供应2018年新品电容450V 350V 250V厂家螺栓400V8200UF

DC electric drive and AC motor drive have been born in the 19th century. They have a history of more than 100 years and have become the main driving device of power machinery. Because of the technical problems at that time, in a very long period of time, the DC motor is basically used in the drive system which needs to be controlled by speed regulation. The disadvantages of DC motor are as follows: 1. Because DC motor has commutative spark, it is difficult to be used in the bad environment of flammable and explosive gas; 2. It is necessary to change the brush and commutator regularly. The maintenance is difficult and the life is short. 3. The structure is complex and it is difficult to produce large capacity, high speed and high voltage DC motor.