Wiring, debugging points and parameter settings of inverter container loaders

Frequency converter is a common automatic control device in the field of industrial control, with stable and reliable performance. Frequency converter applied to container loading and unloading system can greatly improve its operation performance and reliability, and is currently an ideal design mode for container loading and unloading system.

1. Introduction

Container handling machine is one of the special handling equipment for containers. It can be used for loading, unloading, transshipment and stacking of 20ˊ and 40ˊ international standard containers. Its operating height can reach "stack six over seven". In order to improve the starting torque, traditional container handling machines use winding asynchronous motors to drive, and change the speed of the rotor series resistance through the operation of the drum cam controller. With the development of power electronics technology and the emergence of vector control technology, people now generally use frequency converters as speed control power supplies, replace the original winding asynchronous motors with multi-pole variable frequency asynchronous motors, and use PLC as a control device for contactless control. This improves the speed regulation performance and increases the reliability of the system. This article takes the successful application of Xin Kerui Electric SC890 in Penglai Jutao Marine Engineering Heavy Industry Co., Ltd. as an example to explain the variable frequency speed regulation process of container handling machines.

2. System Introduction

2.1 Composition of the operating mechanism of container handling machine.

It mainly consists of three parts: trolley towing system, small car towing system and hook towing system.

(1) The trolley towing system tows the entire crane to move left and right along the direction of the workshop (with the driver's sitting direction as a reference)

(2) The trolley towing system drags the hook and the weight to move back and forth along the bridge.

(3) The hook drag system drags the heavy object to make an up and down movement to lift or lower it. The following is an introduction to the hook drag system.

2.2 Load characteristics

The operating mechanism of container loaders is a constant torque load, and its hook drag system is a potential load. When the hook lifts a heavy object and lowers it or decelerates rapidly, the motor is in a regenerative braking state. The electric energy needs to be fed back to the grid through a feedback device or consumed in a braking resistor to prevent bus voltage overshoot and inverter overvoltage.

3. Control requirements

3.1 The hook dragging system requires large starting torque and smooth starting operation. It should be able to realize forward and reverse operation and have multiple protections such as overload, limit, and current limit.

3.2 The hook dragging system is prone to the problem of "hook slipping" during the starting and stopping process.

Since the action process of the brake from clamping to releasing, and from releasing to clamping takes time (about 0.6s), the generation or disappearance of the motor torque is immediately reflected at the moment of power on or off. Therefore, it is very easy to have problems in the coordination of the brake and the motor. If the motor is powered on and the brake is not released, it will cause serious overload of the motor; on the contrary, if the motor is powered off and the brake is not clamped, the heavy object will slide down, that is, the so-called "hook slipping" phenomenon. Therefore, corresponding preventive measures should be taken.

3.3 The hook dragging system must have a mechanical brake device (mechanical brake). When a heavy object is suspended in the air and a sudden power outage occurs, if a mechanical brake device is not installed, the heavy object will be in danger of sliding down. Therefore, a brake must be installed on the hook motor shaft. Commonly used ones include electromagnetic brakes and hydraulic electromagnetic brakes.

4. System composition and control principle

4.1 System composition

4.1.1 Selection of frequency converter.

The trolley (translation mechanism) towing system of the container loader does not have high requirements on system performance. In order to save costs, the general inverter SC500 with V/F control mode can meet the requirements. (This article is simple); the loader hook (lifting mechanism) towing system requires higher starting torque and speed regulation performance, and a vector control inverter must be used. This article uses the SC890 series vector inverter. The SC890 series inverter has the following features:

4.1.1.1 Starting torque: 0.5Hz/150% (SVC) without PG vector control; 0Hz/200% (VC) with PG vector control (zero speed full torque function, also known as zero servo function, that is, zero speed means the motor can still output 200% of the rated torque to stop the heavy object in the air).

4.1.1.2 Overload capacity: 150% rated current for 60s; 180% rated current for 10s

4.1.1.3 Speed ​​ratio: vector control without PG: 1:100; vector control with PG: 1:1000

4.1.1.4 Speed ​​control accuracy: vector control without PG: ±0.5% of maximum speed; vector control with PG: ±0.1% of maximum speed.

4.1.1.5 The frequency + torque combined brake control logic ensures that the system is safer and more reliable.

The power of the hook lifting motor is: 75kw. In order to ensure sufficient starting and running torque, the capacity of the inverter is enlarged by one specification. Xinkerui SC890-090G/110P-4T inverter is selected. In order to save costs and simplify the control system, this system adopts a PG-free vector control method.

4.1.2 Selection of PLC and HMI

FX2N-40MR from Mitsubishi of Japan; MT506LV from "Wei Lun" of Taiwan

4.1.3 Selection of brake unit

The inverter's braking unit should be increased by one level to allow for a larger braking current and shorten the braking process; the rated power of the braking resistor should be doubled. Therefore, the 150A braking unit of Xin Kerui Electric: SDU-150-4, and the braking resistor selection: 6Ω/20KW (1 piece) are selected.

4.2 System Control Principle

4.2 System control principle description

4.2.1 The main switch, overload, limit switch and inverter relay output signal 1 (fault output) are used as the input signal of Mitsubishi FX2N plc.

4.2.2 The output signal of PLC controls the multi-function input terminal of the inverter (controls the inverter's forward and reverse rotation, multi-speed, fault reset, emergency stop, etc.) and the on and off of the main power supply circuit.

4.2.3 The touch screen and PLC are connected via the RS422 serial interface. The interface program in the PLC sets up a data reading area and related status flags for the touch screen in the PLC to monitor the height, load, operating status, fault information, etc. of the main hook.

(1-1)

System control schematic diagram

5. Inverter wiring, debugging points and parameter settings

5.1 Inverter wiring instructions

5.1.1 The inverter multi-function input terminals X1-X7 and HDI are used to control the inverter's start, stop, forward, reverse, multi-speed, fault reset and emergency stop.

5.1.2 Relay 1 output is used as "fault output"; Relay 2 is used as "brake/release" output (frequency + torque combination).

5.1.3 The SDU-150-4 brake unit and brake resistor are connected in parallel on the DC bus of the inverter to consume the energy generated during the downward movement of the hook and realize the four-quadrant operation of the inverter.

(1-2)

Inverter wiring diagram

5.2 Debugging points

5.2.1 Static self-learning. When using vector control without PG, the control performance of the inverter is based on the accuracy of the motor model. Therefore, before running the motor for the first time, it is necessary to self-learn the motor parameters:

Set the function parameter F0.01 to 0 (operation panel command channel), and other parameters should be based on the factory parameters. Then enter the following parameters according to the motor nameplate parameters:

F2.00= 0 G-type inverter F2.01= 75 Motor rated power

F2.02= 50 Motor rated frequency F2.03= 585 Motor rated speed

F2.04= 380 Motor rated voltage F2.05= 163 Motor rated current

3. Set the function parameter F0.16 to 1 (since it is impossible to completely detach from the load, static self-learning is adopted), and then press the RUN key on the keyboard panel, the inverter will automatically calculate the following parameters of the motor:

F2.06: Motor stator resistance F2.07: Motor rotor resistance F2.08: Motor stator and rotor inductance

F2.09: Motor stator and rotor mutual inductance F2.10: Motor no-load current

When the inverter P0.16 is set to "2" and confirmed, the keyboard panel displays "TURE" to indicate that it has entered the self-learning state. Then press the RUN key on the keyboard panel, the "RUN" indicator light on the keyboard panel will light up, and the motor will rotate, indicating that it is in self-learning. When the "RUN" indicator light on the keyboard panel goes out and the keyboard panel displays "50.00", it means that the self-learning is completed.

5.2.2 Control of brake and release. The vector control mode without PG cannot reach the rated output torque when running at "0" Hz, so it is necessary to use an FDT level (relay 2 output) function to improve the control function. That is: set a suitable FDT level detection value, so that the inverter will open the mechanical brake device only after running at a certain frequency. If the FDT level detection value is set too high, it is easy to trip the "overload" or "overcurrent" fault; if the FDT level is set too low, it cannot lift heavy objects. The final FDT level detection value set here is 2Hz. If the vector control mode with PG is used, a control signal can be output to open the mechanical brake device when running at "0" Hz.