Application of Sunwoele VFD (Variable-frequency Drive) in Taizhou Port 40T Portal Crane Hoisting Mechanism

This year, Taizhou Port used PLC and Sunwoele VFD (Variable-frequency Drive) to conduct an electrical upgrade on a second-hand 40T-30M multi-purpose door crane. The lifting mechanism of the machine is configured as 2 sets of identical and independent mechanisms (2 sets of motors, double drums, 4 ropes) for hook and grab operations. The electrical control part is an ordinary relay circuit, and the electrical drive is a winding motor. After the transformation, the frequency conversion motor is used to drive it by VFD (Variable-frequency Drive).

Now we will introduce the selection principle, debugging application process and usage of VFD (Variable-frequency Drive) in the lifting mechanism of the gantry crane:

1. Selection principle of VFD (Variable-frequency Drive)

① Possess vector control technology

This is because the starting torque of the lifting load of the door machine is very large (70%-150% of the rated torque is required), and the starting current cannot be too large (1.2-1.5 times the rated current). The V/F control method of ordinary VFD (Variable-frequency Drive) cannot be realized. The result is either that the motor cannot start and causes a stall or the starting current is too large to cause overcurrent protection. VFD (Variable-frequency Drive) with vector control technology can do this.

Generally speaking, vector control is to imitate the control method of DC motor, decompose the stator current vector of the asynchronous motor into the current component (excitation current) that generates the magnetic field and the current component (torque current) that generates torque and control them separately, so that the asynchronous motor not only matches the DC motor in the speed regulation range, but also can control the torque generated by the asynchronous motor, and realize smooth operation at extremely low speed and high-torque and high-precision speed control.

② With torque following technology

This technology uses one VFD (Variable-frequency Drive) as the main drive in the speed control mode, and the other VFD (Variable-frequency Drive) as the auxiliary drive in the torque control mode. The torque output of the main drive is used as the torque setting of the auxiliary drive, so that the given signal of the auxiliary drive is torque rather than frequency. The auxiliary transmission follows the change of the main transmission torque to achieve the purpose of load distribution control. This control method has high control precision and fast dynamic response. When the load torque of the auxiliary transmission is large, the motor speed is low; when the load torque is small, the motor speed is high; the maximum frequency can be reached when there is no load.

③Precise brake logic sequence control and monitoring

The hoisting mechanism of the door crane is controlled by VFD (Variable-frequency Drive), so that the start and stop of the motor and the opening and closing of the brake should be precisely coordinated to avoid the phenomenon of "slip hook".

④The product has excellent technology, high reliability and considerate and timely service from the manufacturer.

⑤ The product has a lower price

?two. debugging, application process

In view of the above requirements, we selected two HSF600-315KW VFD (Variable-frequency Drive) from Sunwoele Company for the hoisting mechanism. During the debugging and application process, several technical advantages of the VFD (Variable-frequency Drive) are highlighted:

1. Real current vector control, we use its vector control mode with PG, the speed control accuracy reaches ±0.02%, the starting torque, zero speed can reach 150% of the rated torque, the output torque is large, the current is small, and the operation is stable. When lifting heavy parts, the door crane can stop smoothly in the air and restart with ease.

2. Exquisite torque control and torque following technology, which is especially reflected in the grab operation of the portal crane. Our specific application method is: when the door machine is in the grab operation, the opening and closing rope is lifted to close the grab. At this time, the support rope is transferred to the torque control mode. After debugging, it is more appropriate to give the support rope a given value of 1% of the rated torque and a given value of -10% of the motor speed limit. (At this time, the torque direction of the support rope motor is opposite to the speed direction, which is the so-called uncoiler action state), so that the support rope descends with the grab bucket without slack, and at the same time achieves the purpose of deep digging by the grab bucket. When the grab is fully closed and the opening and closing rope is lifted together with the support rope, the given value of the torque of the support rope is changed from 1% of the rated value to the output torque value of the open and close rope (this is a given value of a continuously decreasing dynamic process), and the given value of the speed limit is changed from -10% of the rated value to 120% of the maximum speed value of the open and close rope. At this time, the support rope enters the torque following action state. (At this time, the torque direction of the support rope motor is the same as the speed direction, which is the so-called winder operating state.) At the beginning, the support rope is in an unloaded state, and runs at a speed exceeding the opening and closing rope (the so-called chasing rope). After the two ropes are aligned, the torque distribution is performed. When the torque of the support rope is close to the torque of the opening and closing rope, it is transferred to the speed control mode and enters the next grasping cycle.

This technology has been used very successfully. The driver is easy to operate during the grab operation, which improves the work efficiency. (In addition, the torque control function of HSF600 series VFD (Variable-frequency Drive) is used for the cable reel of cranes such as portal cranes and quay cranes. It can be applied conveniently and quickly, and the control is precise. It is an upgraded product of the existing hysteresis type cable reel products.)

3. Brake control is another key to the success of VFD (Variable-frequency Drive) used in hoisting mechanisms. Sunwoele VFD (Variable-frequency Drive) has as many as 37 multi-function output settings. For example, the zero speed output accurately controls the opening and closing of the brake. We observed that during the long-term heavy operation of nearly 40T grab bucket, the brake wheel has no temperature at all. Nevertheless, to ensure safety