Synchronous means: to occur at regular or fixed intervals. An AC Synchronous Motor is an electrical motor that rotates at a fixed speed, regardless of any increase or decrease in load. The motor will keep its fixes speed regardless of the torque required up until it reaches its stall torque rating.  If the load becomes greater than the motor's stall torque, the AC Synchronous Motor will not slow down until it reaches a point at which it will stall and stop turning.  The AC Synchronous motor is an effective way to obtain a fixed speed at a very low motor system cost.  No expensive driver or amplifier is necessary.  Most synchronous motors are used where precise timing and constant speed are required.

AC Synchronous Motors range in size from sub-fractional horsepower to over 10,000 horsepower. Smaller synchronous motors (pictured here) can be found in household devices such as clocks, timers, fans and cassette players, and as stepper motors in computer disk drives and printers. Larger synchronous motors are used in process industries and drive equipment such as compressors. Large synchronous motors most commonly employ a three-phase system. The smaller AC Synchronous Motors commonly use a single-phase system. The single-phase AC Synchronous Motor is the focus of this site.