Understanding Induction Motor Nameplate Information

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  • Topic: Electric motor, Horsepower, Synchronous motor
  • Pages : 7 (2553 words )
  • Download(s) : 86
  • Published : November 23, 2010
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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 interchangeable The U.S. motor industry has worked on a standardized basis for more than three-quarters of a century. The standardization agency — National Electrical Manufacturers Association (NEMA) — was established in 1926 “… to promote the standardization of electrical apparatus and supplies.” As a result of this group's efforts, you can expect “standard” motors from different manufacturers to meet or exceed minimum performance parameters and, for the most part, be about the same size. A critical part of making motors interchangeable is ensuring that nameplate information is common among manufacturers. The common language of the motor nameplate enables installation and maintenance personnel to quickly understand and recognize exactly what type of motor they're dealing with during a new installation or replacement procedure. The NEC states that the motor nameplate must show the following information: * Rated voltage or voltages

* Rated full-load amps for each voltage level
* Frequency
* Phase
* Rated full-load speed
* Insulation class and rated ambient temperature
* Rated horsepower
* Time rating
* Locked-rotor code letter
* Manufacturer's name and address
In addition to this required information, motor nameplates may also include data like frame size, NEMA design letter, service factor, full-load efficiency, and power factor. Finally, some nameplates may even include data like bearing identification numbers, certification code, manufacturer serial number, and symbols and logos. Basic nameplate data. In order to fully understand the details presented on motor nameplates we'll examine each of these items more closely and explain its importance. Rated voltage — Motors are designed to yield optimal performance when operating at a specific voltage level, or a combination of voltage levels in the case of dual-voltage or tri-voltage motors. This value is known as the nameplate voltage. In recognition of the fact that voltage changes on your power distribution system occur due to changing load conditions within your facility and on the utility supply that feeds your facility, motors are designed with a 10% tolerance for voltage above and below the rated nameplate value. Thus, a motor with a rated nameplate voltage of 460V should be expected to operate successfully between 414V and 506V. Rated full-load amperage — As the torque load on a motor increases, the amperage required to power the motor also increases. When the full-load torque and horsepower is reached, the corresponding amperage is known as the full-load amperage (FLA). This value is determined by laboratory tests; the value is usually rounded up slightly and recorded as the nameplate value. Rounding up allows for manufacturing variations that can occur and some normal voltage variations that might increase the full-load amps of the motor. The nameplate FLA is used to select the correct wire size, motor starter, and overload protection devices necessary to serve and protect the motor. Frequency — To operate successfully, the motor frequency must match the power system (supply) frequency. In North America, this frequency is 60 Hz (cycles). In other parts of the world, the frequency may be 50 or 60 Hz....
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