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Single-phase induction motors are used extensively for smaller loads, such as garbage disposals and stationary power tools. Although traditionally used for constant-speed service, single- and three-phase induction motors are increasingly being installed in variable-speed applications using variable-frequency drives (VFD).
The AC electric motor used in a VFD system is usually a three-phase induction motor. Some types of single-phase motors or synchronous motors can be advantageous in some situations, but generally three-phase induction motors are preferred as the most economical. Motors that are designed for fixed-speed operation are often used.
An induction generator produces electrical power when its rotor is turned faster than the synchronous speed. For a four-pole motor (two pairs of poles on stator) powered by a 60 Hz source, the synchronous speed is 1800 rotations per minute (rpm) and 1500 RPM powered at 50 Hz. The motor always turns slightly slower than the synchronous speed.
The three-phase induction is now used for the vast majority of commercial applications. [51] [52] Mikhail Dolivo-Dobrovolsky claimed that Tesla's motor was not practical because of two-phase pulsations, which prompted him to persist in his three-phase work. [53] The General Electric Company began developing three-phase induction motors in 1891 ...
The shaded-pole motor is the original type of AC single-phase motor, dating back to at least as early as 1890. [1] A shaded-pole motor is a motor, in which the auxiliary winding is composed of a copper ring or bar surrounding a portion of each pole to produce a weakly rotating magnetic field. [2] When single phase AC supply is applied to the ...
A power inverter, inverter, or invertor is a power electronic device or circuitry that changes direct current (DC) to alternating current (AC). [1] The resulting AC frequency obtained depends on the particular device employed. Inverters do the opposite of rectifiers which were originally large electromechanical devices converting AC to DC.
Vector control (motor) Vector control, also called field-oriented control (FOC), is a variable-frequency drive (VFD) control method in which the stator currents of a three-phase AC or brushless DC electric motor are identified as two orthogonal components that can be visualized with a vector. One component defines the magnetic flux of the motor ...
A linear induction motor's primary typically consists of a flat magnetic core (generally laminated) with transverse slots that are often straight cut [6] with coils laid into the slots, with each phase giving an alternating polarity so that the different phases physically overlap. The secondary is frequently a sheet of aluminium, often with an ...