The operation of a simple motor basically consists of a coil, whose main function is to rotate between two permanent magnets. The magnetic poles of the coil, represented as magnets, are attracted by the opposing poles of the fixed magnets. The coil rotates so you can carry these magnetic poles as close as possible to each other. However, upon reaching this position, the current direction is automatically reversed and the opposing poles eventually repel each other, giving continuity to the rotor drive.
In a simple motor, in which the stator is composed of permanent magnets, and the rotor is a coil of enameled copper wire, through which the electric current passes, once the electric currents produce magnetic fields, this coil will behave like a Permanent magnet.
As the opposing poles become attracted, the coil is exposed to a torque that acts to rotate the coil, undergoing an angular acceleration and continuing its rotation. This torque continues until the coil poles can reach the opposing poles of the fixed magnets. In this case, there is no torque, since the lever arms are zero.
Electric motors of alternating current, with the exception of motors of the universal type, are machines of constant speed. However, it is possible to have the stator coils of an induction motor re-connected in such a way that it is possible to double the number of poles and thus reducing the speed by half.
The present stators can be composed of two independent windings, calculated for the specific number of poles that are expected, by means of reversible poles, to vary the poles, and with a small number of connections, the synchronous motor speed can be varied.
Each of these windings can be connected in a way that allows two different speeds, two-for-one ratio, thus obtaining up to four synchronous speeds independently, therefore, will never be able to provide speeds at the intermediate level.
With winding rotor induction motors ECP4107T-4 it is possible to obtain any speed from zero to approximately the synchronism speed, by varying a simple resistance attached to the winding of the rotor, and which does not imply heating of the rotor, since losses Resistance are external to the motor.