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the article citations: time:2016-06-09 10:19:40
what can be done to reduce the likelihood of premature bearing failure?
corrective measures fall into two main categories,and they each present advantages and disadvantages. some common ones are as follows:
corrective measures fall into two main categories,and they each present advantages and disadvantages. some common ones are as follows:
electrical:
drive output filtering: most commonly used are referred to as dv/dt filters, dv/dt representing the rate of rise of the voltage pulse with respect to time. this is basically an inductive impedance introduced to slow the rate of rise of the voltage pulse. by reducing voltage stresses imposed on the motor, effective dv/dt filters have been shown to reduce common mode currents by up to 30%. and common mode currents are one of the primary causes of bearing damage.
pros:
reduces the magnitude of voltage spikes at the motor terminals, so it also helps to maintain winding and motor insulation integrity.
in most applications, can be safely used where motors leads are 150 meters or more in length
reduces the harmonic content of the drive output
cons:
more costly than many mechanical methods (see below)
requires additional space near the drive for mounting (typically installed external and adjacent to the drive)
mechanical:
s: a non-conductive material is used to isolate the bearings. due to expense and to the relatively lower probability of bearing problems on small motors, insulated bearings are normally used on iec frame 315/nema frame 500 or larger motors. insulated non-drive end (nde) bearings are often standard, with insulated drive end (de) bearings typically optional.
pros:
provides incremental protection at a modest price
requires no additional floor space to install
cons:
subject to wear/contamination over time, resulting in insulation failure
“transfers” the stray currents to other connected components, for example direct-coupled loads, which may then have to be protected in some fashion
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