- What makes the AEGIS SGR™ Bearing Protection Ring so reliable?
Answer: (1) The patented shaft grounding ring design ensures that there is a high density of discharge points provided by the Conductive MicroFiber™ all around the shaft to discharge the unwanted shaft currents to ground, (2) The AEGIS SGR™ is maintenance free and there is nothing to wear out, (3) The AEGIS SGR™ is designed to be effective when oil, grease or contamination is present on the shaft surface. When excessive particles, dirt or dust is present, an "o" ring or slinger should be installed to prevent ingress of materials.
- Why does the AEGIS SGR™ Bearing Protection Ring last so long without wearing out?
Answer: The patented technology design of the AEGIS SGR does not
use applied pressure friction for the fibers and therefore there
is no direct frictional wear applied to the fiber tips. The SGR
will literally last for the service life of the motor.
- What makes the AEGIS SGR™ Bearing Protection Ring so effective in discharging
shaft current?
Answer: Because the optimum condition to discharge unwanted high frequency VFD induced energy is created in the AEGIS SGR™ by completely surrounding the rotating shafts of the motor shaft with special conductive micro fibers. This is known as our patented technology Electron Transport Technology™ and ensures that potentially harmful shaft voltages pass safely to ground instead of through the motor bearings.
- How long will the AEGIS SGR™ Conductive MicroFiber™ shaft grounding brush last?
Answer: The AEGIS SGR™ will last for the normal service life of the motor and continue to discharge shaft voltages to ground. In lab test the shaft grounding ring showed negligible wear, less than 0.001"(0.025mm) in a 10,000 hour test at 1800 RPM.
- Is current diversion the same as shaft grounding?
Answer: Yes, current diversion is the same as shaft grounding . The AEGIS SGRTM shaft grounding ring design ensures that there is a high density of discharge points provided by the Conducive MicroFiber™ circumferencially around the shaft to discharge the unwanted shaft currents to ground. Also known as AEGISTM Bearing Protection Ring the SGR is the best solution for maintenance free sustainable motor technology to protect motor from VFD induced bearings failure.
- Why don't the fibers wear over time?
Answer: There is virtually no measurable wear because of the almost frictionless design. Even after 8700 hours of continuous operation the wear was not measurable with an optical comparator. The patented design ensures the perfect interference fit to the shaft surface.
- Is any maintenance needed for the AEGIS SGR™ once
it is installed?
Answer: AEGIS SGR™ technology is maintenance free and will not wear out. It is fully effective even when oil, grease or contamination gets on the shaft surface. Once installed per manufactures recommendation the shaft grounding ring does not require periodic maintenance or replacement for the normal service life of the motor.
- Is AEGIS SGR™ affected by oil or grease?
- Do the AEGIS SGR™ Conductive MicroFibers™ touch
the shaft?
Answer: There is an interference fit to the motor shaft
surface 360 degrees around the shaft so that the fibers are always
touching. The patented technology design ensures that the discharges
take place to protect the motor bearings.
- Will AEGIS SGR™ remain equally effective during its long service life?
Answer: AEGIS SGR™ is designed not to wear out during the
service life of the motor. This is because of the ultra-low friction
of the fiber interference with the shaft.
- Will the AEGIS SGR™ cause wear to the shaft of
the motor?
Answer: The motor shaft will not wear because there is virtually no friction in the patented technology design and therefore there is no measurable wear of the shaft, even after over 25,000 hours of continuous operation.
- Why do conventional shaft grounding brushes wear
out?
Answer: Whether metal bristle or carbon block, conventional
shaft grounding brushes use a spring loaded mechanism to apply pressure
onto the shaft while it is rotating. This causes rapid wear of the
brush surface and frequent replacement.
- Why do conventional shaft grounding brushes need
maintenance?
Answer: Conventional metal or carbon brushes need frequent
maintenance both to ensure they are free from oil or contaminants
and to replace due to normal wear. Also the springs will weaken
over time and require replacement.
- Should conventional carbon block copper shaft grounding brushes
be replaced by AEGIS SGR™ on VFD motors?
Answer: Yes. AEGIS SGR™ replaces conventional shaft grounding brushes, improves reliability, and decrease maintenance costs. Conventional shaft grounding brushes need frequent maintenance and become less effective over time. They rely on the spring tension to press the brush against the rotating shaft. This causes the brush, material to wear as it rubs on the shaft - sometimes in as little as 3 months. In addition, oil, grease, dirt or oxidation will break the conductive path and reduce or will reduce or prevent conventional brushes from discharging shaft currents.
- Where do the VFD induced shaft voltages go with no AEGIS SGR™ brush installed?
Answer: The shaft voltages will build up on the motor shaft and discharge through the bearings. This happens because the voltages induced onto the motor shaft overcomes the dielectric of the grease film between the bearing's ball and race.
- Why are these shaft currents so destructive?
Answer: Because they occur literally hundreds of thousands of times per minute while the motor is running. Over time the bearing race becomes heavily frosted and mat start to flute in a very short period of time…sometimes causing failure in only a few months.
- What does bearing frosting look like?
Answer: Frosting will look like a gray or white line along
the bearing race where the discharges take place:
Image 1: Bearing frosting line
- What does bearing fluting look like?
Answer: Fluting will look like a washboard pattern of Gary
or white along the bearing race where the discharges take place:
Image 2: Bearing Fluting, the distinctive "washboard" pattern
- What happens to the motor as frosting and fluting
take place in the bearings?
Answer: Vibration and bearing noise will continue to increase
as the problem gets worse. This noise, caused by the bearing ball
coming in contact with the fluting or severe frosting of the bearing
race is an indicator of potential catastrophic failure. Installing
the AEGIS SGR™ will divert the currents which cause the bearing
failures away from the bearings and will discharge the currents
to ground.
- Will electrical bearing damage always occur in
a VFD application?
Answer: Yes - with no alternate path to discharge shaft current,
pitting of the motor bearing will take place during VFD operation.
These discharges will continue and will always seek the path of
least resistance - usually through the motor bearings. Installing
AEGIS SGR™ will create an alternate path for these discharges and
divert current away from the motor bearings.
- How about VFD duty motors, are they safe from
bearing damage?
Answer: Electrical bearing discharges will occur even in
VFD duty motors and must be addressed to avoid potential failures.
Without a device like AEGIS SGR™ installed, the VFD induced shaft
currents still discharge through the motor bearings and may eventually
cause failure.
- How about IEEE 841 motors, are they safe from
electrical bearing damage?
Answer: No. All motors, including the NEMA 841 and premium efficiency motors will experience electrical bearing damage when operated by VFDs - unless they are protected from shaft current. AEGIS SGR™ NEMA kit installes to the motor end bell to clear the rotating portion of the bearing isolator.
- We just installed VFDs on many of our motors and
so far everything is OK, should I be worried about shaft current?
Answer: Yes - even if you have not experienced excess noise,
vibration or bearing failure so far, the VFD induced shaft currents
continuously discharge through the motor bearings during operation
and may cause an unplanned failure unless you have a means to discharge
them. By installing the AEGIS SGR™ Conductive MicroFiber™ shaft
grounding brush, you will provide the best means of protection and
prevention to avoid potential failure.
- From a preventative maintenance perspective what
would you recommend?
Answer: In order to prevent potential catastrophic failures,
AEGIS SGR™ Conductive MicroFiber™ brush.
- Can I operate the AEGIS SGR™ over the shaft keyway?
Answer:The AEGIS SGR™ should not operate over the shaft keyway. SGR microfibers should not come in contact with the keyway during operation. Upon installation, you may slide the SGR over the keyway but the final installation should not be over the keyway.
- What is the wear rate of the micro fibers?
Answer: The unique Conductive MicroFibers™ used in the AEGIS
SGR™ are a very tough material and will not readily wear. Because
of the patented technology design, there is virtually no friction to
cause fiber wear like with conventional brush configurations.
- What is the best way to measure shaft voltage?
Answer: The best measurements are taken with an oscilloscope
by placing the probe in the middle of the end of the shaft - drive
end or non-drive end and observing the shaft voltages.
- Can an RMS measurement be used to test for the
presence of shaft voltages?
Answer: Measuring RMS is not the best way to check for damaging
voltages on the shaft but will indicate the presence of the shaft
voltage. RMS "averages" the voltage reading and therefore does not
show the voltage spikes that cause the electrical bearing discharges.
- Will the AEGIS SGR™ work in washdown duty motor?
Answer: Yes, the AEGIS SGR™ works well in wash down duty motors because the fibers are not affected by water.
- Should one or two AEGIS™ SGRs be installed on
the motor?
Answer: For smaller frame motors with shaft diameters of
less than 2" you will generally only need a single AEGIS SGR™ on
the motor. This is because circulating currents are not present
in these smaller motors. Any motor with larger than 2" shaft should
have an SGR on both the drive end and non-drive end of the motor
to discharge both VFD currents and circulating currents.
- If AEGIS SGR™ is installed outdoors, will water
affect performance?
Answer: There is no problem with water or moisture - AEGIS
SGR will continue to perform even If some water gets inside AEGIS
SGR™.
- Does any corrosion occur to AEGIS SGR™ with water?
Answer: Fresh water will not cause corrosion.
- Is it possible to press the SGR into the motor housing instead of using the mounting brackets?
Answer: Yes, you can press fit the SGR into the motor housing instead of using the mounting brackets. The SGR has an OD tolerance of 0.02" (0.5mm) so you'll want to measure the SGR before boring out the motor end bell. We recommend a 0.003" to 0.004" crush fit between the bore and the SGR OD. This should be a clean dry press. No oil or other lubricants are to be used for press assist.
- Where does the "category" of "medium" voltage motors begin? What input voltage?
Answer: Medium voltage is anything 2140v+. The currents induced by these drives are generally higher than with low voltage motors. Keep in mind that the line voltage will not be present on the shaft and the induced voltages will be much smaller than the line voltage. The induced voltages would be below 1000v pk, and probably less than 200v pk. However, since currents are higher, we recommend the iPRO.
