Grounding Rings vs. MH&W's CoolBLUE® Product
Variable frequency drive (VFD) inverters are often at fault when bearings within a motor fail prematurely as part of inverter-drive systems. These VFD inverters generate high-frequency electric current that passes to a motor's shaft and on to its bearings. Prolonged exposure to excess current will negatively impact the motor's bearings and result in motor standstill, an extremely costly problem to fix.
Grounding rings are a common but flawed solution to the premature failure of bearings, diverting rather than absorbing current to create a protective ground connection. Alternately, CoolBLUE® cores from MH&W International Corp. address grounding ring failings and offer critical bearing protection from damaging excess current along the motor shaft.
What Do Grounding Rings Do?
VFDs utilizing alternating current (AC) motors generate an electrical current at their insulated gate bipolar transistors (IGBTs) that then travels along a motor's shaft. As it does so, the current seeks the path of least resistance, typically leading it to the motor bearings. After surpassing a bearing's lubricant resistance, discharging currents to a motor's housing create tiny fusion craters on a bearing's surface that intensify in quantity and size with repeated use. Continuing to erode over time, bearings will develop fluting, pitting, frosting, and related issues, which will cause them to eventually fail.
Grounding rings, however, provide an alternative, lower-resistance route for the current to travel. Instead of coming into contact with the motor bearings, the current passes from the shaft to the grounding ring mounted on it, and then proceeds to ground, which is typically the motor housing. This safeguards the bearings against the high-frequency current.
Grounding rings have numerous applications, such as VFD AC and direct current (DC) motors, power and wind generators, and testing devices. Per drive and motor manufacturing companies, a braided strap connecting the motor to ground is ideal for this high-frequency path.
Problems With Grounding Rings
While grounding rings can protect bearings from electrical current damage, they're not an optimal choice because they simply redirect excess electrical current rather than absorb it. As a result, your motor and generator systems can still fail, leading to unnecessary maintenance and downtime as well as the accompanying labor costs and productivity losses this entails.
Advantages of Nanotech's CoolBLUE® Cores
Introduced in 2009 to the United States market, MH&W's innovative CoolBLUE® cores are designed to solve both the problems that grounding rings are meant to remedy, as well as the ways in which the rings fall short. Instead of sending current elsewhere in the motor to be grounded, these nanocrystalline inductive absorbers are common mode chokes surrounding power conductors between the VFD and motor. They prevent shaft damage by choking VFD's high-frequency common mode currents that originate at their IGBTs. By absorbing excess current to eliminate it at the source, our cores prevent damaging levels from reaching the motor shaft, thereby protecting the motor bearings.
Additional benefits of CoolBLUE® cores include:
- Easy, permanent solutions. We've designed our CoolBLUE® cores to be installed once and stay within the system without requiring future replacements. After a simple 10-minute installation, they will continue to perform effectively for the full life cycle of the system.
- Enhanced system lifespan. Using CoolBLUE® cores effectively protects motor bearings, lengthening the service life of your system while negating the need for maintenance, replacement parts, and system downtime. This is partially because, unlike grounding rings, our cores are non-mechanical in nature.
- Reduced costs. Given the dependability of our cores, you save on the fees and productivity losses associated with breakdowns. Also, CoolBLUE® cores are typically equal to or less than the price of hybrid grounding ring/bearings, standard grounding rings, and brushes.
- Additional protection. CoolBLUE® cores outperform grounding rings and brushes by also alleviating other electrical issues such as circulating currents and stray grounding currents for enhanced protection and effectiveness.
- Increased impedance. Our cores reduce high frequency in addition to excess current. In doing so, they increase system impedance.
Since 1964, the team at MH&W has specialized in power conversion and filter solutions, offering high-performance magnetic components like chokes and our CoolBLUE® cores. These cores offer a cost-effective, permanent method for addressing shaft current and successfully preventing bearing damage and related electrical current concerns in motors and generators. Contact us today to learn more about our innovative CoolBLUE® cores, or request a quote to begin your project.