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4.2 Electrical system of direct current driving electric forklift truck (Fig.2-42)
(Fig.2-42)
4.2.1 Forklift traction is AC variable-frequency motor, steering is AC variable-frequency motor
controller, the dashboard display screen and AC drives adopes products from Curtis, the world's
leading supplier of electric vehicle system in the United States. The adopted AC
variable-frequency motor is high efficient, durable and maintenance free, basically because it has
no DC motor commutator (commutator can limit the acceleration performance of truck, especially
in high speed situation, it will limit braking torque), so its accelerating ability is faster. Controller is
used for ecectric truck which use CANopen protocol controller for communication, through its
analog and digital I/O and communications devices, it is very suitable for management of forklift
movement, I/O operation, control and information display, it can discharge of battery monitoring,
with all kinds of protection function. Dashboard display can show many data, undertake factory or
user setting, can input multiple functions such as user commands.
4.1.2 Main functions and settings
Safe and high efficient working performance and complete operating performance of electric
forklift can be achieved by setting correctly each motor technique data and control technique data
and function value of controller.
1. The creeping speed of electric forklift can be set,the electric forklift work for a long time
under a low speed,through creeping speed seting function of controller.
2
、
Acceleration can be set. Acceleration is the sense of softness or hardness of accelerating
padal when operating electric forklift. By setting rate of rate,forklift can meet the need of
accelerating operation under different working condition.
3
、
Plug braking and regenerative braking. In the course of travelling,there appears,when
reversing direction rod,plug brake signal which,through the controlling of motor driver to pulling
motor,presents a brake moment so as to brake the vehicle.The amount of brake power can be
controlled by accelerating pedal. A proper setting of maximum brake power can ensure to brake
electric forklift smoothly under different speed.Regenerative brake is,under the condition that the
vehicle speed is higher than the rated value of accelerating pedal,generated by the controlling of
controller. The brake power can transfer to electric power and present back to battery.Especially
when the vehicle is coasting downwards slop,in order to properly reduce the speed,regenerative
