Abstract: This paper mainly introduces the application of the series frequency converter on the master slave drive of the belt sintering machine, and the principle of the master slave power balance mode. The production practice has proved that it fully meets the process requirements and has high reliability.
Keywords: frequency converter; Belt sintering machine; Flexible transmission; Master slave power balance mode
1. Introduction
Sintering is a method of sintering various powdery iron containing raw materials into blocks under incomplete melting conditions by mixing and pelletizing them with proper amount of fuel, flux and water. The main sintering line is hundreds of meters long, and the sintering process on the sintering machine does not last long, and it is completed in dozens of minutes.
The frequency converter has been successfully applied to the flexible drive of the belt sintering machine in a new sintering production line of a casting pipe company in Sichuan. The main technical problems in the application are briefly introduced below.
2. Electrical requirements for flexible drive of belt sintering machine of a casting pipe company in Sichuan
2.1 Transmission device of sintering machine
The transmission device of sintering machine mainly depends on the head sprocket (driving wheel) to transport the trolley from the lower rail to the upper horizontal rail through the head bend, and push the front trolley to move towards the tail. When the adjacent trolley moves to the up and down parallel position, the gap disappears, and the trolley moves one by one.
Fig. 1 Belt Sintering Transmission Device
2.2 Trolley
The belt sintering machine is a closed sintering belt composed of many trolleys, so the trolleys are an important part of the sintering machine. It directly bears the loading, ignition, ventilation, sintering and unloading at the tail of the machine to complete the sintering operation. The trolley is cast into two halves and connected by bolts. Roller bearings are installed in the trolley rollers, and rails are installed on both sides of the trolley.
Fig. 2 Sintering Machine Trolley
(2) When the main drive and the driven motor shaft are flexibly connected through equipment such as transmission belt, a slight speed difference is allowed between the secondary drive and the main drive. As shown in Figure 4, the secondary drive uses speed control; 3. Electrical drive requirements for belt sintering machine
● Two AC asynchronous motors drive the belt sintering machine head sprocket through the gear reducer;
● Speed shall be adjusted by external potentiometer;
● Forward and reverse rotation are required;
● When the belt sintering machine is loaded and started, the load torque is large, and the output starting torque of the motor drive device is required to be large enough to ensure the smooth starting of the belt sintering machine.
● It is necessary to ensure that the output power of these two motors is the same, that is, the power is balanced; Avoid overload or overcurrent fault of motors with large output due to different output power between motors.
4. Application of master slave power balance of frequency converter in belt sintering machine
4.1 Working principle of master slave control of frequency converter
In the master slave application of frequency converter, the main drive is typical speed control, while the slave drive is speed or torque control. Generally, it can be divided into:
(1) When the motor shaft of the main drive and the secondary drive is rigidly connected (gear or chain), there should be no speed difference between the secondary drive and the main drive. As shown in Figure 3, the secondary drive uses torque control to make no speed difference between the transmission units. When it works, it is only responsible for outputting a certain proportion of torque to reduce the load fluctuation of the main drive, and the speed control of the whole drive is completed by the main drive;
(3) In some applications, the slave drive requires both speed control and torque control. In this case, the free switch between speed control and torque control is completed through a digital input terminal of the slave.
Fig. 3 Torque control used in slave drive Fig. 4 Speed control used in slave drive
4.2 Application of master slave power balance of field frequency converter
The communication can be 485 communication or CAN communication, and the actual field use is CAN communication.
5. Application effect and customer evaluation
Through long-term load operation test of the flexible drive of the belt sintering machine, the specific effects of the whole sintering machine system are as follows:
● The running speed of sintering machine trolley is 1.0~3.0m/min, which fully meets the requirements of production on the running speed of the trolley;
● The current difference between the host and the slave is controlled at about 0.5A, and the current of the two motors does not oscillate;
● The drive of the belt sintering machine adopts the frequency converter for the master-slave power balance control, so as to realize the safe soft start and soft stop of the trolley, stable operation and load distribution balance.
6. Conclusion
The successful application of the master slave power balance mode of the frequency converter in the trolley drive of the metallurgical belt sintering machine not only solved the power balance problem between the two motors, but also improved the field automation level, which played a very positive role in improving the production capacity of the plant and ensuring safe production.