Electric motors and electrical concepts (Electric machine and electric machine theory concept) Motor definition: refers to an electromagnetic device that realizes the conversion or transmission of electric energy according to the law of electromagnetic induction. Electric motors are also called motors (commonly known as motors) and are represented by the letter "M" in the circuit (the old standard uses "D"). Its main function is to generate driving torque as a power source for electrical appliances or various machinery. Type of motor 1. According to the working power supply According to the different working power of the motor, it can be divided into DC motor and AC motor. Among them, AC motors are also divided into single-phase motors and three-phase motors. 2. According to the structure and working principle, the motor can be divided into DC motor, asynchronous motor and synchronous motor according to the different structure and working principle. Synchronous motors can also be divided into permanent magnet synchronous motors, reluctance synchronous motors and hysteresis synchronous motors. Asynchronous motors can be divided into induction motors and AC commutator motors. Induction motors are divided into three-phase asynchronous motors, single-phase asynchronous motors and shaded-pole asynchronous motors. AC commutator motors are divided into single-phase series motors, AC and DC dual-purpose motors and repulsion motors. According to the structure and working principle, DC motors can be divided into brushless DC motors and brushed DC motors. Brushed DC motors can be divided into permanent magnet DC motors and electromagnetic DC motors. Electromagnetic DC motors are divided into series-excited DC motors, shunt-excited DC motors, separately-excited DC motors and compound-excited DC motors. Permanent magnet DC motors are divided into rare earth permanent magnet DC motors, ferrite permanent magnet DC motors and Alnico permanent magnet DC motors. 3. Classification according to starting and operating modes According to the different starting and operating modes of motors, they can be divided into capacitor-start single-phase asynchronous motors, capacitor-run single-phase asynchronous motors, capacitor-start-run single-phase asynchronous motors and split-phase single-phase asynchronous motors . 4. Classified by use It can be divided into drive motors and control motors. Driving motors are divided into electric tools (including drilling, polishing, polishing, slotting, cutting, reaming, etc.) motors, household appliances (including washing machines, electric fans, refrigerators, air conditioners, tape recorders, video recorders, and DVDs). Motors for machines, vacuum cleaners, cameras, hair dryers, electric shavers, etc.) and other general small machinery equipment (including various small machine tools, small machinery, medical equipment, electronic instruments, etc.). Control motors are divided into stepping motors and servo motors. 5. Classification according to the structure of the rotor According to the structure of the rotor, the motor can be divided into a cage induction motor (the old standard is called a squirrel cage asynchronous motor) and a wound rotor induction motor (the old standard is called a wound induction motor). 6. Classification by operating speed According to the different operating speeds of motors, they can be divided into high-speed motors, low-speed motors, constant-speed motors, and speed-regulating motors. Low-speed motors are divided into gear reduction motors, electromagnetic reduction motors, torque motors and claw-pole synchronous motors. In addition to stepped constant speed motors, stepless constant speed motors, stepped variable speed motors and stepless variable speed motors, speed regulating motors can also be divided into electromagnetic speed regulating motors, DC speed regulating motors, PWM variable frequency speed regulating motors and Switched reluctance speed motor. The rotor speed of an asynchronous motor is always slightly lower than the synchronous speed of the rotating magnetic field. The rotor speed of the synchronous motor has nothing to do with the size of the load and always maintains the synchronous speed.