What kind of bearings are used in electric motors?
The most common rolling bearing types in electric machinery are deep groove ball bearings, cylindrical roller bearings, and angular contact ball bearings due to their versatility and overall performance.
What is motor bearing current?
Bearing currents occur when there is an induced voltage on the motor shaft that is high enough to over- come the breakdown voltage on the bearing lubricant. Cause current to flow directly from the shaft, through a bearing, then through the motor or load frame and then into ground as shown in Fig.
How is motor bearing insulation resistance measured?
The insulation on both sides of the metal plate can be checked separately by connecting the ohmmeter between terminals A and G, and between A and B. The thrust-bearing insulation resistance should measure from about 10,000 ohms to infinity.
What is NDE bearing?
In the basic bearing system, the floating bearing is situated at the non-drive end (NDE) and the located bearing is situated at the drive end (DE). On request, the located bearing can also be supplied at the non- drive end (NDE). For ordering all standard and non-standard motors quote.
Why bearings are used in motors?
The purpose of a bearing in an electric motor is to support and locate the rotor, to keep the air gap small and consistent and transfer the loads from the shaft to the motor. The bearings should be able to operate at low and high speeds whilst minimizing frictional loses.
Why bearing is heated?
The force needed to mount a bearing increases rapidly with bearing size. Because of the mounting force required, larger bearings cannot easily be pressed onto a shaft or into the housing. Therefore the bearing or the housing is heated before mounting.
What is an insulated bearing?
Insulated bearings prevent premature bearing failures eventually caused by stray electrical currents. Insulation properties must remain stable regardless of environmental conditions, in particular when bearings are stored, handled and operated in humid climates.
What is motor shaft voltage?
Shaft voltage occurs in electric motors and generators due to leakage, induction, or capacitive coupling with the windings of the motor. It can occur in motors powered by variable-frequency drives, as often used in heating, ventilation, air conditioning and refrigeration systems.
How do you test an insulated bearing?