Motors of the four-pole design have proven to be quite reliable. The two-pole design, as used in most of the centrifugal compressor drives, does not enjoy the same reputation. Sleeve bearings are the bearings of choice for compressor drives. Ring oil lubrication is most common on these motors, but a degree of reliability can be added by using pressurized oil from the compressor lubrication system.

One area of concern that applies to induction motors is the potential of a high torque if the motor is re-energized at the wrong time after a trip. The torque capability of the motor is 500 to 700% of normal when reconnected at the wrong part of the coast down cycle. The level of torque potential is of a magnitude that a failure of the couplings, shafts, and/or gears will occur. It is not practical on motor-compressor systems to design for such high stresses. The safest procedure is to let the drive train coast to a stop before re-energizing. Alternately, though somewhat costly, is to use electric relaying that can detect the point where re-energizing is safe and automatically reclose the breaker at the proper time.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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