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Padmapriya.mantha · 03-08-2017, 06:32 AM

Theory for brake test on a 3 phase induction motor
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jaseela123d · 07-08-2017, 10:24 AM

An induction motor, 3-phase induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor necessary to produce the torque is obtained by electromagnetic induction of the magnetic field of the stator winding. Therefore, an induction motor can be made without electrical connections to the rotor. The rotor of an induction motor can be the type of wound or squirrel cage.

Three-phase induction motors with squirrel cage are widely used in industrial drives because they are robust, reliable and economical. Single-phase induction motors are widely used for smaller loads, such as appliances such as fans. Although traditionally used in fixed speed service, induction motors are increasingly used with variable frequency drives (VFD) in variable speed service. VFDs offer particularly important energy saving opportunities for existing and potential induction motors in centrifugal fan, pump and variable torque compressor load applications. Squirrel cage induction motors are widely used in fixed speed and variable frequency (VFD) applications.

History

In 1824, the French physicist François Arago formulated the existence of rotating magnetic fields, called rotations of Arago. By manually activating and deactivating the switches, Walter Baily demonstrated this in 1879, effectively the first primitive induction motor.

The first induction motors without alternating current were invented independently by Galileo Ferraris and Nikola Tesla, an engine model that has been demonstrated by the first in 1885 and by the latter in 1887. Tesla applied for US patents in October and November 1887 And was awarded some of these patents in May 1888. In April 1888, the Royal Academy of Science of Turin published the research of Ferraris on its polyphase AC motor which details the foundations of motor operation. In May 1888, Tesla presented the technical document A New System for AC Motors and Transformers to the American Institute of Electrical Engineers (AIEE) describing three types of four-stator-pole motor: one with a four-pole rotor forming A non-starter reluctance motor, another with a winding rotor forming an automatic start induction motor and the third a true synchronous motor with DC supply separately energized to the rotor winding.

George Westinghouse, who was developing an AC power system at the time, licensed the Tesla patents in 1888 and purchased a US patent option. In the concept of Ferraris induction motor. Tesla was also employed for a year as a consultant. Westinghouse employee C. F. Scott was assigned to assist Tesla and later took over the development of the induction motor at Westinghouse. Mikhail Dolivo-Dobrovolsky invented the cage rotor induction motor in 1889 and the three-member transformer in 1890. He further asserted that the Tesla motor was not practical because of the two-phase pulsations, which led him to persist in his three-phase work . Although Westinghouse achieved its first practical induction motor in 1892 and developed a line of 60 hertz polyphasic induction motors in 1893, these early Westinghouse motors were biphasic motors with coiled rotors until B. G. Lamme developed a rotating rotor.

The General Electric Company (GE) began developing three-phase induction motors in 1891. In 1896, General Electric and Westinghouse signed a cross-licensing agreement for the design of a rod winding rotor, later called a squirrel cage rotor. Arthur E. Kennelly was the first to bring up the full meaning of complex numbers (using j to represent the square root of minus one) to designate the 90 ° rotation operator in the CA problem analysis. GE Proteus Steinmetz developed greatly the application of complex amounts of AC, including an analysis model now commonly known as the equivalent Steinmetz induction circuit. The induction engine improvements flowing from these inventions and innovations were such that a 100 horsepower induction motor currently has the same mounting dimensions as a 7.5 horsepower engine in 1897.

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