Introduction of tower crane

Tower cranes which originated in Western Europe. A rotating crane with a boom mounted on the top of the tower. The working space is large, mainly used for vertical and horizontal transportation of materials and installation of building components in building construction.

Basic composition

The main components include: metal structure, working mechanism and electrical system.Metal structures include: tower body, boom and base. Working institutions include: lifting, luffing, turning and walking. Electrical systems include: motors, controllers, power distribution cabinets, connecting lines, signals, and lighting.

Working principle

  Big Car running mechanism: used to drag the entire crane to make lateral movement along the construction site, consisting of electric motor, brake, speed reducer and wheel. Trolley running mechanism: used to drag the hook and heavy objects to make longitudinal movement along the bridge, and also consists of electric motor, brake, speed reducer and wheel. Lifting mechanism: A lifting movement for dragging heavy objects to ascend or descend, consisting of a motor, a speed reducer, a reel and a brake. A large starter (over 10T) has two lifting mechanisms; the "main hook" and " The secondary hook "cannot lift the cargo at the same time.
  Slewing mechanism: The dragging arm is rotated around the axis. Due to the deviation prevention, it is usually composed of a double motor, a speed reducing mechanism and a brake. The luffing mechanism: the amplitude refers to the horizontal distance from the center line of the tower crane to the center line of the hook. The luffing action refers to the round-trip operation of the trolley on the tower crane. Through the operation of the car, the range of the hook cover can be adjusted

Industry application requirements

1）Low-frequency large torque output, which satisfies the low-frequency opening and closing;

2）Super overload capability, when the load fluctuates, it will not cause fault shutdown

3）Wide voltage range to meet the normal fluctuations in field voltage;

4）Rich system protection function, which can timely feedback the equipment failure information caused by operation errors to ensure the safe operation of the system;

5）A variety of lifting industry-specific functions, with system given and feedback signals, to complete different lifting actions.

Industry status

Traditional control methods. Tower crane is a kind of lifting machine widely used on construction sites. The traditional control method uses the method of AC winding type motor string resistance to start and speed, which has the following disadvantages:

1） Long-term heavy-duty operation, frequent positive and negative, and large inrush current;

2）The failure rate is high, the slip ring, carbon brush and contactor of the motor are often damaged, and the motor resistance burns out sometimes occurs;

3） the circuit is complicated, the bearings of the slewing mechanism often need to be replaced;

4）low efficiency, because the main elevator structure is mostly operated by two motors on one axis, the high-speed motor is in working state, then the low-speed motor is in the braking state, always in the contradiction between one work and one brake; the safety factor is low When the speed is changed from fast to slow, the mechanical impact is large, and the toothing phenomenon often occurs.

Difficulties in frequency conversion applications

1）The imported inverter is still relatively expensive, but the domestic inverter technology is not closed;

2）once the inverter has a problem, generally can not repair, most can only be replaced, the frequency conversion speed is too high, generally small and medium tonnage lifting mechanism application is less, large tonnage is more;

3）the domestic inverter control hoisting mechanism, due to insufficient low-frequency torque, most of them have the problem of starting vibration, there will be a hook phenomenon during the start-stop process;

4）Many products are complicated to debug, involve too many parameters, and cannot monitor device data information from time to time. Fault problems sometimes occur, and control operation is extremely unstable.

 CUMARK product advantages

1）Start without reversal, excellent open-loop closed-loop vector control performance

2）Low frequency and large torque output, minimum load current

3）Lifting industry professional software, control logic, excellent control effect

4）High degree of protection (IP40), independent air duct design to better adapt to the harsh environment

5）Standard Chinese LCD smart keyboard, friendly man-machine interface, quick and easy to debug and maintain

ES series application case and effect

  The ES850 high performance vector inverter + three-phase asynchronous motor control is adopted in the field. The system is equipped with a lifting motor, a swing motor and a luffing motor. The control system PLC receives the console command, detects various sensor signals, executes the set program, and sends the start and stop operation control and the speed reference command to the inverter to achieve perfect control operation effect.

  The ES850 is used in hoisting, swinging, and trolley luffing mechanisms. The invention solves the problem that the low frequency torque is insufficient, the shutdown is easy to alarm, and the control effect is unstable.

Advantages:

1）The response speed is fast, the low-frequency and large-torque output, and the vibration phenomenon at the start-up is better suppressed; the zero-speed brake and the opening of the brakes completely eliminate the occurrence of slippage and backflushing.
2）Accurate current output makes the matching between load, output power and running speed reach the ideal state. Even under the condition of mechanical tolerance, it can run at high speed and improve the efficiency of the feeding operation.
3）the frequency conversion speed regulation can achieve stable start and stop braking, small mechanical impact, can extend the service life of the tower crane machine.
4）high reliability, closed circuit structure and multi-layer three anti-paint thickening process, the protection level reaches IP40, more suitable for the harsh environment in the field.
5）motor output power optimization, while improving work efficiency, can reduce energy consumption, resulting in good economic benefits.
6）precise frequency conversion control scheme can limit the overload or over-range operation, prevent the operator from rough construction and barbaric operation from the control system, and effectively protect the normal operation of the working mechanism.
7）Wide voltage range (±20%), which satisfies the normal operation of large fluctuations in the field voltage.
8）The load weight that can be increased by the tower crane is related to the amplitude variation. After the frequency conversion speed regulation is used, the automatic load control at different amplitudes can be realized through the linkage of the trolley luffing mechanism and the lifting mechanism.
9）Using the speed limit function of the inverter, it can avoid high-speed tension when the wire rope is slack, reduce the loss of the wire rope, and prevent serious accidents caused by the wire rope breaking.

10）The industrial-grade large-size intelligent LCD keyboard displays various operating parameters, which is convenient for the operator to grasp the running status information from time to time, and can realize remote control, fault diagnosis and parameter correction.