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A three-phase, 12-pole (6-pole-pair) synchronous motor is operating at an AC supply frequency of 60 Hz. The number of pole-pairs is 6, so the synchronous speed is: The number of pole-pairs is 6, so the synchronous speed is:
For example; a single-phase motor with 3 north and 3 south poles, having 6 poles per phase, is a 6-pole motor. A three-phase motor with 18 north and 18 south poles, having 6 poles per phase, is also a 6-pole motor. This industry standard method of counting poles results in the same synchronous speed for a given frequency regardless of polarity.
The rating of a brushless motor is the ratio of the motor's unloaded rotational speed (measured in RPM) to the peak (not RMS) voltage on the wires connected to the coils (the back EMF). For example, an unloaded motor of K v {\displaystyle K_{\text{v}}} = 5,700 rpm/V supplied with 11.1 V will run at a nominal speed of 63,270 rpm (= 5,700 rpm/V ...
Dahlander motor wiring for low speed (delta connection) and high speed (double star connection)The Dahlander motor is based on a 'consequent pole' connection. The primary factor in determining the speed of an induction motor is the number of poles, given by the formula
A transverse flux linear induction motor (here the primary is at top of picture) and has two sets of opposite poles side by side. (Picture from US Patent 3824414 by Eric Laithwaite ) A linear induction motor ( LIM ) is an alternating current (AC), asynchronous linear motor that works by the same general principles as other induction motors but ...
Notice the concentrated windings on the stator poles. Cross-section of switched reluctance machine with 6 stator and 4 rotor poles. Notice the concentrated windings on the stator poles. A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. The rotor does not have any windings.
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.
Extremely good speed control from standstill to full speed, and consistent torque, can be obtained by varying the generator and/or motor field current. This method of control was the de facto method from its development until it was superseded by solid state thyristor systems.