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Electric Motor

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http://www.reliableplant.com/Read/25199/methods-optimize-electric-motor http://www.wisegeek.com/what-are-the-different-types-of-electric-motors.htm http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p009.shtml http://www.engrcs.com/club/SHEP/Motor_Overview.pdf for acceleration time n power rating http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemot.html http://www.oddparts.com/acsi/motortut.htm http://www.freescale.com/webapp/sps/site/overview.jsp?code=DRMTRELECTMTR Understanding Induction Motor Nameplate Information May 1, 2004 12:00 PM, By Ed Cowern, P.E., Baldor Electric Co. 12 Comments | Related Content Share135 Keeping the language common among manufacturers is critical to making motors …show more content…

Specialized motors can be designed for “short-time” requirements where intermittent duty is all that's needed. These motors can carry a short-time rating from 5 minutes to 60 minutes. The NEMA definition for short-time motors is as follows: “All short-time ratings are based upon corresponding short-time load tests, which shall commence only when the windings and other parts of the motor are within 5°C of the ambient temperature at the time of the test.” By using short-time ratings, it's possible to reduce the size, weight, and cost of the motor required for certain applications. For example, you may choose to install an induction motor with a 15-minute rating to power a pre-operation oil pump used to pre-lube a gas turbine unit because it would be unusual for this type of motor to be operated for more than 15 minutes at a time. Locked-rotor code letter — When AC motors are started with full voltage applied, they create an inrush current that's usually many times greater than the value of the full-load current. The value of this high current can be important on some installations because it can cause a voltage dip that might affect other equipment. There are two ways to find the value of this current: * Look it up in the motor performance data sheets as provided by the manufacturer. It will be noted as the locked-rotor current. * Use the locked-rotor code letter that defines an inrush current a motor requires when starting it.

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