Classification and models of DC motors for electric forklifts
Electric forklift motors are devices that convert electrical energy into mechanical energy. According to different power sources, they can be divided into two categories: AC motors and DC motors. As the prime mover of loading and unloading machinery, electric motors are widely used in gantry cranes, electric hoists, belt conveyors, and electric handling vehicles. AC motors have the advantages of simple structure, easy manufacturing, low price, reliable operation, convenient maintenance, and high efficiency. Its disadvantage is that the power factor is low. During operation, it needs to absorb reactive current from the power grid to establish the magnetic field, and the power factor is less than 1. DC motors have good starting performance and speed regulation performance, combined with mechanical characteristics that can better meet the requirements of working machinery, and are widely used in situations such as electric traction and lifting equipment that require a large speed regulation range and high accuracy. Due to the fact that both electric forklifts and electric tractors currently use DC motors, this section mainly introduces the structure and working principle of DC motors.
The DC motor of electric forklifts can be divided into separate excitation, series excitation, parallel excitation, and compound excitation according to different excitation methods. As shown in the following figure:
The excitation winding WE of a separately excited DC motor is not connected to the electrical winding WA, and the excitation winding is powered by an independent DC power source,
The excitation winding WE of a series excited DC motor is connected in series with the armature winding WA, and the current in both windings is the same,
The excitation winding WE of a parallel excited DC motor is connected in parallel with the armature winding WA, and the two windings are electrically equal,
A compound excitation DC motor has two sets of excitation windings WE and WE, one of which is connected in series with the armature winding WA, and the other is connected in parallel with the armature winding WA and WE. Electric motors with different excitation methods have different mechanical characteristics. Select the corresponding excitation method for the DC motor according to the requirements of the production machinery. The series excited DC motor has the hyperbola (soft) mechanical characteristics, which can obtain greater torque at low speed and higher speed at light load. Therefore, the battery forklift and tractor use series excited DC motor.
According to the different functions of electric forklifts, DC motors can be divided into traction motors, lifting motors, and steering motors. Their working principle is roughly the same, but there are differences in power size and excitation method.
There is a nameplate on the DC motor indicating its model and main technical parameters, providing a basis for the use and selection of the motor.
1. Nameplate. According to national standards and technical requirements during use, the manufacturer has specified the rated working condition of the motor, and the various values indicating the rated working condition are called fixed values. Generally, the rated capacity (power) PN (kW) is marked on the motor nameplate; Rated voltage U (V); Rated electricity (A); Rated speed (r/min); The working quota and temperature rise, etc., for separately excited DC motors, the excitation voltage should also be indicated.
2. Model of DC motor. There are many types of DC motors used in electric forklifts and electric traction vehicles, mainly including ZQ, ZXQ, ZQD, ZZ, ZZY, etc. The specific meaning of its model is shown in the following figure：
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