An electric forklift refers to a loading and unloading machine powered by a battery and powered by an electric motor. Compared with internal combustion forklifts, it has the characteristics of no pollution, low noise, and easy operation. It is especially suitable for closed caverns with high temperature and humidity requirements, workshops with poor ventilation, and other places with high environmental requirements.
The development of electric drive and control systems is basically accompanied by the whole process of the development of electric forklifts. From the perspective of time, it has roughly experienced the following four stages of development. Next, electric forklift manufacturers will tell you about it.
The initial electric forklifts were all driven by DC excitation motors, and the speed control of the motors was realized by connecting resistors, changing the terminal voltage of the battery pack, or changing the magnetic flux of the motor's magnetic field. At present, it is occasionally seen on earlier electric forklifts, which are basically eliminated products.
In the drive and control system of battery handling machinery in the 1970s, electric forklift manufacturers told everyone that in China, the electric machinery used in the early 1980s was a mainstream product. The motor is still driven by series excitation and true current, and the control of the motor uses a thyristor new wave device, but the control of the wave device is mainly based on discrete components or a small number of integrated circuits.
The driving and control system of electric forklift in the 1980s. This generation of electric pallet trucks is still driven by a DC motor, although a thyristor chopper is also used.
However, the manufacturer of the electric forklift told everyone that it uses a microprocessor to control the gradient, and connects it with an external unit. It can set the load type and performance parameters of the controller, and perform fault diagnosis on the controller. Test and introduce regenerative braking control function.
The speed control system of the new generation of electric forklifts is a foreign product in the 1990s. It uses power semiconductor devices with higher operating frequency-MOSFET tubes to form the wave controller of the DC motor.
Because the MOSFET tube is used as the variable current control device, the gradual wave control circuit is simplified, and the voltage drop is reduced when the tube is turned on, and the heat is less: due to the increase in the operating frequency (up to 15kHz or higher), the motor works more smoothly. Shock load reduction: The control of the chopper adopts micro-processing. In addition to setting performance parameters and realizing regenerative braking and other controls, it also has protection functions such as overvoltage, overcurrent, and overheating, and has a fault self-diagnosis function. . Electric forklift manufacturers tell everyone that this type of speed controller is basically installed on the new generation of battery forklifts.
