Application of Emerson CT EV3000 Inverter and Its Common DC Bus in Polyester Short Wire Drawing Unit

1. The working principle of the polyester short yarn drafting machine and the defects of the original design

The schematic diagram of the polyester filament yarn drawing and unifying machine is shown in Fig. 1. It is a chemical fiber composite machine that performs multi-unit transmission of polyester chemical fiber drafting and crimping, and the running speed between each unit machine maintains a certain ratio relationship. Finished chemical fiber draft curl forming. The third drafting machine and the curling machine drive motor are in an electric working state, and the first drafting machine and the second drafting machine

The drive motor is in a power generation state, that is, it controls the first drafting machine and the second drafting machine drive motor to complete the four-quadrant operation.

The traditional design is that one inverter controls a high-power motor and drags four unit machines through the long axis of the machine. The problems are: (1) The installation and adjustment of the machine's long side shaft is difficult, and the drafting rate accuracy is adjusted by the mechanical continuously variable transmission. Poor, not intuitive; (2) single motor operating parameters can not be accurately obtained; (3) difficult to achieve four-quadrant operation, which is difficult to adapt to the needs of a larger draft ratio.

2. System composition

The control system consists of the components shown in Figure 2. The system is composed of Emerson CT EV3000 vector inverter, chopping brake, braking resistor, contactor K1, K2, K3, K4 and some fast-melting components. The DC outputs of the four inverters are connected to each other to form a common DC bus, providing a path for the energy to flow on the DC bus of the transmission, making the synchronization and braking control of the Association Engine more flexible and convenient.

Figure 2 shows the composition of the control system

In order to ensure that the DC bus is connected to the inverter smoothly after power-on, or disconnected from the DC bus after the fault of the inverter to further reduce the fault range of the inverter, the inverter used in this application must have a signal of 24VDC or dry. Contact signal output, the output signal includes at least: (1) READY signal: the signal output is valid indicates that the inverter has no fault, the bus voltage is normal, and can accept the start command; (2) FAULT signal: the signal output indicates the inverter fault . The semiconductor fuses on the bus, the rated voltage is usually 700VDC, such as Bussman's FWP series or Gouldshawmut's A70P series, the rated current must take into account the maximum energy of the drive motor in electric or braking, under normal circumstances can be rated load 125% current can be. K is a DC contactor, such as ABB's EHDB series, rated voltage is 650VDC, and its rated current must also be determined according to the maximum current when the drive motor is braked. Under normal circumstances, 120% of rated load current can be selected.

3. The realization of control function

3.1 Characteristics of EV3000 Inverter

The EV3000 series inverter is a high-quality, multi-functional, low-noise vector control universal inverter. By decoupling the control of the flux current and torque current of the motor, the torque response can be quickly controlled and accurately controlled. High control accuracy for a wide range of speed control and torque control. With over-voltage, over-current, phase loss, overheating, overload, encoder breakage and other fault protection features to support emergency operation.

3.2 Control principle

Control block diagram shown in Figure 3. The principle is that (1) the speed reference signal is sent from the PLC to the inverters of each unit by the PROFIBUS bus after operation; (2) The PI adjustment is completed by using the built-in PID function of the inverter, which can be properly changed according to the operating conditions in the actual operation; ( 3) The encoder uses Japan Koyo high-reliability open collector output rotary encoder, 1000P/R, to achieve closed-loop operation.

3.3 Start and stop control of the inverter

The logic diagram of the start-stop control of the inverter start-stop control is shown in Fig. 4. The start-stop of the inverters of each unit consists of “no fault of the inverter”, “opening of the drafting oil pump” and “opening of the motor cooling fan”. , "motor from the brake", "system has been started" five-way signal control, five-way signal logic control completed by the PLC, and then by the PLC output signal to control each unit inverter.

3.4 Association Engine Speed ​​Control

The speed control of the Association Engine is based on the speed of the third drafting machine. By setting the ratio between adjacent units, the PLC will send the speed signal to the corresponding frequency converter via the PROFIBUS bus after the operation; the speed and magnification parameters The setting and display are realized on the Siemens TP177A touch screen, which greatly facilitates the operator to modify parameters and monitor the operation of the equipment.

3.5 main parameters of the inverter settings

Function Code Setting Parameter Remarks

F0.02 1 control method is closed-loop control

F0.03 6 Frequency setting method for communication given

F0.05 1 Run command for terminal control

F0.10 10S Acceleration Time Setting

F0.11 10S deceleration time setting

F5.11 0 Drive ready

F9.00 4:19200bps baud rate selection

F9.01 0 data format

F9.03 4 PPO Mode Selection

4 EV3000 Common DC Bus

4.1 EV3000 Common DC Bus

Connect the DC output terminals of the diode rectifier bridge of the voltage-type inverter to the inverter section. This configuration is called the common DC bus. The EV3000 common DC bus is a system configuration that interconnects the DC outputs of multiple EV3000 frequency converters to form a common DC bus structure. Its role is to provide the path for energy to flow between the DC busses of the drive, making one part in the electric state and the other in the inverter. State, the application of the system is more flexible and convenient.

4.2 Advantages of Common DC Bus

When one unit is in electric and the other is in inverter state, due to the utility of the common DC bus, energy can be circulated between the driving DC buses to realize the complementary feedback of energy and optimize the dynamic characteristics of the system, due to the use of common DC. A single brake can be used to brake multiple buses, which is more economical and easier to maintain than using a single drive alone. The DC voltage in the common DC bus is constant, and the capacitors store large capacity in parallel, which can increase the power factor of the system, reduce the harmonic current of the power grid, and increase the system power efficiency.

5 Concluding remarks

The application of EV3000 frequency converter and its common DC bus in the polyester short filament drawing and unifying machine realizes: (1) A frequency converter drags a unit motor to accurately detect the running state parameters of each unit motor. (2) The speed control system has high reliability, flexible control, and easy operation; (3) Four-quadrant operation, which can meet the needs of larger drafting ratios; (4) Common DC The use of busbars optimizes system dynamics and improves system stability.

references

(1) Emerson CT EV3000 High Performance Vector Control Inverter User Manual.

(2) Li Fangyuan “On the two braking methods of frequency converter”.