Motors can be simply divided into DC motors and AC motors, and AC is further divided into synchronous motors and asynchronous motors.

　　1. DC motor

　　The advantage of a DC motor is that it can easily adjust the speed by changing the voltage and can provide a larger torque. It is suitable for loads that require frequent adjustment of the speed, such as the mine hoists.

　　Now AC motors can also adjust the speed by changing the frequency, but the price is more expensive than ordinary motors.

　　The disadvantages of DC motors are their complex structure and high failure rate. Compared with AC motors, DC motors have complicated windings (excitation windings, commutating pole windings, compensation windings, armature windings), but also add slip rings, brushes and commutators. This not only places high requirements on the manufacturer's process, but also the later maintenance costs are relatively high.

　　Therefore, DC motors are in an embarrassing situation of declining in industrial applications.

　　2. Asynchronous motor

　　The advantages of asynchronous motors are simple structure, stable performance, convenient maintenance, low price and simple manufacturing process. Therefore, it has been the most widely used in industry.

　　Asynchronous motors are divided into squirrel-cage motors and wire-wound motors. The difference lies in the rotor. Squirrel-cage motors have high reliability, but the disadvantages are that the torque is small, the starting current is large, and the load that requires a large starting torque is difficult to handle. The winding motor has higher torque and is suitable for loads such as rolling mills and hoists. However, it adds slip rings, water resistors and other accessories, and the price is relatively high.

　　If the asynchronous motor is to be used for high-power loads, it needs to be equipped with a reactive power compensation device.

　　3. Synchronous motor

　　In addition to the advantages of synchronous motors that can compensate reactive power in over-excitation state, they also have the advantages of precise speed control, high stability, strong overload capacity, and high operating efficiency.

　　Synchronous motors cannot be started directly, and asynchronous start or frequency conversion start is required for cooperation. Therefore, one of the disadvantages of synchronous motors is the need to add additional equipment for starting.

　　Synchronous motors run by excitation current, so the second disadvantage of synchronous motors is that they need to add excitation devices, which are mostly supplied by silicon controlled rectifiers.

　　In summary, the principle of selecting a motor is that the motor performance meets the requirements of the production machinery, and the motor with simple structure, low price, reliable operation and convenient maintenance is preferred. In this respect, AC motors are superior to DC motors, AC asynchronous motors are superior to AC synchronous motors, and squirrel cage asynchronous motors are superior to winding asynchronous motors.

　　For production machinery with stable load and no special requirements for starting and braking, ordinary squirrel-cage asynchronous motors should be preferred, which are widely used in machinery, water pumps, fans, etc.

　　Starting and braking are more frequent, and production machinery that requires larger starting and braking torques, such as bridge cranes, mine hoists, air compressors, and irreversible rolling mills, should use wound asynchronous motors.

　　Where there is no requirement for speed regulation, a constant speed or improvement of power factor is required, synchronous motors should be used, such as medium and large-capacity water pumps, air compressors, hoists, mills, etc.

　　The speed regulation range is required to be above 1:3, and the production machinery that needs continuous, stable and smooth speed regulation should adopt a separately excited DC motor or a squirrel cage asynchronous motor or synchronous motor with frequency conversion speed regulation, such as large precision machine tools, planers, rolling mills, hoists, etc.

　　The production machinery that requires large starting torque and soft mechanical characteristics uses series-excited or compound-excited DC motors, such as trams, electric locomotives, and heavy-duty cranes.

　　Lithium-ion battery (LIB) has become the main energy storage solution in modern social life. Among them, lithium iron phosphate batteries are a perfect replacement for lead-acid batteries, and they are the first choice for grid-connected peak shaving, off-grid energy storage, photovoltaic energy storage, UPS, data center and other industries.

　　The motor system is matched with a high-rate performance lithium battery system, which is a very promising way to use it.