photo © 2007 Peter Van den Bossche | more info (via: Wylio)
Synchronous motors are characterized by their rotor with attached field winding, slip rings and a stator carrying an armature winding. The armature winding is able to develop a magnetic field inside the motor as it is excited by the rotation of the rotor and its field winding. Synchronous motors are available with sub-fractional, fractional, and high-horsepower ranges. Most fractional horsepower synchronous motors are used in applications where precise, constant speed is required. Synchronous motors are provided with a starting winding, consisting of copper alloy bars located in the pole face, parallel to the shaft, and brazed at the ends to copper alloy rings.
Synchronous motors are available in subfractional self-excited sizes to high-horsepower direct-current excited industrial sizes. In the fractional horsepower range, most synchronous motors are used where precise constant speed is required. Synchronous motors are usually single-speed devices, with the rotation speed governed by the fixed power line frequency. In our case, instead of rotating our magnet within a rotating magnetic field in just a couple of coils, we are going to accelerate it past a large number of coils one-by-one. Synchronous motors work as the application of three-phase AC power to the stator causes a rotating magnetic field, which is then set up around the rotor. The rotors of the synchronous motors are then energized with DC.
A more detailed article provides a closer look at these motors:
AC Synchronous motors have two major types. The first is known as “non excited” and the second as “direct current excited”. Motors that are non-excited are manufactured in two designs, which are reluctance and hysteresis. Both of these designs will have self starting circuits and require no external excitation. The reluctance motor is a kind of synchronous motor that creates non-permanent magnetic poles on a rotor that is ferromagnetic.
L&S Electric both repairs and sells synchronous motors. For more information, please contact us.