor is the first step towards solving a shaft voltage issue. Even if a protection kit is installed, it does not guarantee that your motor is protected. Many factors can influence the effectiveness of a shaft grounding solution.
Examples of what to watch for when selecting or installing a shaft grounding solution include:
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Ensure that the selected kit has proper conductivity, as seen with silver graphite or carbon fiber strands. Inadequate construction that allows low or diminishing contact force over time will leave bearings vulnerable to electrical damage.
Contamination is also a major issue. Most shaft grounding designs will work when installed but will fail when exposed to debris, rust, or grease. Over greasing is by far the most common form of contamination and will cause bristles or carbon fibers to be ineffective.
Avoid kits that require regular maintenance. The need to regularly lubricate or apply epoxy to the shaft or decouple the motor could result in time-consuming maintenance routines and an increased risk of incorrect installation.
A less obvious contributor to poor shaft grounding performance is an inadequate grounding scheme. Even if the protection kit is installed correctly the motor may not be appropriately grounded for high-frequency discharges. Many times paint can add resistance that affects the ground path. Sometimes this is also referred to as an earthing issue. This is very important for initial and continued performance when protecting motor shafts.
To measure, record, and document the effectiveness of your kits we recommend Helwig’s patented BPK-Probe. This easy-to-use instrument requires no technical training or use of complicated support equipment like an oscilloscope. With an easy-to-read, on-board diagnostic screen for real-time test results and BLE connection to the free Data-Link app, technicians can easily test and record bearing protection performance along with application information, historical data, etc.
Couple the BPK-Probe with Helwig’s Bearing Protection Kit (BPK) with its industry-leading performance, effectiveness in contaminated environments, ability to handle high-frequency discharges, and very long maintenance free life and you can be assured your motors are being protected. Please contact Helwig Carbon or visit our website www.helwigcarbon.com for more information on our complete grounding solution.
Brian Stone
Product Manager
Bearing Protection
