Featured Shaft Grounding Articles
 Device protects motor bearings against electrical damage and lubricant problems
The US sealing specialist Garlock has collaborated with Electro Static Technology (EST), inventor of the patented Aegis bearing protection ring, to produce a device that protects motor bearings from electrical damage as well as from lubricant loss and contamination.
The maintenance-free SGi shaft earthing bearing isolator (above) combines Garlock's Guardian non-sparking bronze labyrinth seal with an Aegis shaft earthing ring. It is aimed at motors controlled by variable speed drives (VSDs) in applications such as pumps, fans and high-speed spindles.
Shaft grounding: Keep motors alive on variable-frequency drives
Posted on PlantServices.com: Already common in HVAC, pumping and industrial automation systems, the use of variable-frequency drives (VFDs) is growing. VFDs are smaller and more powerful, more reliable, easier to program and less expensive than ever. But, VFD/motor systems must be designed for reliability and trouble-free operation to keep the energy savings, which can reach 20% or more, from being wiped out by a system failure. VFDs can induce electric currents on motor shafts that ruin bearings, shorten motor life and diminish system reliability. One way to mitigate the effects of these currents is to ground the motor shaft to protect bearings and eliminate expensive repairs.
Grounding rings on plant motors mitigate potentially damaging shaft voltages
 In this edition of PlantServices.coms Always Up and Running What Works section, shaft grounding rings are discussed to enhance the reliability of electric motors at a Monarch Cement Plant in Kansas. The AEGIS iPRO rings were recommended and installed by Independent Electric Machinery (IEMCO), a large motor service and repair facility to improve the reliability of a 5,000 HP pulverizer motor.
Grounding-Ring Technology for Variable Frequency Drives (PDF file)
Variable-frequency drives (VFD's) provide substantial energy savings and control for commercial and industrial process applications. Unfortunately, previously unanticipated bearing failures are occurring because modern VFD's induce harmful voltage on the motor shaft. As the resulting current travels through motor bearings it can cause catastrophic failure and costly downtime.
Extending Motor Life With Sustainable Shaft Grounding
May 6, 2010 2:21 PM, By ADAM WILLWERTH Electro Static Technology Mechanic Falls, Maine
Realizing the full energy-saving potential of variable-frequency drives
With the rising cost of energy, the use of variable-frequency drives (VFDs), also known as inverters, is growing. By optimizing electrical flow to an alternating-current (AC) motor, a VFD can provide substantial energy savings. Within the field of flow control, the potential for increased efficiency with VFDs is especially dramatic. Many centrifugal fans and pumps run continuously, often at reduced loads. Because the energy consumption of such devices correlates to their flow rates cubed, the motors driving them will use less power if controlled by a VFD. In fact, if a fan's speed is reduced by half, the horsepower needed to run the fan drops by a factor of eight. In constant-torque applications (reciprocating compressors, conveyors, mixers, etc.), in which more-accurate process control is the main objective, a VFD can be programmed to prevent a motor from exceeding a specific torque limit.
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 motors 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.
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 Technologys 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.
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 |
