Rotary machine multi-motor power failure synchronous brake control system
In the cotton spinning process, the main function of the roving frame is to make a certain drafting of the sliver so that the sliver can reach a certain draw ratio and be made into a certain winding form, which is convenient for storage and handling, and is suitable for the spinning machine. Feeding. At present, the roving process roving machine automation system structure is mainly divided into three major schemes: first, using industrial control computer, board, frequency converter; second, touch screen, PLC, frequency converter; third, touch screen, single-chip module, frequency converter. But all three system solutions must face a problem: that the power failure requires multiple motors to stop synchronously. At present, it is commonly used that the frequency converter enters the braking state and generates regenerative energy to ensure that the motor stops synchronously.
2 external busbar capacitor energy storage synchronous braking design
2.1 principle design
According to the general inverter principle, the DC bus capacitor is used to filter out the AC component of the rectifier and stabilize the inverter supply voltage. For multi-motor independent variable frequency drive roving frames, the busbar capacitors have the potential to utilize regenerative braking excitation energy by utilizing stored electrical energy during accidental power-down. Since the standard bus capacitor capacity is usually only to meet the filtering and voltage regulation, it is difficult to meet the power demand of the power-off braking. A synchronous large-capacity bus capacitor energy storage synchronous braking scheme is proposed. The external capacitor will cause a huge starting current impact on the rectifier of the inverter. The soft start protection design is realized by the roving frame PLC. The principle is similar to the internal bus capacitor connection start protection resistor of the inverter. For the synchronous design of busbar capacitor energy storage, Delta B series inverters have customized the software for the application characteristics of the roving frame.
3 external bus capacity calculation
3.1 Calculation purposes
(1) Calculate the amount of external capacitor required to ensure that the full-load roving machine can stop synchronously when power is lost.
(2) Design an external soft-start circuit to ensure that the impact of power-on is reduced when the inverter capacitance is increased.
3.2 Calculation steps
(1) Analysis of capacitor port voltage curve
4 soft start protection resistor design
4.1 Soft Start Principle
In any voltage-type inverter, there is a large-capacity capacitor. When the power-on is instantaneous, it is equivalent to a step signal at both ends of the capacitor. If the capacitor is directly added to both ends of the capacitor, the charging current of the capacitor is large, which will seriously affect the life of the capacitor. For this purpose, most of the inverters have added a soft-start circuit after the rectification section. According to this idea, in addition to the capacitance of the three inverters in the roving frame, a large-capacity capacitor is externally attached to the DC bus, so it is necessary to design a soft-start circuit to ensure the life of the inverter. The main idea is as follows: The external capacitor on the DC bus of the inverter is shown in Figure 2. The control end of the contactor is controlled by the PLC. When the power is turned on, the PLC delays for a period of time. After the capacitor is charged through the resistor R, the contactor is closed. Bypass resistor R.
4.2 Soft start electrical parameter calculation
5 Conclusion
Inverter drive roving machine multi-motor power failure synchronous braking is a special problem in the textile industry. At the time of power failure, the system has completely lost the external energy supply. In general, the inverter brake is completely invalid, and hundreds of spindles are broken, which requires long-time manual wiring to resume operation. The external busbar capacitor synchronous braking scheme discussed in this paper has positive practical significance, and the project has passed the research and development stage and performed well in practical applications.
