It has become a consensus to choose electric forklifts in many work scenarios with higher environmental requirements. Electric forklift is the use of battery to provide power to the forklift, by the motor will be converted into mechanical energy. First, electric forklift generally has three motors, namely walking motor, lifting motor and steering motor. The driving system of the walking motor finally provides the driving torque to the wheel. The lifting motor directly drives the lifting system hydraulic pump,It drives the lifting hydraulic system, while the steering motor is used to drive the steering pump in the electric forklift with full hydraulic steering. With the improvement of hydraulic system, the lifting motor and steering motor are often combined in high-configuration electric forklifts.
The so-called DC forklift, refers to the lifting and walking are using DC motor, then AC forklift use AC motors for lifting and walking.
To sort out the difference, we figure out the structure and working mode of AC motor (three-phase AC induction motor) and DC motor. The principles of DC motor and AC motor are different, and their structures are also different. At the same power, the DC motor's external size is larger than the AC motor, because the DC motor needs more space to install the commutator and carbon brush. In a DC motor, permanent magnets are installed in the excitation coils of the stator, and the armature windings are installed on the rotor. As the rotor rotates, DC current always flows through the carbon brush, which keeps close contact with the commutator, causing friction. When the battery power is insufficient or the current of the forklift climbing motor is increased, the heat of the commutator will increase, causing the wear and failure of the brush.
The characteristics of the DC motor are determined by the output voltage of the controller, so when the battery is low, the output characteristics of the motor will change. Dc motor controller is a high-power high-frequency switching device (such as MOSFET) composed of H-bridge circuit, using PWM pulse-width modulation technology, by changing the duty ratio of the chopper control algorithm, to adjust the speed and acceleration of dc motor. Speed range has a certain range. Because of the mature control technology of DC motor, there are many Oems also keen to use DC electric control.
Therefore, the biggest difference between AC system and DC system is as follows:
1. Dc motor needs to be installed with steering gear and carbon brush. Due to the influence of size, the freedom of vehicle design is inferior to that of AC motor;
2. The carbon brush of dc motor is a wearing part, which needs to be maintained, resulting in time cost and economic cost;
3. Dc system is greatly affected by battery power and climbing strength, and current increase will bring corresponding changes to performance. Under the same battery capacity, ac system will use longer time;
4. DC motor moving parts more, mechanical friction produces a lot of heat, the heat generated by the armature winding on the rotor can not be directly emitted into the air in time, bring about the change of overload capacity;
5. AC motor speed range is wider than the dc motor with the same power, better adaptability;
6. The AC system can achieve energy regeneration more effectively. The inertial energy generated by the forklift is recharged into the battery, which prolongs the single shift service time and service life of the battery.
7. The control algorithm of DC motor is mature and simple, and the price of DC electric control will be reduced accordingly.
In a word, AC drive system will be more and more widely used as the upgrading technology of forklift truck. This is called "the revolutionary technology of electric forklift in the 21st century", which will have a certain impact on the technology level, product sales, market share, profits and even the image of innovation of forklift enterprises. After all, the competition of the future will be more about technology.
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Post time: Jul-19-2022