We recently came across a white paper by MachineDesign titled “How to Eliminate Early Bearing Failure Due to Electrical Arcing.” This topic is of special interest to us at CBR Bearing because we know the damage that can be caused to traditional steel bearings when they are subjected to electrical arcing.
In the paper, the author states, “In variable frequency drives, stray shaft currents…occur as a result of the high-frequency switching operation of the IGBT (insulated gate bipolar transistor). This circuitry, used to control the speed of the motor, creates parasitic capacitances in the motor’s major components, including the rotor and stator. Because the bearing acts as the bridge between these components, it is exposed to these differences in electrical potential.”
As you can imagine (or probably have experienced if you are familiar with equipment that has VFDs), electrical arcing can cause substantial damage to bearings when the voltage exceeds what the bearing’s lubrication can handle. In extreme situations, small pieces of the steel balls in the bearings can actually break off and contaminate the grease, causing the bearing to fail.
The white paper goes on to state that the best way to prevent stray currents from affecting your equipment’s bearings is to use bearings with non-conducting rolling elements, such as silicon nitride balls. This virtually eliminates the possibility of electrical arcing, according to the paper, and “…provide[s] a more effective barrier than a mere coating…” The author goes on to say, “Compared to coated bearings, hybrid bearings provide the best protection possible, because the electrical resistance of the ceramic material allows the bearings or rolling elements to be literally impervious to damage caused by electrical arcing.”
As you know if you’ve looked around our website at all, at CBR Bearing, we sell ceramic hybrid bearings that use aerospace-grade silicon nitride balls. If you want high-quality, durable bearings, we’ve got you covered!
We sometimes get asked if there are any downsides to going with ceramic hybrid bearings instead of steel bearings. The white paper answers this question perfectly: “Ceramic is a more expensive material than steel, so the upfront cost for a hybrid-ceramic bearing is higher than for its steel counterpart. However, since hybrid-ceramic bearings protect against electrical erosion/arcing, the life of the bearing is significantly extended. This results in longer maintenance intervals and, ultimately, lower TCO, thereby making hybrid-ceramic bearings an excellent return on your investment.”
Yes, ceramic hybrid bearings are typically more expensive than steel bearings, but at CBR, we have some of the most affordable ceramic hybrid bearings on the market. If you want to keep costs down even further, you also have the option of converting your existing steel bearings to ceramic hybrid bearings. Contact us to learn more about this service or to place an order on new ceramic hybrid bearings. We have many sizes in stock, ready to ship out today!
You can read the full white paper by MachineDesign by clicking here. It is free to download, but they do require that you give them some personal information in order to access it.