Application cases of FD500 frequency converter on large circular machines
1.Introduction to the Circular Knitting Machine process
(1)Introduction to the Circular Knitting Machine
The circular knitting machine (as shown in Figure 1) is a device that wears cotton yarn into cylindrical fabric. It is mainly used for weaving various pile knitted fabrics, T-shirt fabrics, and various patterned fabrics with holes, etc. According to structure, they can be classified into single-sided circular machines and double-sided circular machines, and are widely used in the textile industry.
(2) Technological requirements
The frequency converter is required to have strong environmental resistance. Since the working environment in the field has a high temperature and cotton fibers are prone to cause the cooling fan to run in a stuck state and be damaged, or the cooling holes to get blocked.
It is required to have a flexible point-run operation function. Point-run buttons are installed in many parts of the equipment, and the frequency converter is required to respond quickly.
In terms of speed control, there are three speeds. One is the point-run speed, which is usually around 6Hz; the second is the normal weaving speed, with the maximum frequency reaching 70Hz; the third is the low-speed winding operation, requiring a frequency of around 20Hz.
During the operation of the large circular loom, it is strictly prohibited for the motor to reverse or rotate. Otherwise, the needles on the needle bed will be bent or broken. For large circular looms with single-phase bearings, this can be disregarded. If the forward and reverse rotation of the system completely depends on the forward and reverse rotation of the motor, then on the one hand, it is necessary to be able to prohibit the reverse rotation, and on the other hand, a DC braking system needs to be set up to eliminate the rotation.
2.On-site requirements and commissioning plans
(1) On-site requirements
The requirements for the control functions of frequency converters in the large circular machine industry are relatively simple. Generally, it is controlled by terminals for starting and stopping, or by analog signals to set the frequency, or by using multiple speed settings to set the frequency. It is required that point operation or low-speed operation should be quick. Therefore, it is required that the frequency converter can generate a large low-frequency torque when controlling the motor at a low frequency. Generally, in the application of large circular machines, the frequency converter can meet the requirements in V/F mode.
The solution we adopted is: FGI FD500 series frequency converter. Power: 3.7KW and 5.5KW.
3.Debug parameters and instructions
(1) Debugging parameter setting
P0.1 = 2 VF mode
P0.2 = 1 External terminal control
P0.3 = 3 External voltage signal for frequency input channel
P0.17 = 5 Acceleration time 5 seconds
P0.18 = 0.8 Deceleration time 0.8 seconds
P4.01 = 4 Set DI2 as the forward jog point
P8.00 = 6 Set jog frequency to 6 Hz
P8.01 = 3.5 Set jog acceleration time to 3.5 seconds
P8.0 = 1.5 Set jog deceleration time to 1.5 seconds
(2) Debugging precautions:
First, perform a test run to confirm the direction of the motor.
Regarding the vibration and slow response during the test run, the acceleration and deceleration time for the test run needs to be adjusted according to the requirements.
The low-frequency torque can be improved by adjusting the carrier and torque boost.
If the air duct is clogged with cotton fibers and the fan is running continuously, it will cause poor heat dissipation of the frequency converter. This situation occurs frequently. Currently, most frequency converters simply skip the heat alarm and continue to use after manually removing the cotton fibers from the air duct.
