DC motors are widely used. The motor most widely used is the DC electric tools. DC electric tool is a handled or removable mechanized tools use small-capacity DC motors or solenoids through drive mechanism drive working head. The world's first DC electric tools are drill manufactured in 1894. In 1900, people created a three-phase power frequency electric drill, driven by three-phase asynchronous motors. In 1913, people produced the first AC and DC electric drill driven by single-phase series motor. After the 1980s, with the development of economy in the world, power tools technology has been developed rapidly. Into the new century, there are nearly thousands of power tools in the world, the annual output is more than 100 million units. Power tools are light, easy to carry. Compared with hand tools, power tools can improve labor productivity several times, and have higher efficiency than the efficiency of conventional pneumatic tools, low cost (Needless compressor), vibration and noise is small, easy to automatically control. Therefore, power tools, gradually replace the hand tools, have been widely used in machinery, construction, electrical and mechanical, metallurgical equipment installation, construction of bridges, various aspects of residential renovation, agricultural production, health care, and health. And widely used by self-employed workers and their families, is a widely used large surface mechanized tools, its development prospects are very broad.
In power plants, the exciter and battery charger of synchronous generator are DC generator; boiler feed powder machine prime mover is a DC motor. In addition, in many industrial sectors, such as large-scale steel rolling equipment, large precision machine tools, mine hoist, streetcars, cable equipment demanding a consistent line speed, usually it adapts DC motor as the prime mover to drive the working machine. DC generator is usually used as a DC power supply, output power to a load; DC motor is used as a prime mover to drive a variety of production mechanical, output mechanical energy to the load. In the control system, the DC motor as well as have other uses, such as speed motor, servo motor. Although the DC motor and DC generator have various purposes, but they are basically the same structure, both use electric and magnetic interactions to achieve conversion of mechanical energy and electrical energy.
The greatest weakness of the DC motor is commutation, that consume more non-ferrous metals, high cost, maintenance and overhaul operation are also a problem. Therefore, the motor manufacturing industry is working to improve speed performance of AC motor, and a lot AC motor replace DC motor. However, in recent years, in the use of silicon controlled rectifier replacing DC generator, we have made great progress. All rotary motors including DC motors, in fact, their manufacturing are based on the two basic principles what we know. One is: wire cutting flux generating induced electromotive force; the other one is: the electromagnetic force effect on the carrier conductor in a magnetic field. Therefore, from the structure, any motor includes a magnetic portion and a circuit portion. Seen from the above principle, any motor embodies electrical and magnetic interactions, it is the unity of two opposites of electricity, magnetism.