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The vector control inverter is applied to the port crane


2021-02-08

I. Overview

    This article describes the advantages of variable frequency speed regulation technology and its application in door machines, and focuses on the comparison of the principles, advantages and disadvantages of two-level control and three-level control, and describes the new characteristics of the inverter static self-learning , And analyzed and prospected the application prospect of three-level control technology in door operator.

 

2. Frequency conversion transformation of door electrical control system

    Port gantry cranes (hereinafter referred to as gantry cranes) are general-purpose port loading and unloading cranes for loading and unloading general bulk cargo at the front of port terminals. They are widely used in various sea ports and inland wharfs. Most of the old door cranes in ports use rotor series resistance speed regulation for stepwise speed regulation. Therefore, the impact of the whole machine is large, especially when the vibration is severe during parking and starting, which accelerates the wear of the steel structure of the door crane and also makes the maintenance of the workers. The amount is greatly increased. In recent years, with the improvement of port automation level, the application of AC frequency conversion speed regulation technology in door cranes has become more and more common. According to statistics, frequency conversion technology has been added to the newly equipped door cranes in all ports in the past two years. In this case, the frequency conversion transformation of the old door electrical control system is particularly urgent.

 

3. The advantages of door machine frequency conversion control

3.1. Since the power of the hoisting mechanism motor is generally large, the one-time investment in the transformation of the hoisting mechanism is too high; some process requirements of the large car are relatively simple, and the effect after the frequency conversion transformation is not very obvious, so the current domestic old door machine frequency conversion transformation is mostly Only change the width and rotation mechanism. The luffing mechanism is mostly controlled by a winding motor to drive the luffing of the rack, which is a stepped speed regulation of conventional control. Therefore, the impact of the luffing mechanism increases when the luffing mechanism is in operation, especially when the vibration is severe during parking and starting, which causes the reducer to seal Lax, oil leakage intensifies, accelerates the wear of the mechanism, and also increases the amount of maintenance. The rotating mechanism is mostly column type, and the supporting weight of the slewing bearing is heavier, which causes the swing mechanism of the door machine to shake during the braking process, which has a certain impact on the life of the steel structure; and the door machine has a relatively high brake pedal force. Large, thus causing operator fatigue. Through the analysis of the above reasons, we believe that the impact caused by the luffing and rotating mechanism is caused by the inability to absorb the kinetic energy generated during starting and braking. We have solved the above problems by introducing a frequency conversion speed control system.

3.2. The frequency converter can stepless speed regulation in a wide range, and the acceleration and deceleration time can be set freely according to the needs; good low-speed torque characteristics enable the motor to obtain a sufficiently large and smooth acceleration when starting and accelerating; braking unit And the connection of the braking resistor enables the motor to obtain sufficient braking torque when decelerating and stopping. The above-mentioned characteristics of the frequency converter ensure that the frequency conversion speed regulation system has a good speed response performance.

3.3. According to the current situation of port cranes, we generally do not replace the original motor when adopting frequency conversion speed regulation, but only short-circuit the winding motor rotor circuit. Because the contactor used for stepwise removal of resistance speed regulation is removed, stepless and non-contact control of speed regulation is realized; and because the inverter itself is a high-reliability general standard equipment, the failure rate is extremely low, which greatly reduces The failure rate of the equipment reduces the workload of the door operator maintenance personnel and indirectly improves the work efficiency. Because of the functional design of the Yaskawa inverter for the crane industry, through the logical judgment of the PLC part, it truly guarantees that the motor can brake at "zero speed", and realizes the smooth starting and braking of the inverter, thereby reducing the mechanical impact of various mechanisms. The impact on the mechanical part of the door machine during starting and braking prolongs the service life of the mechanical part of the door machine. Because the inverter adopts AC-DC-AC control mode and is equipped with incoming line reactors, the average power factor during heavy-duty operation can reach over 85%, which greatly exceeds 60% of ordinary electronic control door machines, and the energy saving rate can reach 30%.

 

4. The principle of the new three-level control inverter and its application prospects in ports

4.1. Due to its professional advantages in the crane industry and successful cases in port applications for many years, Yaskawa inverters have become the first choice for inverter transformation of portal cranes. According to statistics, at present, more than 90% of frequency conversion door machines nationwide use Yaskawa frequency converters. With the continuous advancement of variable frequency speed regulation technology, Yaskawa has officially launched the real current vector control type G7 series inverter with three-level control in the Chinese market. It is currently the only low-voltage inverter with three-level control in the world. .

4.2. As we all know, the inverters we see in the inverter market now all adopt the "2-level control" method (including Yaskawa’s G5 series inverters). This type of inverter requires the motor to be equipped in principle. It is a variable frequency motor. But in fact, the motors used in almost all door machines that need to be modified are ordinary winding motors. This kind of motor not only has a larger starting current than a variable frequency motor of the same power, but also has a lower insulation level than a variable frequency motor (inverter motors are generally Class F, while ordinary winding motors are generally B).

I. Overview

    This article describes the advantages of variable frequency speed regulation technology and its application in door machines, and focuses on the comparison of the principles, advantages and disadvantages of two-level control and three-level control, and describes the new characteristics of the inverter static self-learning , And analyzed and prospected the application prospect of three-level control technology in door operator.

 

2. Frequency conversion transformation of door electrical control system

    Port gantry cranes (hereinafter referred to as gantry cranes) are general-purpose port loading and unloading cranes for loading and unloading general bulk cargo at the front of port terminals. They are widely used in various sea ports and inland wharfs. Most of the old door cranes in ports use rotor series resistance speed regulation for stepwise speed regulation. Therefore, the impact of the whole machine is large, especially when the vibration is severe during parking and starting, which accelerates the wear of the steel structure of the door crane and also makes the maintenance of the workers. The amount is greatly increased. In recent years, with the improvement of port automation level, the application of AC frequency conversion speed regulation technology in door cranes has become more and more common. According to statistics, frequency conversion technology has been added to the newly equipped door cranes in all ports in the past two years. In this case, the frequency conversion transformation of the old door electrical control system is particularly urgent.

 

3. The advantages of door machine frequency conversion control

3.1. Since the power of the hoisting mechanism motor is generally large, the one-time investment in the transformation of the hoisting mechanism is too high; some process requirements of the large car are relatively simple, and the effect after the frequency conversion transformation is not very obvious, so the current domestic old door machine frequency conversion transformation is mostly Only change the width and rotation mechanism. The luffing mechanism is mostly controlled by a winding motor to drive the luffing of the rack, which is a stepped speed regulation of conventional control. Therefore, the impact of the luffing mechanism increases when the luffing mechanism is in operation, especially when the vibration is severe during parking and starting, which causes the reducer to seal Lax, oil leakage intensifies, accelerates the wear of the mechanism, and also increases the amount of maintenance. The rotating mechanism is mostly column type, and the supporting weight of the slewing bearing is heavier, which causes the swing mechanism of the door machine to shake during the braking process, which has a certain impact on the life of the steel structure; and the door machine has a relatively high brake pedal force. Large, thus causing operator fatigue. Through the analysis of the above reasons, we believe that the impact caused by the luffing and rotating mechanism is caused by the inability to absorb the kinetic energy generated during starting and braking. We have solved the above problems by introducing a frequency conversion speed control system.

3.2. The frequency converter can stepless speed regulation in a wide range, and the acceleration and deceleration time can be set freely according to the needs; good low-speed torque characteristics enable the motor to obtain a sufficiently large and smooth acceleration when starting and accelerating; braking unit And the connection of the braking resistor enables the motor to obtain sufficient braking torque when decelerating and stopping. The above-mentioned characteristics of the frequency converter ensure that the frequency conversion speed regulation system has a good speed response performance.

3.3. According to the current situation of port cranes, we generally do not replace the original motor when adopting frequency conversion speed regulation, but only short-circuit the winding motor rotor circuit. Because the contactor used for stepwise removal of resistance speed regulation is removed, stepless and non-contact control of speed regulation is realized; and because the inverter itself is a high-reliability general standard equipment, the failure rate is extremely low, which greatly reduces The failure rate of the equipment reduces the workload of the door operator maintenance personnel and indirectly improves the work efficiency. Because of the functional design of the Yaskawa inverter for the crane industry, through the logical judgment of the PLC part, it truly guarantees that the motor can brake at "zero speed", and realizes the smooth starting and braking of the inverter, thereby reducing the mechanical impact of various mechanisms. The impact on the mechanical part of the door machine during starting and braking prolongs the service life of the mechanical part of the door machine. Because the inverter adopts AC-DC-AC control mode and is equipped with incoming line reactors, the average power factor during heavy-duty operation can reach over 85%, which greatly exceeds 60% of ordinary electronic control door machines, and the energy saving rate can reach 30%.

 

4. The principle of the new three-level control inverter and its application prospects in ports

4.1. Due to its professional advantages in the crane industry and successful cases in port applications for many years, Yaskawa inverters have become the first choice for inverter transformation of portal cranes. According to statistics, at present, more than 90% of frequency conversion door machines nationwide use Yaskawa frequency converters. With the continuous advancement of variable frequency speed regulation technology, Yaskawa has officially launched the real current vector control type G7 series inverter with three-level control in the Chinese market. It is currently the only low-voltage inverter with three-level control in the world. .

4.2. As we all know, the inverters we see in the inverter market now all adopt the "2-level control" method (including Yaskawa’s G5 series inverters). This type of inverter requires the motor to be equipped in principle. It is a variable frequency motor. But in fact, the motors used in almost all door machines that need to be modified are ordinary winding motors. This kind of motor not only has a larger starting current than a variable frequency motor of the same power, but also has a lower insulation level than a variable frequency motor (inverter motors are generally Class F, while ordinary winding motors are generally B).