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The rotating magnetic field is the key principle in the operation of induction machines.The induction motor consists of a stator and rotor.In the stator a group of fixed windings are so arranged that a two phase current, for example, produces a magnetic field which rotates at an angular velocity determined by the frequency of the alternating current.
His motor more closely resembled modern ones in that the electromagnets surrounded a cylinder. More significantly, however, he proposed creating a true rotating magnetic field for it by supplying two sine wave alternating currents 90° apart. He gave his first public demonstration of the motor in 1888. [1]
[4] [5] A popular example of a magnet motor, although without rotating axis, was put forward by John Wilkins in 1670: A ramp with a magnet at the top, which pulled a metal ball up the ramp. Near the magnet was a small hole that was supposed to allow the ball to drop under the ramp and return to the bottom, where a flap allowed it to return to ...
The magnetic field may be produced by permanent magnets or by field coils. In the case of a machine with field coils, a current must flow in the coils to generate (excite) the field, otherwise no power is transferred to or from the rotor. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense ...
An electric motor or generator consists of a cylinderical rotating part called the rotor and a stationary part called the stator. For maximum efficiency, a gap between the rotor and stator is kept as small as possible, typically 1–2 mm. For most AC generators, the stator acts as the armature, and the rotor acts as the field magnet.
Schematic of a permanent magnet motor using brushes and magnets in the stator. A permanent magnet motor is a type of electric motor that uses permanent magnets for the field excitation and a wound armature. The permanent magnets can either be stationary or rotating; interior or exterior to the armature for a radial flux machine or layered with ...
A squirrel-cage rotor connected to the output shaft rotates within the stator at slightly less than the rotating field from the stator. Within the squirrel-cage rotor is a freely rotating permanent magnet rotor, which is locked in with rotating field from the stator. The effect of the inner rotor is to reenforce the field from the stator. [1]
Both motors and generators can be built either with a stationary armature and a rotating field or a rotating armature and a stationary field. The pole piece of a permanent magnet or electromagnet and the moving, iron part of a solenoid , especially if the latter acts as a switch or relay , may also be referred to as armatures.