Featured Shaft Grounding Articles
 Making Motors Sustainable at Time & Life Building
A preventative maintenance plan that reduces the life-cycle cost of operations in a prominent building at the heart of New York City serves as a good example of how the push for more sustainable, green, building management has led to a growing awareness of a chronic, widespread problem with HVAC motors - electrical bearing damage.
Harvard University, University Operations Services offers Motor Shaft Grounding Services
FMO now offers Motor Shaft Grounding, a maintenance program that prevents bearing
failure and significantly extends motor life. All Variable Frequency Drives (VFD) controlling
AC motors develop Induced Shaft Currents that discharge through the bearings (illustration #1).
During this process, arcing between the ball bearings and the outer wall of the bearings causes fluting
(illustration #2) which will eventually lead to bearing failure. Typically, motor manufacturers estimate that a motor
will last between 30,000 - 40,000 operating hours. However, fluting can reduce this life expectancy by up to 50%.
The Blackstone Case Study, outlined below, illustrates how our simple 4-step process can eliminate harmful currents
and significantly reduce repair and replacement costs.
Sustainable Shaft Grounding Ensures Reliability of Energy-Saving VFDs in Data Center HVAC Systems
According to this white paper written by Adam Willwerth, development manager, Electro Static Technology the use of variable frequency drives (VFDs), also known as inverters, can reduce the cost of cooling data center computer servers. By optimizing the power usage of HVAC fans or pumps, VFDs can provide substantial energy savings. But if the increased efficiency is not sustainable, those savings vanish. Currents induced by VFDs on motor shafts can wreak havoc with motor bearings, dramatically shortening motor life and causing costly repairs and/or downtime. To mitigate these currents and realize the full potential of VFDs, effective, reliable shaft grounding is essential.
Marathon Electric Introduces New Shaft Grounding Ring Technology for Inverter Driven Motors
Marathon Electric, innovators of energy efficient motor technology for the long run, has introduced the latest innovation in inverter-driven motor technology with a field installable Shaft Grounding Ring (SGR) accessory for industrial, commercial and HVAC/R motors. This option is especially suited for Marathon’s Blue Max®, Black Max®, Micro Max® and NEMA Premium XRI® models.
Baldor Electric Company Offers AEGIS Bearing Protection Ring
Baldor Electric Company, Fort Smith, Arkansas based manufacturer of energy saving industrial electric motors, mechanical power transmission products, drives and generators, announces the availability of a bearing protection ring as an option on Baldor™ Reliance motors.
Grounding Motor Shafts to Suit VF Drives
With the rising cost of energy, more variable-frequency drives (VFDs) are being installed for motion and speed control. They are highly efficient, but the currents they induce on motor shafts can wreak havoc with bearings, which dramatically shorten motor life and reduce system reliability. To mitigate these currents and realize the full potential of VFDs, a cost-effective method of shaft grounding is essential.
Fulfilling the promise of variable frequency drives
With the rising cost of energy, the use of variable frequency drives (VFDs) is growing at an increasing rate. By optimizing the frequency of a three-phase alternating-current (AC) induction motor’s voltage supply, a VFD controls the motor’s speed and torque while providing energy savings. And, these energy savings can be quite substantial—20 percent or more—making VFDs a “green” solution as well as a wise money-saving investment.
Shaft Grounding-A Solution To Motor Bearing Currents
Variable Frequency Drives induce shaft voltages onto the shaft of the driven motor because of the extremely high speed switching of the insulated gate bipolar transistors which produce the pulse width modulation used to control AC motors in heating, ventilation, air conditioning and refrigeration systems. This voltage induced on the shaft becomes great enough to overcome the dielectric of the oil film in the bearing
causing bearing discharges known as electrical discharge machining effect. Unless mitigation for these shaft voltages is employed in the motor, the motor’s bearings may become damaged from the electrical bearing currents which cause pitting and excessive bearing noise, fluting and finally motor failure. The cause of this problem and commonly applied mitigation methods are discussed as well as a new and highly effective
conductive micro fiber shaft grounding ring technology which resolves these problems.
AEGIS WTG Saves Oregon Wind Turbine Bearings
Case study describing solution to wind generator bearing failure from high-frequency currents induced on the shafts of wind turbine generators through parasitic capacitive coupling. Voltages can reach levels of 60 amps and 1,200 volts or greater. If not diverted, these currents discharge through the generator’s bearings, causing pitting and fluting that result in premature bearing failure and catastrophic turbine failure.
Third Time's a Charm, Today's Energy Solutions (Fall 2008)
Encouraging results from recent uptower testing at a wind farm in Oregon indicate that our conductive-microfiber bearing protection ring is effectively preventing generator bearing damage. Specially designed by our engineering team to protect wind turbine motor bearings, the ring appears to have solved a chronic bearing failure problem once and for all.
Design Aspects of Conductive Microfiber Rings for Shaft Grounding Purposes
by H. William Oh and Annette Muetze
IEEE Paper - Winner of the 2007 First Prize Paper Award at the IEEE Conference.
Engineered Systems White Paper Download
Electro Static Technology’s White Paper focuses on mitigating the variable frequency drive- (VFD-) induced shaft currents that can be extremely damaging to motor bearings, and a new technology that employs a circumferential ring of conductive micro fibers to discharge harmful currents and provide a low-cost solution to the problem.
Dealing with Shaft and Bearing Currents Presented by Tom Bishop, Technical Support Specialist, Electrical Apparatus Service Association.
This comprehensive paper addresses key issues relates to shaft and bearing currents in electric motors and generators... Topics include recognizing symptoms, methods of testing, and various solutions to mitigating bearing and shaft currents and new technology introductions such as the AEGIS Shaft Grounding Ring. The complete 53 page "Select Presentations" CD-ROM includes the 14 page paper as well as copies of the 39 slides. Order through EASA (PDF file).
Application of Static Charge Dissipation to Mitigate Electric Discharge Bearing Currents by H. William Oh
IEEE Paper-Application of Static Charge Dissipation to Mitigate Electric Discharge Bearing Currents, May 2007,. Presented by Dr. Annette Muetze and H. William Oh, M.E. This paper focuses on a new mitigation technique where any voltage build-up across the bearing is discharged via static charge dissipation through the AEGIS Shaft Grounding Ring.
Purdue Nanotechnology Labs Employ AEGIS Bearing Protection Ring for shaft grounding to ensure a constant flow of clean air.
New Shaft Grounding Brush Extends Life of AC and DC Motors
By John R. Hall
Of The NEWS Staff
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