Dc motor drive mode. Dc drive as a relatively cheap drive way has long been widely used in electric equipment. Dc system itself has some inherent defects in performance, maintenance and so on. Electric vehicles before the 1990s were almost entirely driven by dc motors. Dc motor itself has low efficiency, large volume and mass, commutator and carbon brush limit the improvement of its speed, high speed of 6000 ~ 8000r/min.
An electric motor is made of the phenomenon of a energized coil rotating by force in a magnetic field. Compared with the DC motor, the AC motor of forklift has incomparable excellent performance. The following forklift manufacturers explain the characteristics of AC motor and DC motor. An AC motor consists mainly of an electromagnet winding or distributed stator winding for generating a magnetic field and a rotating armature or rotor. No dust generated after carbon brush wear, clean internal environment, improve the service life of the motor. Ac motor work efficiency is higher, and there is no smoke, smell, do not pollute the environment, noise is smaller. Because of a series of advantages, it is widely used in industrial and agricultural production, transportation, national defense, commercial and household appliances, medical electrical equipment and other aspects.
Induction motor AC drive system is a new technology developed in 1990′s. The outstanding advantage of ac motors is that they do not have carbon brushes, nor do they have the high current limitations that dc motors usually have, which means that in practice they can get more power and more braking torque, so they can run faster. The heat of the AC motor mainly occurs in the stator coil of the motor shell, which is convenient for cooling and cooling. Therefore, ac motors require significantly fewer components than DC motors, no wear parts that need to be replaced regularly, almost no maintenance, more efficient, more durable.
Dc motor is a motor that converts direct current energy into mechanical energy. Because of its good speed regulating performance, it is widely used in electric driving. Dc motor according to the excitation mode is divided into permanent magnet, other excited and self-excited three categories. Carbon brush wear produces dust, which directly affects the service life of the motor. The motor is not fully enclosed structure, the heat generated in the motor during work, the heat dissipation effect is weak, is not conducive to the motor for a long time. Energy backflush efficiency on braking is less than 15%. Dc motor has complex structure and high manufacturing cost; Maintenance trouble, and dc power supply, high maintenance costs. Generally used for starting under heavy load or requiring uniform adjustment of speed machinery, such as large reversible rolling mill, winch, electric locomotive, trolley, etc., are driven by dc motor.
In recent years, with the progress of ac induction motor variable frequency technology, and high power semiconductor devices and microprocessor speed, improved ac induction motor drive system compared with dc motor drive system, with high efficiency, small volume, low quality, simple structure, maintenance free, easy to cooling and the advantages of long service life. The speed range of the system is wide, and it can realize low speed constant torque and high speed constant power operation, which can well meet the speed characteristics required by the actual driving of electric vehicles. It can be said that it is the rapid advance of semiconductor technology that gives birth to the technological revolution of AC motor and greatly enhances the control ability of AC motor. Moreover, with the continuous decline in the price of electronic components, the cost of ac motor controller hardware can be reduced, thus laying a foundation for the large-scale promotion and application of AC drive system, creating conditions.
Post time: Oct-04-2021