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Foreword: The steel belt conveyor system of the integrated steelyard of Baogang Iron Works adopts 132KW two motors (one master, one slave) for transmission. The original system uses a contactor to start. The length of the conveyor belt is about 500 meters. Under normal circumstances, direct start has no effect on the system. However, when an accidental failure occurs in the process of feeding, it will cause shutdown when the system is overhauled. It will be very difficult to start, causing the contactor to overheat and burn and even cause over-current. Causes a short circuit between phases. If the commonly used step-down soft-start method is adopted, since the starting torque is proportional to the square of the voltage, the heavy-load starting cannot be achieved at all. To this end, we use Emerson's EV3000 series of high-torque, high-precision inverter as the motor control core, with the EC20 series PLC to achieve the master-slave control of the two inverters to achieve the two motors with the same frequency or load balancing operation.
1, frequency conversion control system
1.1 System Parameters:
Belt motor 132KW, current 245A, quadrupole, speed 1480 R/MIN
The design uses EV3000-4T132G (high performance) series inverters. With EC20 series PLC and analog combination module 5AM (four-in, one-out), through the PLC for PID closed-loop control. The main frequency converter can be set with digital or analog settings. The output frequency of the main frequency inverter is used as the PID's given amount. The output frequency of the frequency converter is used as the PID feedback link, and the PID output is used as the slave frequency. The setpoint of the frequency converter allows the frequency of the master and slave frequency converters to operate in unison. Specific principles see Figures 1 to 5
1.2 Frequency Conversion Parameter Settings
Main frequency conversion:
F0.02=4 V/F control F0.03=0 Digital setting, given by the panel
F0.04=50 Host given F0.05=1 terminal control
F0.10=60S Acceleration time F0.11=20 Deceleration time
Because the site does not have the motor tuning operation (takeover can not be opened), so the control method uses V / F control, motor parameters F1.00-1.08 set by the actual motor parameters.
F2.09=1 The stop mode is free parking
F6.08=0 AO1 output signal is the actual operating frequency
F6.09=3 AO2 output signal is the actual operating current
F6.12=20% AO2 signal output bias is 20%
The specific reason is: Since the AO2 signal is sent to the computer room of the upstairs control station, the signal required by the control station PLC is 4-20MA. Therefore, when the inverter output current signal is 4MA, the corresponding actual current is 0; that is, 4MA/20MA=20%, and the output offset is 20%.
From the frequency conversion:
F0.02=4 V/F control F0.03=5 Analog setting, given by PLC
F0.05=1 terminal control
F0.10=60S Acceleration time F0.11=20 Deceleration time
F2.09=1 The stop mode is free parking
F6.08=0 AO1 output signal is the actual operating frequency
F6.09=3 AO2 output signal is the actual operating current
F6.12 = 20% AO2 signal output bias is 20%
2, PLC control system
2.1 PLC hardware configuration
It is composed of host EC20-1410BRA and analog combination EC20-5AM (four in and one out). One of the input channels is the actual operating frequency of the main inverter; the second channel is the actual operating frequency of the inverter, and the input signals are all 4-20MA; the output is the setpoint of the inverter, and the signal is 0-10V.
2.2 Frequency Control PID Program
LD SM1
TO 0 400 16#1 1 5AM module initialization
LD SM1
TO 0 600 16#3311 1 Input 1 and 2 channels are current signal 3 and 4 channels are closed.
LD SM1
TO 0 650 16#0 1 Output Channel is 0-10V signal
LD SM1
TO 0 500 16#1 1 Channel setting change allowed
LD SM1
TO 0 800 16#1 1 Input channel setting change confirmation
LD SM1
TO 0 801 16#1 1 Output channel setting change confirmation
LD SM0
FROM 0 100 D100 1 Read channel 1 value (main frequency operation frequency)
LD SM0
FROM 0 101 D101 1 Read channel 2 value (from inverter operation frequency)
LD SM0
MOV D101 D21 Channel 2 value as PID feedback value.
LD SM0
TO 0 0 D22 1 PID output signal is output from the output channel (as a slave frequency conversion reference)
LD SM0
CALL PID_EXE calls PID executive
LD SM0
CALL PID_SET calls PID setup program
PID subroutine
LD SM0
PID D20 D21 D0 D22 //The PID instruction generation formula of the subroutine PID S1 S2 S3 D
LD SM0
MOV D100 D20 //Set target value
MOV 10 D0 // sampling time (Ts) is in the range of 1 to 32767 (ms) but the time value shorter than the operation period cannot be executed
MOV 33 D1 //action direction
MOV 0 D2 //filter time constant
MOV 1000 D3 //Proportional Gain (Kp) MOV 1 D4 // Integration Time TI MS
MOV 0 D5 //Differential gain (KD) MOV 0 D6 //Differential time
MOV 0 D15 //Input variation MOV 0 D16 //Input variation
MOV 2000 D17 //Output upper limit set MOV 0 D18 //Output limit setting
2.3 Actual parameter adjustment settings
Finally, after several modifications and debugging, it was determined that the proportional coefficient was 10, the integration time was 100 milliseconds, and the derivative time was zero. After the operation was found to be able to meet the production process at the site, the main and slave belts started smoothly.
3, chain control
Chain control mainly achieves the following functions:
First, the main and slave frequency converters start together and stop together.
2. If any inverter fails, another inverter stops immediately.
The realization of chain control through the intermediate relay (Design Institute design, can be achieved through PLC)
4, the actual operation:
After 2 months of operation, the system was able to operate very stably. The starting current of the belt was about 120A. The starting frequency of the master and slave inverters was exactly the same. The starting frequency of the master inverter was slightly greater than that of the slave inverter, and the start was stable and reliable. Production requirements. The EV3000 frequency changer setting panel has the Chinese display function, and the parameter setting is very simple, facilitates the on-the-spot maintenance; This series frequency changer is very strong in the overload capacity. Due to the initial commissioning of the inverter, the brake of the belt motor did not open, and the pump motor of the speed reducer did not start. At that time, the overload current reached almost 450A, and it operated for more than ten seconds under the high current limit. The inverter did not have any malfunction.
references
1 Emerson Corporation EV3000 Series Universal Inverter Emerson Network Power Co., Ltd.
2 New PID Control and Its Application Machinery Industry Press Tao Yonghua
3EC20 System Manual Emerson Network Power Co., Ltd.
4 General-purpose Inverters and Their Applications Machinery Industry Press Han Anrong
5 Motor Drive and Control Xi'an Electronic Science and Technology University Press Liu Baolu
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