There are several commonly used con

There are several commonly used control DC motors: First, the original DC speed regulation system uses DC constant voltage to supply power to the armature of the DC motor, and realizes speed regulation by changing the resistance in the armature circuit. The method has simple operation, convenient manufacture and low cost. But the disadvantages are low efficiency, softer mechanical characteristics, and cannot be smoothed in a wide speed range, so it is rarely used. Second, in the late 1930s, generator motors (also known as rotary converter groups) appeared. Using magnetic amplifiers, motor extenders, thyratrons and other control devices, excellent speed regulation performance can be obtained, such as wide speed regulation range (10:1 ~ 10:1), small variable speed, stable speed regulation, etc. Especially when the motor decelerates, it can be controlled by the generator, and it is easy to feed back the inertia of the flywheel on the motor shaft to the grid. This way, on the one hand, stable braking characteristics can be obtained, and on the other hand, energy loss can be reduced and efficiency can be improved. However, the main disadvantage of the generator and motor speed control system is the need to add two rotating motors and some auxiliary excitation equipment equivalent to the speed control motor, so it is large in scale and difficult to maintain. Third, since the emergence of the mercury arc converter, the mercury arc converter has been used to replace the above-mentioned generator and motor system, which further improves the speed regulation performance index. In particular, the rapid response of the system is unmatched by generator and motor systems. However, mercury arc converters still have some shortcomings: maintenance is inconvenient, especially mercury vapor will cause certain harm to maintenance personnel. Since the mid to late 1980s, thyristor rectifiers have replaced the original DC generators, electric generators and mercury rectifiers, making a great leap in DC drive technology. At the same time, the control circuit has also achieved high integration, miniaturization, high reliability and low cost. With the application of the above-mentioned technologies, the performance indicators of the DC speed control system have been greatly improved, the application range has been continuously expanded, and the DC speed control technology has also been continuously developed.