Weichuang Electric AC80 Special Inverter Renovation Plan for Crane

I. Introduction

With the continuous improvement of the speed regulation performance of cranes for industrial production, the commonly used conventional crane speed control methods, such as the common disadvantages of the wound rotor asynchronous motor series resistor speed regulation, thyristor stator voltage regulation and cascade speed regulation, are common. Winding rotor asynchronous motors have collector rings and brushes. They require regular maintenance. Faults caused by collector rings and brushes are common. In addition, a large number of relays and contactors are used, resulting in large on-site maintenance. The failure rate of the speed system is high, and the integrated technical indicators of the speed control system are poor, which can no longer meet the special requirements of industrial production.

The wide application of AC variable frequency speed regulation technology in the industry has provided a brand-new solution for large-scale, high-quality speed control of AC asynchronous motor-driven cranes. It has high-performance speed regulation indicators and can use the squirrel-cage asynchronous motor with simple structure, reliable operation and convenient maintenance, and is highly efficient and energy-saving. Its peripheral control circuit is simple, maintenance workload is small, protection monitoring function is perfect, and its operating reliability is relatively high. The traditional AC speed control system has greatly improved. Therefore, the adoption of AC variable frequency speed regulation is the mainstream of crane AC speed control technology development.

After AC frequency conversion speed regulation technology is applied to cranes, it can bring the following remarkable economic benefits and safety and reliability compared with the conventional series wound resistance speed regulation system of the wound rotor asynchronous motor widely used in the market:

(1) Cranes using AC variable frequency speed control technology Due to the hard mechanical characteristics of the motor driven by the Inverter and the advantages of precise positioning, the phenomenon that the speed of the motor changes with the change of the load of the conventional crane does not occur, and the productivity of loading and unloading operations can be improved. .

(2) The frequency conversion crane runs steadily, the start-up and braking are gentle, the vibration and impact of the whole machine are obviously reduced, the safety is improved, and the life of the mechanical part of the crane is prolonged.

(3) The mechanical brake operates when the motor runs at a low speed. The brakes of the main hook and the large and small vehicles are completed by electric braking. Therefore, the service life of the brake pads of the mechanical brake is greatly extended and the maintenance cost is reduced.

(4) Using a squirrel-cage asynchronous motor with a simple structure and high reliability to replace the wound rotor asynchronous motor to avoid damage to the motor or failure to start the motor due to poor contact due to abrasion or corrosion of the collector rings and brushes.

(5) The number of AC contactors is greatly reduced, and the main circuit of the motor realizes the non-contact control, avoiding the damage caused by the frequent operation of the contacts of the contactor and the damage of the motor due to the burning of the contacts of the contactor.

(6) AC variable frequency speed control system can flexibly adjust the speed and acceleration/deceleration time of each gear according to the situation on the site, making the variable crane operation flexible and on-site adaptability.

(7) AC variable frequency speed control system is a high-efficiency speed control system, with high operating efficiency and small heat loss, so it saves a lot of power compared to the old speed control system.

(8) The frequency converter has perfect protection, monitoring and self-diagnosis functions. If combined with PLC control, it can greatly improve the reliability of the frequency conversion crane electronic control system.

Second, the characteristics of crane operation

(1) The crane should have a large starting torque, usually more than 150% of the rated torque. If overload is considered, at least 200% of the rated torque should be provided during acceleration.

(2) Due to the presence of mechanical brakes, in order to smoothly switch the output torque of the inverter and the braking torque of the mechanical brake, no slipping phenomenon occurs, and the control sequence of the inverter start signal and the mechanical brake action signal must be fully studied.

(3) When the hoisting mechanism is running down or the deceleration of the translation mechanism is abrupt, the motor will be in a state of regenerative power generation, and its energy will be fed back to the power source side. The regenerative energy must be processed according to the site conditions.

(4) When the lifting mechanism grabs heavy objects to leave or touch the ground, the load changes drastically, and the inverter should be capable of controlling the impact load smoothly.

三、Introduction of Flextronics AC80 Crane Inverter

1, the main functions and features

Weichuang AC80 Crane Inverter is a high-performance vector inverter specially designed for lifting industry by Shenzhen Weichuang Electric Co., Ltd. It is used for lifting, pitching, luffing, carts, trolleys, swings, etc. of various types of cranes. Grab and other institutions of AC stepless speed regulation. The main functions and features are as follows:

(1) Wide range of speed regulation, which can realize operations with precise control positioning requirements;

(2) The function of soft start and soft stop reduces the impact of mechanical transmission, can significantly improve the bearing performance of the steel structure, and extend the service life of the crane;

(3) Brake logic control and monitoring, accurate brake opening and closing control sequences, real-time status feedback through brakes and pre-torque compensation to ensure the safety and reliability of the control;

(4) Light-load speeding, 2×speed operation when the crane is hooked or lightly loaded, improving handling efficiency. The light-load speed-up function is mainly applied to cranes with higher lifting heights to shorten the time to improve handling efficiency;

(5) The control loop power supply and the main loop power supply can be separately controlled to improve the safety of the user when debugging, and facilitate fault diagnosis and maintenance.

(6) Support MODBUS communication protocol, can realize the communication connection between many inverters and PLC.

(7) Dangerous speed monitoring, fast stop, and overspeed protection The inverter monitors the running speed of the motor in real time. When the motor speed is greater than the set maximum allowable speed or speed deviation value, the inverter issues a fault alarm and stops output immediately, mechanical brake action. Keep the crane in a safe state.

Fast parking features provide users with the following three options:

Method 1: Parking for electrical brakes;

Method 2: Parking for electrical brakes plus mechanical brakes;

Mode 3: Parking for mechanical brakes.

(8) The pre-excitation function is to automatically perform DC excitation on the motor before start-up to ensure that the motor can quickly provide the starting torque and adjust the excitation time to match the start of the motor with the release time of the mechanical brake to avoid “ Slip hook phenomenon.

(9) Crane operation mode - convenient and flexible

According to different operation modes of the crane, the following modes of operation are provided for the user: joystick mode, remote mode, motorized potentiometer mode, hierarchical joystick given mode, hierarchical remote control given mode, communication given mode, and the like.

2、Brake function description

The Flextronics AC80 Crane Inverter has a built-in logic sequence control function for the mechanical brake. As long as the parameters are set, the problem of mechanical brake logic can be solved. In the application of lifting equipment, there is generally a mechanical brake mechanism, which is mainly taking into account the safety aspects. Lifting mechanism in the moment before and after the mechanical brake mechanism is held, it is easy to cause the phenomenon that the weight descends from the stop state (known as the slip hook), and the slip hook is a safety control link in the design of the bridge crane control system. . When the hook lifting heavy object is stopped in mid air, if it is necessary to make a rising or falling action, the cooperation between the operation of the inverter and the control of the mechanical brake mechanism is very important; The inverter may alarm (overload or overcurrent), and heavy objects may slip. In response to this phenomenon, special inverters for Flextronics AC80 cranes are specially developed to facilitate adjustment. Using AC80 inverter multi-function output terminal can solve this problem.

First set the inverter output terminal Y1 or Y2 as the inverter output frequency level detection signal, set the output frequency level detection to 2Hz, when the crane starts to work in the lifting or lowering, the mechanical brake must be in the inverter running above 2Hz. turn on. When the crane is about to stop when lifting or lowering the work, the mechanical brake must be turned off when the frequency converter is running below 2Hz.

According to the characteristics of the crane load, when the object is lowered, it is in the state of power generation. In order to lower the object when the object is lowered, the energy must be released. This requires the inverter to have a braking unit and to apply energy through the braking resistor. Use up.

3, the scope of application

Weichuang AC80 crane special vector inverter, with excellent torque control performance, widely used in shoreside container cranes (STS), rail container gantry cranes (RMG), tire container gantry cranes (RTG), portal cranes, Shipbuilding gantry cranes, ship loaders, ship unloaders, dumpers, stacker-reclaimers and other types of port machinery, as well as various types of ordinary bridge, portal, tower cranes and lifting machines, bridge cranes and other lifting machinery Lifting, luffing, carts, trolleys, slewing, grabs and other mechanisms of AC stepless speed regulation.

Fourth, the conclusion

Through the use of Flextronics inverters, the old speed control systems have solved the shortcomings of high failure rate, complicated circuits, incapable of smooth speed regulation, and large amount of maintenance. At the same time, they also simplified the design work and led to a new electrical control performance. Steps. Its reliability and advanced nature are unmatched by the old speed control system, and are welcomed by users with its superior performance to price ratio.