The common classification of motors is AC and DC motors. DC motors can be divided into brush DC motors and brushless DC motors. DC motor has good starting characteristics and speed adjusting characteristics. However, with carbon brushes, the armature will wear out which shorten the lifecycle and need replacement. Although brushless DC motors have less maintenance problems, they usually cost more and have limited applications.
AC motors can be divided into synchronous motors and asynchronous motors. Synchronous motors can have smaller size to achieve the same output compare to the asynchronous motor. However, permanent magnet is rare on earths which make the cost rise significantly. Although asynchronous motors may have larger weight and volume under the same power and torque, it is cost effective and easy to maintain compare to other motors.
Asynchronous motors, also known as induction motors, can be subdivided into single-phase and three-phase motors. Because of their high reliability, they are the most widely used motors in various industries and daily life applications.