Although the structure of DC motor three-phase AC asynchronous motor is complex, maintenance inconvenience, but due to its good speed performance and the starting torque is big, therefore, the production of machinery requiring high speed machine or bigger starting torque often adopts the direct current motor drives.
Advantages of DC motor:
(1) good speed regulation performance, wide range of speed regulation, easy adjustment.
(2) the starting and braking torque is large, easy to start and stop quickly.
(3) easy control.
(1) large scale equipment such as rolling mill, electric locomotive, large and medium sized Longmen planer, mine shaft hoist and lifting equipment.
(2) the place where a battery is used as a source of power, such as automobiles, tractors, etc..
Compared with the asynchronous motor, although the structure is complex, the price is high, the maintenance is not convenient, but in the speed regulation performance by its unique merit.
1 speed uniform smooth, stepless speed regulation (Note: asynchronous machine to change the speed of the pole of the method is called speed control).
2 speed range, speed ratio of up to more than 200 (speed ratio is equal to the maximum speed and minimum speed ratio), so the mechanical transmission gear box can be greatly simplified.